White Paper: Planning for Exchange 2007 Unified Messaging - Part 1

 

Joey Masterson, Technical Writer, Microsoft Exchange Server

October 2007

Summary

This white paper provides the general information that you need to deploy Microsoft Exchange Server 2007 Unified Messaging (UM). This includes hardware and software considerations in addition to scalability and availability information. After you have read the Unified Messaging Technical Overview white paper, read this white paper to learn about the necessary planning information that will help guarantee a successful Unified Messaging deployment.

Applies To

Microsoft Exchange Server 2007

Table of Contents

• Introduction

• Planning for Unified Messaging

• Unified Messaging Architecture

• Overview of Unified Messaging Server Topologies

• Unified Messaging Telephony Concepts and Components

  • Understanding Protocols, Ports and Services in Unified Messaging

  • Understanding PBX and IP PBX Configurations

• Overview of Unified Messaging Components

  • Understanding Unified Messaging Incoming Call Handling

  • Understanding Unified Messaging Subscriber Access

  • Understanding Unified Messaging Audio Prompts

  • Understanding Unified Messaging Audio Codecs

  • Understanding Custom Prompt Distribution

  • Understanding Unified Messaging Languages

  • Understanding Automatic Speech Recognition Directory Lookups

  • Understanding the DTMF Interface

  • Understanding Storage Quotas and Voice Mail

  • Understanding Unified Messaging VoIP Security

  • Understanding Faxing in Unified Messaging

  • Understanding Operator Transfers in Unified Messaging

  • Understanding Outdialing

  • Understanding Dial Codes, Number Prefixes, and Number Formats

• Overview of Unified Messaging Active Directory Objects

  • Overview of Unified Messaging Dial Plans

  • Understanding Unified Messaging Dial Plans

  • Understanding Unified Messaging Mailbox Policies

  • Understanding Unified Messaging IP Gateways

  • Understanding Unified Messaging Hunt Groups

  • Understanding Unified Messaging Auto Attendants

  • Understanding Unified Messaging Servers

  • Understanding Unified Messaging Users

• Overview of the Unified Messaging Call Processing

  • Unified Messaging Voice and Fax Call Processing

  • Unified Messaging Outlook Voice Access Call Processing

  • Unified Messaging Auto Attendant Call Processing

  • Unified Messaging Play on Phone Call Processing

• IP Gateway Support

  • IP PBX Support

  • PBX Support

• Unified Messaging Server Scalability

• Unified Messaging Availability

Introduction

The Microsoft Exchange Server 2007 Unified Messaging server role enables Unified Messaging for an Exchange 2007 organization. Unified Messaging lets users access their Exchange 2007 mailbox over any telephone for e-mail, voice mail, fax messages, and calendaring and contact information.

Migrating to Exchange 2007 Unified Messaging from your current voice mail solution or implementing a new voice mail system by using Exchange 2007 Unified Messaging can be a complex process. Planning and deployment requires the coordination of telephony, IT, and Exchange administrators. This white paper discusses how to develop a plan to deploy Exchange 2007 Unified Messaging for your organization.

Important

We recommend that all customers who plan to deploy Exchange 2007 Unified Messaging obtain the help of a Unified Messaging specialist. This will help guarantee a smooth transition from a legacy voice mail system. Rolling out a new UM deployment or performing an upgrade of an existing legacy voice mail system requires significant knowledge of Private Branch eXchanges (PBXs) and Exchange 2007 Unified Messaging. For more information about who to contact, see the Microsoft Exchange Server 2007 Unified Messaging (UM) Specialists Web site.

Planning for Unified Messaging

When you plan your Exchange 2007 Unified Messaging deployment, you must consider design and other issues that may affect your ability to reach your organizational goals when you deploy Exchange 2007 Unified Messaging.

Generally, the simpler the Unified Messaging topology, the easier Unified Messaging is to deploy and maintain. Install as few Unified Messaging servers and create as few Unified Messaging objects in the Active Directory directory service as you have to support your business and organizational goals. Large enterprises that have complex network and telephony environments, multiple business units, or other complexities will require more planning than smaller organizations that have more straightforward Unified Messaging needs.

There are many areas that you must consider or evaluate to be able to successfully deploy Unified Messaging. You must understand the different aspects of Exchange 2007 Unified Messaging and each component and feature so that you can plan your Unified Messaging infrastructure and deployment appropriately.

Allocating time to plan and work through these issues will help prevent problems when you deploy Unified Messaging in your organization.

The following are some areas that you should consider and evaluate when planning for Exchange 2007 in your organization:

• Your business needs for Unified Messaging

• Your telephony network and your current voice mail system

• Your current data network design

• Your current Active Directory environment

• The number of users who you must support

• The number of Unified Messaging servers you will need

• The storage requirements for users

• The placement of IP gateways, telephony equipment, and Unified Messaging servers

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Who Should Read This White Paper

Information technology and telephony professionals who are responsible for planning and designing Exchange messaging systems that include Exchange 2007 Unified Messaging for their companies should read this white paper. Such professionals may include the following:

• System architects   Responsible for designing the overall server infrastructure, developing server deployment strategies and policies, and contributing to networking connectivity design.

• Information technology managers   Technical decision makers, who also manage the Information Technology staff responsible for the infrastructure, the desktop and server deployment, and server administration and operations across sites.

• Systems administrators   Responsible for planning and deploying technology across Microsoft Windows servers and evaluating and recommending new technology solutions.

• Messaging administrators   Responsible for implementing and managing organizational messaging.

• Telephony administrators and consultants   Responsible for implementing and managing an organizations telephony infrastructure.

Unified Messaging Architecture

When you install the Unified Messaging (UM) server role on a computer that is running Microsoft Exchange Server 2007, several UM-specific components and services are installed. The Unified Messaging services and components that are installed by Setup enable a Unified Messaging server to answer and process incoming voice and fax calls and enable users to interact with the Unified Messaging system by using Outlook Voice Access or by hearing a UM auto attendant when they call in to the UM system. This topic discusses the interaction between these UM components and services and how the services and components provide the features that are offered by Unified Messaging.

Overview of Unified Messaging Services

The features and components of Unified Messaging rely on the functionality of two Exchange 2007 services: the Microsoft Exchange Unified Messaging service (UMservice.exe) and the Microsoft Exchange Speech Engine service (SpeechService.exe). The Service Control Manager controls and monitors both of these services and their related processes.

The Microsoft Exchange Unified Messaging service enables voice and fax messages to be stored in an Exchange 2007 mailbox and gives users telephone access to e-mail, voice mail, calendar, and contacts. If you stop this service, Unified Messaging features will not be available for users in your organization. For the Microsoft Exchange Unified Messaging service to work, the Microsoft Exchange Speech Engine service must already be started and functioning correctly.

The Microsoft Exchange Speech Engine service controls the following:

• The dual tone multi-frequency (DTMF), also known as touchtone, interface

• Automatic Speech Recognition (ASR) that is used with the Voice User Interface (VUI) in Outlook Voice Access

• The Text-to-Speech (TTS) engine that reads e-mail, voice mail, and calendar items and plays the menu prompts for callers

When the Microsoft Exchange Unified Messaging service and Microsoft Exchange Speech Engine service are starting, they each create their own worker processes: the UM worker process (UMWorkerProcess.exe) and the Speech Engine service worker process (SESWorker.exe). Each UM worker process enables the Microsoft Exchange Unified Messaging service and the Microsoft Exchange Speech Engine service to interact to provide Outlook Voice Access and call answering. The Speech Engine service worker process provides the TTS engine features, enables callers to use both Outlook Voice Access interfaces, and plays the system prompts for callers. For more information about Outlook Voice Access, see Understanding Unified Messaging Subscriber Access later in this white paper. For more information about Unified Messaging system prompts, see Understanding Unified Messaging Audio Prompts later in this white paper.

The following figure illustrates the relationships between Unified Messaging components.

Unified Messaging architecture

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Service Ports

The Microsoft Exchange Unified Messaging service and the UM worker process use multiple Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) service ports to communicate with IP gateways and the Speech Engine service worker process that is created by the Microsoft Exchange Speech Engine service at startup. The Microsoft Exchange Unified Messaging service and the UM worker process use Session Initiation Protocol (SIP) over TCP. By default, the Microsoft Exchange Unified Messaging service listens on TCP port 5060 in unsecured mode and TCP port 5061 when Mutual Transport Layer Security (MTLS) is used. Each UM worker process that is created listens on TCP port 5065 and 5066. However, when an IP gateway or IP sends Realtime Transport Protocol (RTP) traffic to the Speech Engine service worker process, the IP gateway or IP PBX will use a valid UDP port that ranges from 1024 through 65535.

A TCP control port is also used on a Unified Messaging server. When a UM worker process is created, the Microsoft Exchange Unified Messaging service passes the appropriate configuration options to the UM worker process. The configuration options that are sent include the parameters for the TCP control port number that is used for communication between the Microsoft Exchange Unified Messaging service and the UM worker process. The TCP control port that is chosen will fall between TCP ports 16,000 to 17,000.

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Unified Messaging Services

The Microsoft Exchange Unified Messaging service is one of the two services that provide Unified Messaging services for your network. The Microsoft Exchange Unified Messaging service performs the following functions:

• Retrieves the dial plan configuration from the Active Directory directory service

• Loads the configuration information for monitoring Unified Messaging worker processes from the UmRecycleConfig.xml file

• Initializes the UM Worker Process Manager and the startup of a UM worker process

• Registers SIP endpoints

The Microsoft Exchange Unified Messaging service first accepts all incoming connections, and then reroutes those requests to a UM worker process that handles the incoming request. In addition, the Microsoft Exchange Unified Messaging service monitors any UM worker process that is created and ensures that the UM worker process is functioning correctly. If a UM worker process becomes unresponsive, the Microsoft Exchange Unified Messaging service stops the UM worker process, and then create a new UM worker process to replace it.

Note

By default, each UM worker process will be recycled every seven days or 604,800 seconds. The setting can be found in the \bin\umrecyclerconfig.xml file.

The Microsoft Exchange Unified Messaging service works with the Microsoft Exchange Speech Engine service to implement all the telephony features that are offered by Exchange 2007 Unified Messaging. The Microsoft Exchange Unified Messaging service handles call control and interacts with the Microsoft Exchange Speech Engine service to handle the incoming media streams that are negotiated in the SIP signaling information between the Microsoft Exchange Unified Messaging service and a SIP-enabled telephony device such as an IP gateway or IP PBX. The following events occur when an incoming call is initiated by the Microsoft Exchange Unified Messaging service:

1. A call session is initiated by the Microsoft Exchange Unified Messaging service.

2. The Microsoft Exchange Unified Messaging service redirects the call to a UM worker process.

3. The UM worker process requests that a media session be established with the Microsoft Exchange Speech Engine service, and then the UM worker process relays the media information back to the caller.

4. The Speech Engine Service worker process that is created by the Microsoft Exchange Speech Engine service provides a UDP port for the RTP stream.

5. The UM worker process uses the SIP signaling information to inform the Speech Engine Services worker process to end the call session when the RTP media stream is no longer needed.

Unified Messaging Worker Process

A Unified Messaging worker process is a process that is created during the startup of the Microsoft Exchange Unified Messaging service. UM worker processes interact with all incoming and outgoing requests that have been received by the Microsoft Exchange Unified Messaging service.

The Unified Messaging Worker Process Manager is also a component of the Microsoft Exchange Unified Messaging service. The UM Worker Process Manager handles the creation and monitoring of all the UM worker processes that are created. The UM Worker Process Manager creates new instances of a UM worker process based on the configuration settings that are located in the UmRecyclerConfig.xml file and also monitors the health of these processes. As a new incoming call arrives, the UM Worker Process Manager determines the appropriate instance of a UM worker process to which to redirect the call. The UM worker process then interacts with the Microsoft Exchange Speech Engine service components to correctly process incoming and outgoing requests. The UM worker process is responsible for the following startup tasks:

• Allocation of the runtime management objects

• Loading of the UM configuration from UMConfig.xml

• Initialization of the fax job listener

• Registration of the process with the Microsoft Exchange Speech Engine service

• Initialization of Simple Mail Transfer Protocol (SMTP) message submission

For more information about Voice over IP (VoIP) security in Unified Messaging, see Understanding Unified Messaging VoIP Security later in this white paper.

The Unified Messaging worker process also contains a fax provider that lets users receive fax messages in their Exchange 2007 mailbox. The fax provider that is included in a UM worker process uses the T.38 protocol over UDP Transport Layer (UDPTL). This UM worker process transfers the fax message and then creates and processes the compressed Tagged Image File Format (TIFF) of the fax message that is received. For more information about faxing in Unified Messaging, see Understanding Faxing in Unified Messaging later in this white paper.

Microsoft Exchange Speech Services

The Microsoft Exchange Speech Engine service is an embedded speech engine that is installed when you install the Unified Messaging server role. This Microsoft Exchange Speech Engine service is an Interactive Voice Response (IVR) platform that provides speech recognition capability that is used to recognize user input and provide Text-to-Speech (TTS) capabilities.

The applications in an IVR platform communicate with end users through a telephony or VoIP network. The Microsoft Exchange Speech Engine service supports SIP and RTP for telephony connectivity and TLS. For Unified Messaging, when an incoming call is received, the Microsoft Exchange Speech Engine service processes the RTP stream that is associated with the call, and then passes the information and events to the UM worker process that is managing the SIP connection. The Microsoft Exchange Speech Engine service supports the following features in Unified Messaging:

• Automatic Speech Recognition (ASR) input recognition

• DTMF, or touchtone, input recognition

• The TTS conversion process

• Recording e-mail and voice mail messages

• Playing e-mail and voice mail messages to the user

For more information about Automatic Speech Recognition, see Understanding Automatic Speech Recognition Directory Lookups later in this white paper. For more information about the TTS engine, see Understanding Unified Messaging Audio Prompts later in this white paper.

When the Microsoft Exchange Speech Engine service is starting, it creates the Speech Engine Service worker process. During call flow, the Speech Engine Service worker process is responsible for recognizing touchtone or voice input from the user. For example, if a caller uses ASR or voice inputs to navigate the main menu, the following steps occur:

1. An Outlook Voice Access user calls a subscriber access number and logs on to their mailbox or an outside caller dials in to a number that is configured to have a UM auto attendant and they use ASR or voice inputs to navigate the main menu.

2. When a call is received by a Unified Messaging server, the Unified Messaging server determines whether the menu is speech-enabled. If the menu is speech-enabled, the Unified Messaging server uses specific prompts and grammars.

3. The UM worker process notifies the Speech Engine service worker process to begin recognition based on the grammar file that is needed. For this example, the main menu is needed. Therefore, the Speech Engine service worker process loads the mainmenu.grxml file. The Microsoft Exchange Speech Engine service plays the main menu prompts over the telephone to the Outlook Voice Access user.

4. For example, the user may respond by saying “e-mail”. The voice traffic that is created is sent over an RTP stream and is received by the Speech Engine Service worker process. The Speech Engine Service worker process, which has already loaded the mainmenu.grxml file, compares the voice recognition results to the contents in the file. The result is sent to the UM worker process.

5. The UM worker process determines what transition to make based on the results from the Speech Engine Service worker process. For this example, the next transition state is to play the menu of e-mail options to the user.

6. The correct activity manager is loaded into memory for playing the e-mail menu. The corresponding grammar file for the e-mail menu, which is email.grxml, is then loaded by the Speech Engine Service worker process.

7. The UM worker process sends a request to the Microsoft Exchange Speech Engine service to play the corresponding prompts for the e-mail menu.

A similar series of events occurs when a caller is using DTMF, or touchtone, inputs to navigate the menus. Handling of DTMF input resembles handling voice inputs, except that the Speech Engine Service worker process notifies the UM worker process when DTMF events are detected in the RTP stream. The data that is passed by this event corresponds to the number pressed by the caller. For more information about the DTMF interface, see Understanding the DTMF Interface later in this white paper.

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Overview of Unified Messaging Server Topologies

Microsoft Exchange Server 2007 supports a server architecture that distributes server tasks among different server roles. In this kind of architecture, a computer that is running Exchange Server 2007 that has the Unified Messaging server role installed accepts incoming calls. The Unified Messaging server then routes the messages to the appropriate server for processing. This could be the Client Access server, the Mailbox server, or the Hub Transport server. The server that has the Hub Transport server role installed was formerly known as a bridgehead server.

This topic describes the relationship between the Exchange Server 2007 Unified Messaging servers on a typical network and the telephony components in an organization.

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Unified Messaging Topology That Has a Single PBX

The following figure illustrates an Exchange Server 2007 Unified Messaging topology that contains a single Private Branch eXchange (PBX).

Exchange Server 2007 UM topology that has a single PBX

Unified Messaging Topology That Has Multiple PBXs

The following figure illustrates an Exchange Server 2007 Unified Messaging topology that contains multiple PBXs.

Exchange Server 2007 UM topology that has multiple PBXs

For more information about telephony concepts, see Unified Messaging Telephony Concepts and Components later in this white paper.

For more information about how to deploy Exchange Server 2007 Unified Messaging, see Post-Installation Tasks.

Unified Messaging Telephony Concepts and Components

If you are planning and deploying Microsoft Exchange Server 2007 Unified Messaging (UM) on your network, you must broaden your understanding and knowledge of Unified Messaging and telephony networks. This topic provides an overview of telephony infrastructure concepts and components and will help you plan and deploy a server that is running Exchange 2007 Unified Messaging.

In earlier versions of Microsoft Exchange, the Exchange administrator's main responsibility was managing e-mail messages and, sometimes, managing a network infrastructure.

However, the earlier versions of Exchange did not have unified messaging capabilities. The Exchange Server version 5.5, Exchange 2000 Server, and Exchange Server 2003 administrator had to focus only on the Exchange environment and the network infrastructure and relied heavily on telephony consultants to manage their telephony environment and infrastructure.

To successfully deploy a Unified Messaging server, you must have a good understanding of basic telephony concepts and telephony components. After you gain a good understanding of telephony basics, you can successfully integrate Exchange 2007 Unified Messaging into an Exchange 2007 organization.

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Telephony Concepts and Components

To successfully deploy an Exchange 2007 Unified Messaging server in an Exchange organization, the Exchange administrator must become knowledgeable about data networking concepts and telephony terminology and concepts. This topic provides an overview of networking and telephony components and concepts that you must have to understand Unified Messaging. These include the following:

• Circuit- and packet-switched networks

• Private Branch eXchange (PBX)

• Internet Protocol Private Branch eXchange (IP PBX)

• Voice over Internet Protocol (VoIP)

• IP gateways

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Circuit-Switched Networks

In circuit-switched networks, such as the Public Switched Telephone Network (PSTN), multiple calls are transmitted across the same transmission medium. Frequently, the medium that is used in the PSTN is copper. However, fiber optic cable might also be used.

A circuit-switched network is a network in which there exists a dedicated connection. A dedicated connection is a circuit or channel that is set up between two nodes so that they can communicate. After a call is established between two nodes, the connection may be used only by these two nodes. When the call is ended by one of the nodes, the connection is canceled.

Note

PSTN is a grouping of the world's public circuit-switched telephone networks. This grouping resembles the way that the Internet is a grouping of the world's public IP-based packet-switched networks.

There are two basic types of circuit-switched networks: analog and digital. Analog was designed for voice transmission. For many years, the PSTN was only analog, but today, circuit-based networks such as the PSTN have transitioned from analog to digital. To support an analog voice transmission signal over a digital network, the analog transmission signal must be encoded or converted into a digital format before it enters the telephony WAN. On the receiving end of the connection, the digital signal must be decoded or converted back into an analog signal format.

There are advantages and disadvantages to circuit-switched networks. Circuit-switched networks have several disadvantages. Circuit-switched networks can be relatively inefficient, because bandwidth can be wasted. This is not the case when VoIP is used on a packet-switched network. VoIP shares the available bandwidth with all other network applications and makes more efficient use of the available bandwidth. Another disadvantage to circuit-switched networks is that you have to provision for the maximum number of telephone calls that will be required for peak usage times and then pay for the use of the circuit or circuits to support the maximum number of calls.

Circuit switching has one big advantage over packet-switched networks. In a circuit-switched network when you use a circuit, you have the full circuit for the time that you are using the circuit without competition from other users. This is not the case with packet switched networks.

Note

Synchronous Digital Hierarchy (SDH) has become the primary transmission protocol for most PSTN networks. SDH is carried over fiber optic networks.

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Packet-Switched Networks

Packet switching is a technique that divides a data message into smaller units that are called packets. Packets are sent to their destination by the best route available, and then they are reassembled at the receiving end.

In packet-switch networks such as the Internet, packets are routed to their destination through the most expedient route, but not all packets traveling between two hosts travel the same route, even those from a single message. This almost guarantees that the packets will arrive at different times and out of order. In a packet-switched network, packets (messages or fragments of messages) are individually routed between nodes over data links that may be shared by other nodes. With packet switching, unlike circuit switching, multiple connections to nodes on the network share the available bandwidth.

Note

With circuit switching, all packets go to the receiver in order and along a single path.

Packet-switched networks exist to enable data communication on the Internet throughout the world. A public data network or packet-switched network is the data counterpart to the PSTN.

Packet-switched networks are also found in such network environments as LAN and WAN networks. A WAN packet-switched environment relies on telephone circuits, but the circuits are arranged so that they retain a permanent connection with their end point. In a LAN packet-switched environment, such as with an Ethernet network, the transmission of the data packets relies on packet switches, routers, and LAN cables. In a LAN, the switch establishes a connection between two segments only long enough to send the current packet. Incoming packets are saved to a temporary memory area or buffer in memory. In an Ethernet-based LAN, an Ethernet frame contains the payload or data portion of the packet and a special header that includes the media access control (MAC) address information for the source and destination of the packet. When the packets arrive at their destination, they are put back in order by a packet assembler. A packet assembler is needed because of the different routes that the packets may take.

Packet-switched networking has made it possible for the Internet to exist and, at the same time, has made data networks—especially LAN-based IP networks—more available and widespread.

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PBX

A legacy PBX is a telephony device that acts as a switch for switching calls in a telephony or circuit-switched network.

Note

A legacy PBX is a PBX that cannot pass IP packets. In many businesses, legacy PBXs have been replaced by IP PBXs.

A PBX is a telephony device that is used by most medium- and larger-sized companies. A PBX enables users or subscribers of the PBX to share a certain number of outside lines for making telephone calls that are considered external to the PBX. A PBX is a much less expensive solution than giving each user in a business a dedicated external telephone line. Telephone sets, in addition to fax machines, modems, and many other communication devices, can be connected to a PBX.

The PBX equipment is typically installed at a business's premises and connects calls between the telephones located and installed in the business site. A limited number of outside lines, also known as trunk lines, are typically available for making and receiving calls that are external to the business from an external source such as the PSTN.

Internal business calls made to external telephone numbers by using a PBX are made by dialing 9 or 0 in some systems followed by the external number. An outgoing trunk line is automatically selected to complete the call. Conversely, the calls placed between users within the business do not ordinarily require special dialing digits or use of an external trunk line. This is because the internal calls are routed or switched by the PBX between telephones that are physically connected to the PBX.

In medium- and larger-sized businesses, the following PBX configurations are possible:

• A single PBX that supports the whole business.

• A grouping of two or more PBXs that are not networked or connected to each other.

• A grouping of two or more PBXs that are connected together or networked.

Note

An Exchange 2007 Unified Messaging dial plan can span more than one PBX and one IP gateway.

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IP PBX

An IP PBX is a Private Branch eXchange (PBX) that supports the IP protocol to connect phones by using an Ethernet or packet-switched LAN and sends its voice conversations in IP packets. A hybrid IP PBX supports the IP protocol for sending voice conversations in packets, but also connects traditional analog and digital circuit-switched Time Division Multiplex (TDM) telephones. An IP PBX is telephone switching equipment that resides in a private business instead of the telephone company.

IP PBXs are frequently easier to administer than legacy PBXs, because administrators can easily configure their IP PBX services by using an Internet browser or another IP-based utility. Plus, no additional wiring, cabling, or patch panels must be installed. With an IP PBX, moving an IP-based telephone is as simple as unplugging a telephone and plugging it in at a new location, instead of the costly service calls to move a telephone from legacy PBX vendors. Additionally, businesses that own an IP PBX do not have the additional infrastructure costs that are required to maintain and manage two separate circuit-switched and packet-switched networks.

VoIP

Voice over Internet Protocol (VoIP) is a technology that contains hardware and software that enables people to use an IP-based network as the transmission medium for telephone calls. In VoIP, voice data is sent in packets by using IP instead of by traditional circuit transmissions or the circuit-switched telephone lines of the PSTN. An IP gateway that you connect to your IP network uses VoIP to send voice data packets between an Exchange 2007 Unified Messaging server and a PBX system.

IP gateways

An IP gateway is a third-party hardware device or product that connects a legacy PBX to your LAN. The IP gateway lets the PBX system communicate with your Exchange 2007 Unified Messaging server that is running IP.

Note

The IP gateway can also connect to PBX systems that use VoIP instead of PSTN circuit-switched protocols.

Exchange 2007 Unified Messaging relies on the gateway's abilities to translate or convert TDM or telephony circuit-switched based protocols like ISDN and QSIG from a PBX to IP- or VoIP-based protocols like Session Initiated Protocol (SIP), Real-Time Transport Protocol (RTP), or T.38 for Real-Time Facsimile Transport. The IP gateway is integral to the functionality and operation of Unified Messaging.

Important

After you install the IP gateway, you must create an IP Gateway object in the Active Directory directory service to represent the IP gateway. After you have created a UM IP Gateway object, the Unified Messaging server associated with the UM IP gateway will send a SIP OPTIONS request to the IP gateway to ensure that the IP gateway is responsive. If the IP gateway does not respond to the SIP OPTIONS request from the Unified Messaging server, the Unified Messaging server will log an event with ID 1088 stating that the request failed. To resolve this issue, ensure that the IP gateway is available and online and that the Unified Messaging configuration is correct.

For more information about IP PBX and PBX configurations, see Understanding PBX and IP PBX Configurations later in this white paper.

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Understanding Protocols, Ports and Services in Unified Messaging

Microsoft Exchange Server 2007 Unified Messaging (UM) requires that several Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) ports be used to establish communication between Exchange 2007 servers and other devices. By allowing access through these IP ports, you enable Unified Messaging to function correctly. This topic discusses the TCP and UDP ports that are used in Exchange 2007 Unified Messaging.

UM Protocols and Services

Exchange 2007 Unified Messaging features and services rely on static and dynamic TCP and UDP ports to ensure correct operation of the computer that is running the Unified Messaging server role.

Session Initiation Protocol

Session Initiation Protocol (SIP) is a protocol that is used for initiating, modifying, and ending an interactive user session that involves multimedia elements such as video, voice, instant messaging, online games, and virtual reality. It is one of the leading signaling protocols for Voice over IP (VoIP), together with H.323. Most VoIP standards-based solutions use either H.323 or SIP. However, several proprietary designs and protocols also exist. The VoIP protocols typically support features such as call waiting, conference calling, and call transfer.

SIP clients such as IP gateways and IP Private Branch eXchanges (PBXs) can use TCP and UDP port 5060 to connect to SIP servers. SIP is used only for setting up and tearing down voice or video calls. All voice and video communications occur over Realtime Transport Protocol (RTP).

Real-time Transport Protocol

RTP defines a standard packet format for delivering audio and video over a given network, such as the Internet. RTP carries only voice/video data over the network. Call setup and tear-down are generally performed by the SIP protocol.

RTP does not require a standard or static TCP or UDP port to communicate with. RTP communications occur on an even UDP port, and the next higher odd port is used for TCP communications. Although there are no standard port range assignments, RTP is generally configured to use ports 16384 through 32767. It is difficult for RTP to traverse firewalls because it uses a dynamic port range.

T.38

T.38 is a faxing standard and protocol that enables faxing over an IP-based network. The IP-based network then uses Simple Mail Transfer Protocol (SMTP) and MIME to send the message to a recipient's mailbox. T.38 allows for IP fax transmissions for IP-enabled fax devices and fax gateways. The devices can include IP network-based hosts such as client computers and printers. In Exchange 2007 Unified Messaging, the fax images are separate documents encoded as Tagged Image File Format (TIFF) images and attached to an e-mail message. Both the e-mail message and the TIFF attachment are sent to the recipient's Exchange 2007 UM-enabled mailbox.

UM Web Services

The Unified Messaging Web services that are installed on a Client Access server use IP for network communication between a client, the Unified Messaging server, the Client Access server, and computers that are running other Exchange 2007 server roles. There are several Exchange 2007 Outlook Web Access and Microsoft Office Outlook 2007 client features that rely on UM Web Services to operate correctly.

The following Unified Messaging client features rely on UM Web Services:

• The voice mail options that are available with Exchange 2007 Outlook Web Access, including the Play on Phone feature and the ability to reset a PIN.

• The Play on Phone feature found in the Outlook 2007 client.

Note

When an organization uses the Play on Phone and other client features in Exchange 2007 Unified Messaging, a computer that is running the Client Access, Hub Transport, and Mailbox server roles within the same Active Directory site is required in addition to the computer or computers that have the Unified Messaging server role installed.

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Port Assignments

The following table shows the IP ports that Unified Messaging uses for each protocol and whether the IP ports that are used for each protocol can be changed.

IP Ports that are used for Unified Messaging protocols

Protocol	TCP Port	UDP Port	Can ports be changed?
SIP - UM Service	5060 (TCP) 5061 (MTLS)		Ports are hard-coded and cannot be set by using the XML configuration file.
SIP - Worker Process	5065 and 5066		Ports are set by using the XML configuration file.
RTP		Port range above 1024	The range of ports can be changed in the registry.
T.38		Dynamic port above 1024	Ports are defined by the system.
UM Web Service	Dynamic port above 1024		Ports are defined by the system.

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Understanding PBX and IP PBX Configurations

Increasingly, organizations are purchasing, installing, and maintaining the hardware components, such as Private Branch eXchanges (PBXs) or IP PBXs, which are required to support their own telephony system. Many organizations are buying their own telephony equipment and training their staff to reduce expenses that are associated with maintaining their telephony systems, and because they want more control over the telephony features that they offer.

For an organization to own and maintain their telephony network, they must buy the required telephony hardware components. They must also consider the day-to-day maintenance of the telephony equipment and the training that is required for their staff to support their telephony system. This topic discusses the different types of telephony business or organizational systems, the telephony hardware components that are required, and gives examples of the different types of telephony configurations.

Important

We recommend that all customers who plan to deploy Microsoft Exchange Server 2007 Unified Messaging (UM) obtain the help of a Unified Messaging specialist. This will help ensure a smooth transition from a legacy voice mail system. Rolling out a new UM deployment or performing an upgrade of an existing voice mail system requires significant knowledge about PBXs, IP PBXs, and Exchange 2007 Unified Messaging. For more information about who to contact, see the Microsoft Exchange Server 2007 Unified Messaging (UM) Specialists Web site.

Overview of Telephony Systems

In circuit-switched networks, such as the Public Switched Telephone Network (PSTN), multiple calls are transmitted across the same transmission medium. Frequently, the medium that is used in the PSTN is copper. However, fiber optic cable might also be used.

A circuit-switched network is a network in which there exists a dedicated connection. A dedicated connection is a circuit or channel that is set up between two nodes so that they can communicate. After a call is established between two nodes, the connection may be used only by these two nodes. When the call is ended by one of the nodes, the connection is canceled.

There are several different types or categories of telephone systems that are found in businesses and organizations that can include a circuit-based network, and IP-based network, or both. Each type of telephone system has distinct advantages and disadvantages that should be considered when you plan and implement a telephony system.

• Centrex   Centrex is a type of telephone service that telephone companies lease to businesses and organizations. A traditional Centrex telephone system eliminates the need for a business or organization to purchase the telephony hardware that is used onsite to support the organization's telephone system. Typically, Centrex systems are used by small offices that rent Centrex services from a telephone company on a line-by-line and month-by-month basis. Centrex telephony systems are sometimes used by larger organizations, but are most frequently found in government, public, and private organizations. Centrex frequently uses analog telephone lines for the connections to a business or organization. However, it can also use T1-circuits with a demultiplexer onsite to support analog and digital telephones or ISDN lines.

  In a Centrex-based telephony system, the telephone company's central office acts as the telephone exchange. It is designed specifically to support the needs of a given organization. The central telephone office routes the calls that originate from inside the company to the appropriate internal or external telephone number. Centrex uses the telephone company’s central office exchange to route internal calls back to an extension. For example, with Centrex, the telephone exchange or telephone company's central office knows which extensions are internal. Therefore, an employee who is located within the organization's telephony network can dial another employee in the same telephony network or dial plan by using a 4-digit extension number. When a call is dialed to the internal telephone extension number, it is forwarded to the telephone company’s central office and then is routed back to the extension number that initiated the call.

A variation of a traditional Centrex telephony system is called IP Centrex. In an IP Centrex telephone system, the call is sent through an IP gateway that is located at a telephone company’s central office or located onsite at a service provider. In this kind of telephone system, the IP gateway translates the call into IP-based data packets that can be sent over the Internet or sent over a Voice over IP (VoIP)-based network. However, if the call is sent over the Internet, there is typically another IP gateway that receives the call and then translates the call back to a traditional circuit-switched call.

Organizations that currently have a traditional Centrex telephone system in place must install, deploy, and maintain one or more IP gateways for Exchange 2007 Unified Messaging to work correctly. Exchange 2007 Unified Messaging may require that you install, deploy, and maintain IP gateways to work with IP Centrex. There are several variables that will determine whether you must have an IP gateway. These variables include the type of telephones that are used in your organization (analog, digital, or IP) and the protocols that are supported by the IP Centrex system.

• Key telephone   In a Key telephone system, the telephone company’s central office is connected to the organization by using standard analog or digital telephone lines. A single telephone extension number is connected to multiple telephones so that when a call is placed into the organization by using this telephone number, all the telephones that are associated with that line or extension number will ring at the same time.

With Key telephone systems, individual users share lines across telephones. Therefore, callers will not experience frequent busy signals when they try to call into an organization. Key telephone systems are typically used by small offices where internal call volume is high but external call volume is low.

Key telephone systems have become more sophisticated over time and can work with Exchange 2007 Unified Messaging if an IP gateway is added. However, some less sophisticated systems may not work even if a supported IP gateway is used.

• PBX   A legacy PBX is a telephony device that switches calls in a telephony or circuit-switched network. A legacy PBX is a PBX that does not have a network adapter and cannot pass IP packets. Because they cannot pass IP packets, some businesses and organizations have replaced legacy PBXs with IP PBXs. For a list of PBXs that are supported by Exchange 2007 Unified Messaging, see the Telephony Advisor for Exchange Server 2007 Web site.

  PBXs are used by most medium- and larger-sized companies. A PBX enables users or subscribers of the PBX to share a certain number of outside lines for making telephone calls that are considered external to the PBX. A PBX is a much less expensive solution than giving each user in a business a dedicated external telephone line. Telephones, in addition to fax machines, modems, and many other communication devices, can be connected to a PBX.

  The PBX equipment is typically installed on an organization's premises and connects calls between the telephones located onsite and the telephone company. A limited number of outside lines, also known as trunk lines, are typically available for making and receiving calls that are external to the business from an external source such as the PSTN.

  To enable a legacy PBX to be used with Exchange 2007 Unified Messaging, you must deploy a supported IP gateway. For a list of supported IP gateways, see the Telephony Advisor for Exchange Server 2007 Web site.

• IP PBX   An IP PBX is a PBX that has a network adapter that supports the IP protocol. It is a piece of telephone switching equipment that generally resides in an organization or business instead of being located at a telephone company office. There are two types of IP PBXs: traditional IP PBXs and hybrid IP PBXs. Both traditional IP PBXs and hybrid IP PBXs support the IP protocol for sending voice conversations in packets to VoIP-based telephones. However, hybrid IP PBXs also connects traditional analog and digital telephones.

  IP PBXs are frequently easier to administer than legacy PBXs, because administrators can more easily configure IP PBX services by using an Internet browser or another IP-based tool. Also, no additional wiring, cabling, or patch panels must be installed. With an IP PBX, you can move an IP-based telephone by merely unplugging a telephone and plugging it in at a new location. This enables you to avoid the costly service calls that are required to move a telephone from legacy PBX vendors. Additionally, organizations that own an IP PBX do not have to incur the additional infrastructure costs that are required to maintain and manage separate circuit-switched and packet-switched networks. For a list of IP PBXs that are supported for Exchange 2007 Unified Messaging, see the Telephony Advisor for Exchange Server 2007 Web site.

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Legacy and Traditional PBX Configurations

On telephony networks that have legacy or traditional PBXs, a PBX does the following:

• Creates connections or circuits between the telephone sets of two users

• Maintains the connection as long as the users need the connection.

• Provides information for accounting purposes (for example, meters calls)

In addition to the three functions included in the previous list, PBXs may offer other calling features such as:

• Auto attendants

• Call accounting

• Call pick-up

• Call transfer

• Call waiting

• Conference calling

• Direct Inward Dialing (DID)

• Do Not Disturb (DND)

Although there are several manufacturers of PBXs, they all fit into two basic categories: analog and digital. These types of PBXs are frequently known as legacy or traditional PBXs.

Typically, PBX systems are connected to the telephone company’s central office by using special telephone lines, known as T1- and E1-lines. T1- and E1-lines have multiple channels. These telephone lines are also known as trunk lines. They enable the central office or the PBX to send multiple calls over the same line for better efficiency by using a simplified wiring layout. A PBX can also work with analog or ISDN lines.

You can control how many channels or lines you want to configure to receive calls that come from external callers and how many channels or lines to devote to calls that come from callers inside your organization by correctly configuring your PBX. Configuring the number of channels or lines helps prevent busy signals and enables you to configure the number of channels or lines that can be devoted to applications such as call centers. Correctly configuring your PBX is a cost effective method for managing the channels or lines in your organization because it reduces the number of leased lines that are needed.

A PBX can route a specific dialed telephone number to a specific telephone so that users can have their own individual telephone number or extension number. This is known as a Direct Inward Dialing (DID) number. When the telephone number is dialed for a user, the telephone company sends the DID number to the PBX by using Dialed Number Identification Service (DNIS). Because the telephone company uses DNIS to send the number, there is no need for operator intervention to route the call. The PBX has the information about the call to correctly route it to the number that was dialed by the caller. For a list of PBXs that are supported by Exchange 2007 Unified Messaging, see the Telephony Advisor for Exchange Server 2007 Web site.

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Analog and Digital PBXs

Analog PBXs send voice and call signaling information, such as the touch tones of a dialed telephone number, as an analog sound. Therefore, the sound is never digitized. To correctly direct the call, the PBX and the telephone company’s central office have to listen for the signaling information.

Note

Touchtone is more technically known as dual tone multi-frequency (DTMF). When a caller presses a key on a telephone keypad, the telephone produces two separate tones: a high frequency tone and a low frequency tone. When a person speaks into the telephone, only a single tone or frequency is emitted. Sending two tones with different frequencies at the same time reduces the possibility that the signaling tones will be interpreted as a human voice or that a human voice will be interpreted as the signaling tones.

Digital PBXs encode or digitize the analog sound into a digital format. Digital PBXs typically encode the voice sounds using a standard industry audio codec like G.711 or G.729. After the digitized voice is encoded, it is sent over a channel by using circuit switching. Circuit switching sets up an end-to-end open connection. It leaves the channel open for the length of the call and for the caller's exclusive use. However, the signaling method that is used by the PBX depends on the manufacturer. PBX manufacturers may have their own proprietary signaling method for call setup. For more information about the audio codecs that are used, see Understanding Unified Messaging Audio Codecs later in this white paper.

Note

Digital PBXs can support both digital and analog trunk lines.

In larger organizations, PBXs make it possible for employees in separate physical locations to contact one another by dialing an extension number for a user. This can be done by using a single PBX or may involve multiple PBXs that are networked together. PBXs at different office locations can be connected to a single transparent circuit-switched network by using T1- or E1-lines. When these lines connect PBXs together, they are frequently known as tie lines. The PBXs communicate with one another other across the tie lines by using a PBX-to-PBX protocol, such as QSIG. QSIG lets a set of PBXs act as if they are a single PBX.

This kind of PBX environment can also include advanced features, such as call transferring and telephone conferencing. In addition to allowing for advanced features, having two connected PBXs can also save the organization money because long distance charges between employees in the different locations will be reduced. This is because a call made between two employees remains on a tie line between the PBXs and requires that the user dial only an extension number for the other user instead of placing a long distance call.

The following figure illustrates a typical telephony and data network that includes legacy or traditional PBXs.

Legacy and traditional PBX configuration

In a telephony environment that includes a single or multiple analog or digital PBXs, an IP gateway is required between the PBX and the Exchange 2007 computer that has the Unified Messaging server role installed to convert the circuit-based protocols that are found on a telephony network into the IP-based protocols that are found on a data network. For more information about IP gateways, see the following topics:

• Supported IP Gateways

• IP PBX and PBX Support

• Managing IP Gateways

For a list of IP gateways that are supported for Exchange 2007 Unified Messaging, see the Telephony Advisor for Exchange Server 2007 Web site.

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IP PBX Configurations

An IP PBX is a PBX that supports the IP protocol to connect telephones by using an Ethernet or packet-switched LAN. It sends voice conversations in IP or data packets. An IP PBX may have multiple interfaces. These include interfaces for a data network and other interfaces that allow for a connection to a telephony or circuit-switched network.

The development of real-time Internet protocols has made it possible to successfully send voice and fax messages over a data network. Such real-time Internet protocols include the VoIP protocols that are used with Exchange 2007 Unified Messaging: Session Initiation Protocol (SIP) over Transmission Control Protocol (TCP) for voice messaging and T.38 for faxing. These protocols have made it possible to successfully send voice and fax messages over a data network. Real-time VoIP protocols are required to send voice messages over a packet-switched or data network so that the delivery order and timing of data packets can be maintained and controlled. If these protocols were not used to maintain and control the delivery and timing of the data packets, a person's voice would be broken up and would be sound incoherent or the images might appear garbled. For more information about VoIP protocols that are used in Exchange 2007 Unified Messaging, see Understanding Unified Messaging VoIP Security later in this white paper. For a list of IP PBXs that are supported for Exchange 2007 Unified Messaging, see the Telephony Advisor for Exchange Server 2007 Web site.

Note

Exchange 2007 Unified Messaging supports only SIP over TCP.

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Traditional IP PBX Configurations

A standard or traditional IP PBX contains at least a single network interface that connects to a data network by using VoIP protocols. It may also contain additional network interfaces or other telephony interfaces that enable it to connect to an existing telephony network such as the PSTN. The connection to the data network allows for communication with other VoIP hosts that are located on the data network by using IP data packets. These VoIP hosts include other IP PBXs, VoIP-based telephones, IP gateways, and Exchange 2007 Unified Messaging servers. A traditional IP PBX is does not support analog or digital telephones. It supports only VoIP telephones.

The following figure illustrates a typical telephony and data network that includes a traditional IP PBX.

IP PBX configuration

Because the IP PBX can already connect to a data network and can convert the circuit-based protocols from the PSTN to packet-switched VoIP protocols, an IP gateway may not be required to enable communication with Unified Messaging servers on the data network.

IP PBX Hybrid Configurations

Hybrid IP PBXs can provide analog, digital, and VoIP-based capabilities. If the correct interfaces are installed on an IP PBX and the software that supports multiple types of interfaces is installed correctly, the IP PBX is considered a hybrid IP PBX. An IP PBX hybrid makes it possible to use a mixture of analog, digital, and IP-based telephones.

Most modern IP PBXs can support and provide all three types of voice communication or a traditional IP PBX can be upgraded to a hybrid IP PBX by installing the necessary interfaces and software or firmware updates.

The mixture of analog, digital, and IP-based telephones makes it possible for users in your organization to use many new features and also provides great flexibility in your telephony environment. Using an IP PBX hybrid also allows for a more gradual migration to a completely VoIP-based telephony environment and voice messaging system for your organization.

The following figure illustrates a typical telephony and data network that includes an IP PBX hybrid configuration.

IP PBX hybrid configuration

There are several factors that determine whether an IP gateway will be required when you connect with an Exchange 2007 Unified Messaging server. One of these factors is the compatibility of the VoIP protocols that are used by the IP PBX or hybrid IP PBX and Exchange 2007 Unified Messaging. If an IP gateway is not required, it will reduce the complexity of the telephony infrastructure, and the support that you must have for Exchange 2007 Unified Messaging will be simpler.

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Calling or Called Party Identification

Calling or called party identification is a telephone company service that can tell the person who is receiving the call the telephone number and sometimes the name of the person who is calling and other information about the call. This information is sent over a serial cable by using call signaling. When a call is received by a PBX or IP PBX from a telephone company, the call includes calling identification information such as the following:

• The calling party's number

• The called party's number

• Status codes such as a ring-no-answer, the state or condition of the line, line busy, and call forward always (CFA)

• The line or port number that is being used for the call

Note

The call information, which is sent by using one of the signaling methods that is listed later in this section, is also used to enable Message Waiting Indicator (MWI) functionality. Exchange 2007 Unified Messaging does not include support for the Message Waiting Indicator (MWI) feature. However, you can obtain information about how to enable this feature by visiting the Geomant Web site. This third-party application extends Exchange 2007 Unified Messaging to include the Message Waiting Indicator (MWI) and Short Message Service text messaging capability.

Note

The third-party Web site information in this topic is provided to help you find the technical information you need. The URLs are subject to change without notice.

In telephony, the signaling information is used to exchange information between endpoints on a network to set up, control, and end calls. Several signaling methods that are used by IP gateways and IP PBXs are supported by Exchange 2007 Unified Messaging. The signaling method that is used depends on the type of device that is being used and the type of signaling method that is used by the telephone company. The most important factor is that the device that is connecting to the telephone company and to the IP gateway or IP PBX must support at least one of the signaling methods that enable calling or called party information to be sent and received by callers. For more information about signaling configuration information for a supported IP gateway, see the following:

• For AudioCodes IP gateways, see the Microsoft UM Specialist Resource Page.

• For Dialogic IP gateways, see the Certified Dialogic Media Gateways for Microsoft Exchange Server 2007 Unified Messaging.

  Note

  The third-party Web site information in this topic is provided to help you find the technical information you need. The URLs are subject to change without notice.

Although there are other signaling methods that can be used, the two most popular signaling methods are as follows:

• Simplified Message Desk Interface (SMDI)   SMDI is a protocol that is used to provide signaling, call control, and calling identification information from an interface between a telephone system and a voice mail system. It is used to provide the voice mail system with the information that it must have to process an incoming call. Every time that an incoming call is sent by using SMDI over a serial interface or RS-232 interface, the information that is sent will identify the line or port, the type of call, and the calling or called party numbers. The SMDI cable connects from a device such as a PBX to a serial connection on the IP gateway. However, SMDI is also used with IP PBXs. The SMDI protocol allows for a maximum of only 10 digits for each calling and called number. This is a limitation of the protocol and cannot be changed.

• In-band   In-band signaling allows for the exchange of signaling, call control, and calling identification information from a telephone company. This information is sent over the same channel and in the same band (300 Hz to 3.4 kHz) as the voice and other sounds that are being made during the call. For example, when a user places a call by using DTMF or touchtone dialing and talks to the called party, both the touchtone and the voice conversation use the same channel and band. In-band signaling is less secure because the control signals are exposed to the user and is a less popular signaling method than SMDI. In-band signaling applies only to Channel Associated Signaling (CAS).

  Important

  We recommend that all customers who plan to deploy Exchange 2007 Unified Messaging obtain the assistance of a Unified Messaging specialist. A Unified Messaging specialist will help make sure that there is a smooth transition to Exchange 2007 Unified Messaging from a legacy voice mail system. Performing a new deployment or upgrading a legacy voice mail system requires significant PBX and Exchange 2007 Unified Messaging knowledge. For more information about how to contact a Unified Messaging specialist, see the Microsoft Exchange Server 2007 Unified Messaging (UM) Specialists Web site.

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Overview of Unified Messaging Components

The Microsoft Exchange Server 2007 Unified Messaging (UM) server role introduces new concepts in Exchange messaging. Exchange 2007 Unified Messaging provides a single storage location for e-mail, voice mail, and fax messages.

This topic provides an overview of the new components, features, and concepts in Exchange 2007 Unified Messaging, including the following:

• Active Directory Unified Messaging objects

• Auto attendants

• Subscriber access by using Outlook Voice Access

Active Directory Unified Messaging Objects

After you install and configure the Unified Messaging server role on a computer that is running Exchange 2007, you create Active Directory objects that enable the Unified Messaging functionality that is found in Exchange 2007. You must create the following objects after you successfully install the Unified Messaging server role:

• Dial Plan objects

• IP Gateway objects

• Hunt Group objects

• Mailbox Policy objects

• Auto Attendant objects

• Unified Messaging Server objects

The Active Directory UM objects provide the configuration information that is required to integrate Exchange 2007 Unified Messaging, Active Directory, and the existing telephony infrastructure. Each type of object that is created in Active Directory controls a feature set in Exchange 2007 Unified Messaging.

For example, when you create a UM Auto Attendant object, the settings on the Auto Attendant object control the features and settings for that auto attendant. When you configure or modify an Auto Attendant object, you control such settings as business hours, non-business hours, informational greetings, and whether to use dual tone multi-frequency (DTMF) inputs or to enable speech recognition for the auto attendant.

For more information about Unified Messaging objects, see Overview of Unified Messaging Active Directory Objects later in this white paper.

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Auto Attendants

When internal or external callers call in to the Exchange 2007 Unified Messaging system, a series of voice prompts assists them in moving through the menu system called an auto attendant. The auto attendant enables the caller to connect to a person in an organization or locate a user in the organization so that they can place a call without assistance from a human operator. Callers hear voice prompts instead of a human operator, such as, "Press 1 for technical support."

You can create multiple auto attendants in Exchange 2007 Unified Messaging. Within Active Directory, each auto attendant is represented as an object. Configuration settings for an auto attendant are made on the Active Directory object and can include language settings, customized menus, and other menu navigational settings. You can also configure each UM auto attendant so that when an external caller or an internal caller places a call, and it is answered by a UM auto attendant, the caller can use either DTMF inputs or voice inputs to move through the Unified Messaging menu system.

Note

When a caller uses the keypad on a telephone to move through the menu system, it is called DTMF input. If this is the case, the telephone user interface (TUI) is used.

For more information about auto attendants, see Understanding Unified Messaging Auto Attendants later in this white paper.

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Subscriber Access

Exchange 2007 Unified Messaging gives subscribers access to the Unified Messaging system. A subscriber is an internal business user or network user who has been enabled for Unified Messaging and has an Exchange 2007 mailbox. Subscriber access is used by the internal users to access their individual mailboxes to retrieve e-mail, voice messages, and contact and calendar information. Each Dial Plan object that is created contains at least one subscriber access number or extension number. Subscribers use this telephone or extension number to access their individual mailboxes.

For more information about subscriber access, see Understanding Unified Messaging Subscriber Access later in this white paper.

There are two Exchange 2007 Unified Messaging user interfaces available to UM-enabled subscribers: the telephone user interface (TUI) and the voice user interface (VUI). In Exchange 2007, these two interfaces together are called Outlook Voice Access. A subscriber can use Outlook Voice Access when they access the Unified Messaging system from an external or internal telephone. They can use Outlook Voice Access to access their Exchange 2007 mailbox, including their personal e-mail, voice messages, and calendar information.

Note

For a copy of the Microsoft Exchange 2007 Unified Messaging Outlook Voice Access Quick Reference Guide, visit the Microsoft Download Center.

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Understanding Unified Messaging Incoming Call Handling

This topic provides an overview of the call handling features that are included with Microsoft Exchange Server 2007 Unified Messaging (UM). Each section in this topic gives you the information that is required to understand one or more of the call handling features that are included in Exchange 2007 Unified Messaging.

Overview of Unified Messaging Incoming Call Handling

Call handling is a term that is used to describe how incoming calls are answered and handled by a computer that is running Exchange 2007 Unified Messaging. The types of incoming calls that are handled by Exchange 2007 UM include the following:

• Voice calls

• Fax calls

• Outlook Voice Access

• The Play on Phone feature

• UM auto attendants

For more information about Unified Messaging message flow and routing, see Overview of the Unified Messaging Call Processing later in this white paper.

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Voice Calls

Voice call handling is used when an internal or external user leaves a voice message for a subscriber on the Exchange 2007 Unified Messaging system. Incoming voice calls are created as MIME messages and then submitted by using Simple Mail Transfer Protocol (SMTP) from the Exchange 2007 computer that has the Unified Messaging server role installed to an Exchange 2007 computer that has the Hub Transport server role installed. The two server roles must be installed in the same Active Directory site. The SMTP message transport for incoming voice calls is not only site aware, but all voice messages are submitted to the Hub Transport server by using SMTP, even if the mailbox resides on the same computer that has the Mailbox server role installed.

For more information about voice calls and message routing, see Unified Messaging Voice and Fax Call Processing later in this white paper.

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Fax Calls

Fax call handling is used when an internal or external user sends a fax message to a UM-enabled recipient on the Exchange 2007 Unified Messaging system. Incoming fax calls are created as MIME messages and are submitted from the Unified Messaging server to a Hub Transport server in the same Active Directory site by using SMTP. The SMTP message transport for incoming fax calls is not only site aware, but all fax messages are submitted to the Hub Transport server by using SMTP, even if the mailbox resides on the same Mailbox server.

For more information about fax calls and message routing, see Unified Messaging Voice and Fax Call Processing later in this white paper.

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Outlook Voice Access

Unified Messaging servers also process and route incoming calls that are received by Outlook Voice Access users. When a UM-enabled user or subscriber dials a subscriber access number that is set on a UM dial plan to access their Exchange 2007 mailbox, they are presented with a welcome message and a series of telephone user interface (TUI) voice prompts. The voice menu system that is presented to the user is called Outlook Voice Access. These voice prompts help the user to navigate and interact with the Unified Messaging system by using touchtone or speech inputs.

Note

When an Outlook Voice Access caller uses touchtone inputs on a telephone keypad, the TUI is used. When the same caller uses speech inputs over the telephone, the voice user interface (VUI) is used.

For more information about the TUI voice prompts found in Exchange 2007 Unified Messaging, see Understanding Unified Messaging Audio Prompts later in this white paper.

Outlook Voice Access is the feature that enables a UM-enabled user to access their Exchange 2007 mailbox by using an analog, digital, or cellular telephone. By accessing their Exchange 2007 mailbox they can perform the following tasks:

• Listen to new and saved e-mail and voice mail messages.

• Forward, reply, save, and delete e-mail and voice messages.

• Interact with their calendar, including:

  • Listening to daily calendar appointments and meeting details.

  • Accepting or declining e-mail and meeting requests.

  • Sending an "I'll be late" message to meeting participants.

  • Replying to a meeting request by using voice inputs to send a message to meeting participants.

  • Declining or canceling meetings.

• Interact with global address list (GAL) and personal contacts. These interactions may include:

  • Locating a person in the GAL or personal contacts.

  • Inputting a telephone extension number to leave a message for a person.

  • Sending a voice message to a person.

• Change their PIN, spoken name, or greetings.

For more information about how to navigate the Outlook Voice Access menus, see the Microsoft Exchange Server 2007 Unified Messaging Outlook Voice Access Quick Start Guide. This guide is available in the <Program Files>\Microsoft\Exchange Server\bin folder.

For more information about Outlook Voice Access message routing, see Unified Messaging Outlook Voice Access Call Processing later in this white paper.

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The Play on Phone Feature

To enable the Play on Phone feature for UM-enabled users, the UM server must first answer and then correctly route a call when it is placed by a user who is using Exchange 2007 Outlook Web Access or Microsoft Office Outlook 2007. If a UM-enabled user is in a location that is not private or the voice message is confidential, they will likely not want to play their voice message over their computer speakers. The Exchange 2007 Unified Messaging Play on Phone feature lets a UM-enabled user listen to a voice message by using a telephone instead of playing it over their computer speakers or headphones.

For more information about Play on Phone message flow see, Unified Messaging Play on Phone Call Processing later in this white paper.

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UM Auto Attendants

To enable the UM auto attendant feature found in Exchange 2007 Unified Messaging, UM servers must correctly answer and then route the incoming calls that are received from internal and external anonymous or unauthenticated users.

To enable a UM auto attendant to answer incoming calls, you must first enable and configure a UM auto attendant. Creating and configuring UM auto attendants is an optional feature in Exchange 2007 Unified Messaging. However, auto attendants help internal and external callers locate and place calls to company users or departments that are in an organization.

A UM auto attendant is a set of voice prompts that callers hear instead of a human operator when they place a call to an organization that has Exchange 2007 Unified Messaging. A UM auto attendant helps callers navigate the organization's menu system by using dual tone multi-frequency (DTMF) (also known as touchtone) inputs or voice-activated inputs that use Speech Recognition so that they can locate a user or caller in an organization and then place a call to that user or department.

• For more information about UM auto attendant message routing, see Unified Messaging Auto Attendant Call Processing later in this white paper.

• For more information about UM auto attendants, see Understanding Unified Messaging Auto Attendants later in this white paper.

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Understanding Unified Messaging Subscriber Access

When you are deploying Microsoft Exchange Server 2007 Unified Messaging, you must understand subscriber access and the new features that are included with Exchange 2007 that depend on subscriber access. This topic describes subscriber access and how it is used in Exchange 2007 Unified Messaging to let subscribers, also known as UM-enabled users, access their Exchange 2007 mailbox.

Subscriber Access

A subscriber is an internal business user or network user who is enabled for Exchange 2007 Unified Messaging. Subscriber access is used by users to access their individual mailboxes to retrieve e-mail, voice messages, contacts, and calendaring information. Outlook Voice Access is the new Exchange 2007 Unified Messaging feature that lets subscribers access their Exchange 2007 mailbox.

When you enable subscriber access for Exchange 2007 UM-enabled users, you must install the Exchange 2007 Unified Messaging server role on the computer that is running Exchange 2007 and verify that at least one of each of the following have been created:

• UM dial plan

• UM mailbox policy

• UM IP gateway

• UM hunt group

  Note

  If you want to prevent a user from receiving voice mail but want to allow them access to their Exchange 2007 mailbox by using Outlook Voice Access, you can enable the user for Unified Messaging and configure the user's mailbox with an extension number that is currently not being used by another user in the organization.

• When you configure subscriber access, you configure the UM dial plan to have a subscriber access number. The telephone number or number that is configured on the UM dial plan is the telephone number that subscribers will use to access their Exchange 2007 mailboxes over the telephone by using Outlook Voice Access. The subscriber access feature included with Exchange 2007 Unified Messaging resembles other unified messaging solutions. However, Exchange 2007 offers more advanced features than other unified messaging solutions. For more information about how to create or modify UM dial plans and enable subscriber access, see How to Create a New Unified Messaging Dial Plan.

Note

A UM dial plan must contain at least one subscriber access number, but can contain multiple subscriber access numbers.

For more information about how to enable a user for Unified Messaging, see How to Enable a User for Unified Messaging.

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Outlook Voice Access

There are two Exchange 2007 Unified Messaging user interfaces available to subscribers: the Telephone User Interface (TUI) and the Voice User Interface (VUI). In Exchange 2007 these two interfaces together are called Outlook Voice Access. Outlook Voice Access can be used when a subscriber accesses the Unified Messaging system from an external or internal telephone to access their individual mailbox, including their personal e-mail, voice messages, contacts, and calendaring information in their Exchange 2007 mailbox.

Note

For a copy of the Microsoft Exchange 2007 Unified Messaging Outlook Voice Access Quick Start Guide, see the Microsoft Download Center.

The following scenarios demonstrate how Outlook Voice Access can be used for subscriber access:

• From a telephone: An Outlook Voice Access user places a call to the subscriber access number from a telephone and wants to access their voice mail. The voice prompt says, "Welcome. You are connected to Microsoft Exchange. To access your mailbox, please enter your extension. To contact someone, press the # key." After the user enters their mailbox extension number, the voice prompt will say, "Please enter your PIN and press the # key." After the user enters their PIN, the voice prompt says, "You have 2 new voice mails, 10 new e-mail messages, and your next meeting is at 10:00 A.M. Please say voice mail, e-mail, calendar, personal contacts, directory, or personal options." When the user says "E-mail", UM reads the message header and then the name, subject, time, and priority for the messages that are in the subscriber's mailbox.

• From a telephone: An Outlook Voice Access user places a call to the subscriber access number from a telephone and wants to access their voice mail. The voice prompt says, "Welcome. You are connected to Microsoft Exchange. To access your mailbox, please enter your extension. To contact someone, press the # key." After the user enters their mailbox extension, the voice prompt will say, "Please enter your PIN and press the # key." After the user enters their PIN, the voice prompt says, "You have 2 new voice mails, 10 new e-mail messages, and your next meeting is at 10:00 A.M. Please say voice mail, e-mail, calendar, personal contacts, directory, or personal options." When the user says "Calendar", UM says, "Sure, and which day should I open?" The user says, "Today's calendar." UM responds by saying, "Opening today's calendar." UM reads each of the calendar appointments for that day for the user.

  Note

  If a Unified Messaging server encounters a corrupt calendar item in a user's mailbox, it will fail to read the item, but will return the caller to the Outlook Voice Access main menu and will skip reading any additional meetings that may be scheduled for the rest of the day.

• From a telephone: An Outlook Voice Access user places a call to the subscriber access number from a telephone and wants to access their voice mail. The voice prompt says, "Welcome. You are connected to Microsoft Exchange. To access your mailbox, please enter your extension. To contact someone, press the # key." After the user enters their mailbox extension number, the voice prompt will say, "Please enter your PIN and press the # key." After the user enters their PIN, the voice prompt says, "You have 2 new voice mails, 10 new e-mail messages, and your next meeting is at 10:00 A.M. Please say voice mail, e-mail, calendar, personal contacts, directory, or personal options." The user says "Voice mail" and UM reads the message header and then the name, subject, time, and priority for the voice messages that are in the user's mailbox.

  Important

  For the VUI or Automatic Speech Recognition (ASR) to be used for subscriber access, it must be enabled on the UM dial plan to enable the VUI functionality as described in the earlier scenarios.

  Note

  If speech recognition is enabled, users can access their UM-enabled mailbox by using speech input. However, subscribers can also use touchtone, also known as dual tone multi-frequency (DTMF), by pressing 0. Speech recognition is not enabled for PIN input.

• From a telephone: An Outlook Voice Access user places a call to the subscriber access number from a telephone and wants to locate a person in the directory by spelling their e-mail alias. The voice prompt says, "Welcome. You are connected to Microsoft Exchange. To contact someone, press the # key." The user presses the # key, and then spells the name of the person they want to contact by using DTMF or touchtone inputs.

  Note

  The directory search feature with subscriber access is not speech-enabled. Users will be able to spell the name of the person who they want to contact only by using DTMF inputs.

  Important

  In some companies (especially in East Asia), office telephones may not have letters on the keys of the telephone. This makes the spell-the-name feature that uses the DTMF interface almost impossible without a working knowledge of the key mappings. By default, Exchange 2007 Unified Messaging uses the E.161 key mapping. For example, 2=ABC, 3=DEF, 4=GHI, 5=JKL, 6=MNO, 7=PQRS, 8=TUV, 9=WXYZ.
  When inputting the combination of letters and numbers, for example "Mike1092", the numeric digits are mapped to themselves. For an e-mail alias of "Mike1092" to be entered correctly, the user will have to press the numbers 64531092. Also, for characters other than A-Z and 0-9, there will not be a telephone key equivalent. Therefore, these characters should not be entered. For example, the e-mail alias "mike.wilson" would be entered as 6453945766. Even though there are 11 characters to be input, only 10 digits are entered by the user because the period (.) does not have a digit equivalent.

Important

If you delete the last message in your inbox by using Outlook Voice Access, you will be unable to undelete the message. If you need to access the e-mail message after you have deleted it by using Outlook Voice Access, you can use Outlook Web Access or Outlook to move the e-mail message back into the appropriate folder from the deleted items folder. You cannot use Outlook Voice Access to access the deleted items folder.

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Understanding Unified Messaging Audio Prompts

When you install the Unified Messaging server role on a computer that is running Microsoft Exchange Server 2007, a common set of default audio files that are used for Unified Messaging system and menu prompts, greetings, and informational announcements are copied to the computer that is running the Unified Messaging server role. Although you can have a fully functional UM auto attendant or a dial plan that uses only the default audio prompts that are included inExchange 2007, the audio files that are installed for greetings, informational announcements, and system and menu prompts are too generic to serve as an acceptable public interface for many companies. This topic discusses the system and menu prompts, greetings, and informational announcements that are used by UM dial plans and auto attendants and how they are used when callers access the Unified Messaging system.

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Overview of Audio Prompts and Greetings

After the Unified Messaging server role has been installed, audio files for UM dial plans and auto attendants are copied to the UM server. By default, the installation program copies the audio files to the Program Files\Microsoft\Exchange Server\Unified Messaging\Prompts\<language> folder. If you have installed the U.S. English version of Exchange 2007, a folder named \en is created during installation to hold the U.S. English versions of the system prompts. These system prompts are played to callers by the UM server to enable them to hear greetings, menu prompts, and informational announcements and to enable callers to navigate the Unified Messaging menus.

These system audio files or prompts that are copied to the UM server should never be changed. However, Unified Messaging does enable you to customize UM dial plan and auto attendant welcome greetings, main menu prompts, and informational announcements.

The following table summarizes the prompts and greetings that are used with UM dial plans.

Audio prompts for UM dial plans

Prompts and greetings	Description
System prompts	Must not be modified.
Welcome greeting	The default welcome greeting is a system prompt that is played by default. However, you can use a customized greeting file that you create.
Informational announcement	By default, informational announcements are disabled. If you enable an informational announcement, you must specify a customized greeting file.

The following table summarizes the prompts and greetings that are used with UM auto attendants.

Audio prompts for UM auto attendants

Prompts and greetings	Description
System prompts	Must not be modified.
Business hours menu prompts	By default, business hours menu prompts are enabled and a system prompt is played. However, you can use a customized greeting file that you create.
Non-business hours menu prompts	By default, non-business hours prompts are enabled and a system prompt is played. However, you can use a customized greeting file that you create.
Business hours greeting	By default, a business hours greeting is enabled and a system prompt is played. However, you can use a customized greeting file that you create. This is also known as a welcome greeting.
Non-business hours greeting	By default, a non-business hours greeting is enabled and a system prompt is played. However, you can use a customized greeting file that you create. This is also known as a welcome greeting.
Informational announcement	By default, informational announcements are disabled. If you enable an informational announcement, you must specify a customized greeting file.

Warning

Modifying the system prompts that are installed is not a supported configuration.

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System Prompts

Exchange 2007 Unified Messaging (UM) is installed with a set of default audio prompts for use with Outlook Voice Access, dial plans, and auto attendants. There are hundreds of system prompts for each language that are installed on the computer that is running the Unified Messaging server role. The UM server plays the audio files for these system prompts to callers when they access the Unified Messaging system. Examples of these system prompts include the following:

• "Please enter your PIN."

• "To access your mailbox, enter your extension."

• "To contact someone, press the # key."

• "Spell the name of the person you are calling, last name first."

• "To reach a specific person, just tell me their name."

  Warning

  Modifying the system prompts that are installed is not a supported configuration.

  Note

  When the Microsoft Exchange Unified Messaging service starts on the computer that is running the Unified Messaging server role, it will verify that all the system prompts are available. If a system prompt cannot be found, it will return an error. To fix the error that is returned, locate the event by using Event Viewer and copy the file that is listed in the Event Properties window from the Exchange 2007 installation DVD into the appropriate folder on the UM server.

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UM Dial Plan Greetings and Announcements

After you install the Unified Messaging server role and create a UM dial plan, you have the option to use the audio files for the default system prompts that are copied to the UM server during installation or to create customized audio files that can be used with UM dial plans.

UM dial plans have a welcome greeting and an optional informational announcement that you can modify. The welcome greeting is used when Outlook Voice Access users or another caller calls the subscriber access number. The callers hear a default welcome greeting that says, "Welcome, you are connected to Microsoft Exchange." This audio file is the default greeting for a UM dial plan. However, you might want to change this greeting and provide an alternative welcome greeting that is specific to your company, such as, "Welcome to Outlook Voice Access for Woodgrove Bank." If you customize this greeting, you record the customized greeting and save it as a .wav file, and then you configure the dial plan to use this customized greeting.

UM allows for an informational announcement to follow the welcome greeting. By default, there is no informational announcement configured. However, you may want to provide one for callers. You can use the informational announcement for general announcements that change more frequently than the welcome greeting or for announcements that are required by corporate compliance policies. When it is important that the whole informational announcement is heard, you can configure it to be uninterruptible. This prevents a caller from pressing a key or speaking a command to interrupt and stop the informational announcement.

The following table describes the UM dial plan greetings and informational announcements.

UM dial plan greetings and informational announcements

Greeting	Default example	Customized example
Welcome greeting	"Welcome, you are connected to Microsoft Exchange."	"Welcome to Outlook Voice Access for Woodgrove Bank."
Informational announcement	By default, an informational announcement is not configured.	"By using this system you agree to adhere to all corporate policies when you are accessing this system."

When you are customizing and configuring greetings and announcements, make sure that the language setting that is configured on the UM dial plan is that same as the language of the custom prompts that you create. If not, a caller may hear one message or greeting in one language and another message or greeting in a different language.

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UM Auto Attendant Greetings, Announcements, and Menu Prompts

Like with UM dial plans, UM auto attendants have a welcome greeting, an optional informational announcement, and an optional custom menu prompt. There are different versions of the welcome greeting and menu prompt that you can configure for business hours and non-business hours. You can modify all of them.

The welcome greeting is the first thing that a caller hears when a UM auto attendant answers their call. By default, this says, "Welcome to the Microsoft Exchange auto attendant." The audio file that is played for the call is the default system prompt for the UM auto attendant. However, you may want to provide an alternative greeting that is specific to your company, such as, "Thank you for calling Woodgrove Bank." To customize this welcome greeting, record the customized greeting and save it as a .wav file, and then configure the auto attendant to use this customized greeting. As with the welcome greetings, you can also customize the menu prompts.

UM also allows for an informational announcement to follow a business hours greeting or a non-business hour greeting. By default, no informational announcement is configured, but you may want to provide one to callers. The informational announcement can announce your company's business hours, for example, "Our business hours are 8:00 A.M. to 5:00 P.M., Monday through Friday, and 8:30 A.M. to 1:00 P.M. on Saturday." The informational announcement can also provide information that is required for compliance with corporate policies, for example, "Calls may be monitored for training purposes." When it is important that the whole informational announcement is heard, you can configure it to be uninterruptible. This prevents the caller from pressing a key or speaking a command to interrupt and stop the informational announcement.

The following table describes the UM auto attendant greetings and informational announcements.

UM auto attendant greetings, informational announcement and menu prompts

Greeting	Default example	Customized example
Business hours greeting	"Welcome to the Exchange auto attendant."	"Thank you for calling Woodgrove Bank."
Non-business hours greeting	No default non-business hours greeting is played until you configure the business hours for the auto attendant. However, the business hours greeting is played for callers during all times of the day.	"You have reached Woodgrove Bank after business hours. Our business hours are from 8:00 A.M. until 5:00 P.M., Monday through Friday."
Informational announcement	By default, informational announcements are not configured.	"Calls may be monitored for training purposes."
Business hours main menu prompt	No default business hours main menu prompt will be played until you configure key mappings on the auto attendant.	"For technical support, press or say 1. For corporate offices and administration, press or say 2. For sales, press or say 3."
Non-business hours main menu prompt	No default non-business hours main menu prompt will be played until you configure key mappings and the business hours schedule on the auto attendant.	"Your call is very important to us. However, you have reached Woodgrove Bank after business hours. If you want to leave a message, please press or say 1, and we will return your call as soon as possible."

Like with UM dial plans, make sure that the language setting that is configured on the UM auto attendant is the same as the language of the custom greetings that you create and is set to the same language as the UM dial plan. If not, a caller may hear one message or greeting in one language and another message or greeting in a different language.

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Customizing Greetings, Announcements, and Menu Prompts

Although the system prompts must not be replaced or changed, you will probably want to customize the greetings, informational announcements, and menu prompts that are used with UM dial plans and auto attendants. After the Unified Messaging server role is installed, you can configure the UM dial plans and auto attendants to use these custom audio files (.wav). You must perform the following steps before you can enable custom voice prompts for callers:

• Record the custom greeting and save it as a .wav file. The Linear PCM (16 bit/sample), 8 kilohertz (kHz) audio codec must be used to encode the .wav file.

• Copy the customized greeting to the correct folder on a UM server by using the Copy-UMCustomPrompt Exchange Management Shell cmdlet or configure a custom greeting or prompt by using the Exchange Management Console.

• Configure the UM dial plan or auto attendant to use the customized greeting.

After you create the audio file for the custom prompt, announcement, or greeting you must use the Copy-UMCustomPrompt Exchange Management Shell cmdlet to copy the audio file to the UM prompt publishing point. The prompt publishing point is a property that is configured on a UM dial plan and is a shared folder structure that is created on the first UM server that is installed. The prompt publishing point distributes UM custom prompts to other UM servers in the Exchange 2007 organization. The Copy-UMCustomPrompt cmdlet supports the use of UM custom audio prompts by copying the specified audio file to the correct location for distribution to other UM servers in the Exchange 2007 organization.

Unified Messaging servers access the UM server prompt publishing point and copy the necessary .wav audio files to their local installation folder. After the file has been copied locally to the UM server, the UM server can provide the audio for a given custom prompt. For more information about custom prompt publishing, see Understanding Custom Prompt Distribution later in this white paper.

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Understanding Unified Messaging Audio Codecs

In Microsoft Exchange Server 2007 Unified Messaging (UM), a codec is used to store voice mail messages. Another codec is used between an IP gateway or IP Private Branch eXchange (PBX) and a server that is running Exchange 2007 that has the Unified Messaging server role installed. Exchange 2007 Unified Messaging can use any of the following three audio codecs to create and store voice messages:

• Windows Media Audio (WMA)

• Group System Mobile (GSM) 06.10

• G.711 Pulse Code Modulation (PCM) Linear

However, the G.711 (PCMA and PCMU) and the G.723.1 codecs are VoIP codecs are used between an IP gateway and the Unified Messaging server.

Part of planning your Unified Messaging system involves selecting the correct audio codec based on the needs and requirements of your organization. This topic discusses the audio codecs that Exchange 2007 Unified Messaging can use and will help you plan your UM deployment.

Important

On 64-bit Unified Messaging servers, you must install the Windows Media Encoder if you plan to use the WMA UM dial plan codec. For more information about how to install the Windows Media Encoder, see Availability of the Windows Media Audio 9 Voice codec for x64-based computers or visit the Microsoft Download Center.

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Codecs

Two types of codecs are used in Exchange 2007 Unified Messaging: the codec that is used between IP gateways and the Unified Messaging server or between a PBX and IP gateway, depending on the type of PBX, and the codec that is used to encode and store voice messages for users.

The term "codec" is a combination of the words "coding" and "decoding" and is used with digital audio data. A codec is a software program that transforms digital data into an audio file format or audio streaming format. Codecs are used to convert an analog voice signal to a digital version of the voice signal. Codecs can vary in their sound quality, the bandwidth that is required to use them, and the system requirements that are needed to do the encoding.

When you use an ordinary telephone over the Public Switched Telephone Network (PSTN) your voice is transported in an analog format over the telephone line. But with Voice over IP (VoIP), your voice must be converted into digital signals. This conversion process is known as encoding. Encoding is performed by a codec. After the digitized voice has reached its destination, it must then be decoded back to its original analog format so that the person on the other end of the call can hear and understand the caller.

VoIP Codec

In Exchange 2007 Unified Messaging, three types of codecs can be used between IP gateways and the Unified Messaging server or between a PBX and IP gateway, depending on the type of PBX. Unified Messaging servers can accept the following VoIP codecs from an IP gateway or IP PBX:

• G.711 µ-law

• G.711 A-law

• G.723.1

G.711 is a standard that was developed for use with audio codecs. There are two main algorithms defined in the standard for G.711.The µ-law algorithm that is used in North America and Japan and the A-law algorithm that is used in Europe and other countries. The G.723.1 audio codec is mostly used in VoIP applications and requires a license to be used. G.723.1 is a high quality, high compression type of codec.

Both a Unified Messaging server and a supported IP gateway or IP PBX can offer both the G.711 and G.723.1 codec. However, the Unified Messaging server will choose its preferred codec based on the WireCodecList subkey in the registry. By default, the first codec to be used is G.723.1.

If you want to use a different codec between the Unified Messaging server and the IP gateway or IP PBX, you change the configuration on the IP gateway or IP PBX and do not change the values for the WireCodecList subkey in the registry. The Unified Messaging server will determine the codec that is being used by the IP gateway or IP PBX and select the appropriate codec from the list in the registry.

The following table summarizes some common VoIP codecs.

VoIP codecs

VoIP codec	Bandwidth (Kbps)	Description
G.711	64	This codec requires very low processing. It needs a minimum of 128 kilobits per second (Kbps) for two-way communication.
G.723.1	5.3/6.3	This codec offers high compression with high quality audio. It requires more processing than the G.711 codec. The G.723.1 codec uses reduced bandwidth but offers poorer quality audio.

UM Voice Message Storage Codec

Unified Messaging dial plans are integral to the operation of Exchange 2007 Unified Messaging. By default, when you create a UM dial plan, the UM dial plan uses the WMA audio codec. However, after you create the UM dial plan, you can configure the UM dial plan to use GSM 06.10 or G.711 PCM Linear audio codecs.

Each audio codec has advantages and disadvantages. The WMA audio codec was selected as the default audio codec because of its sound quality and compression properties. GSM 06.10 and G.711 PCM Linear audio codecs were included as available options because of their ability to support other types of messaging systems.

When you plan for Exchange 2007 Unified Messaging, you must balance the size and the relative quality of the audio file that will be created for voice messages. Generally, the higher the bit rate for an audio file, the higher the quality. However, you must also consider whether the audio file is compressed. The sample bit rate (bit/sec) and compression properties for each audio codec that is used in Exchange 2007 Unified Messaging are as follows:

UM voice message storage codecs

Voice message storage codec	Bits	Compressed file?
WMA	16 bit	Yes
G.711 PCM	16 bit	No
GSM 06.10	8-bit	Yes

In Exchange 2007 Unified Messaging, the WMA, G.711 PCM Linear, and GSM 06.10 audio codecs are used to create .wma and .wav audio files for voice messages. However, the file type that is created depends on the audio codec that is used to create the voice message audio file. In Exchange 2007 Unified Messaging, the .wma audio codec creates .wma audio files and the GSM 06.10 and G.711 PCM Linear audio codecs produce .wav audio files. Both kinds of audio files are sent together with the e-mail message to the recipient of the voice message.

Frequently, but not always, coding and decoding the digital data also involves compression or decompression. Audio compression is a form of data compression that reduces the size of audio data files. The audio compression algorithm that is used by the audio codec compresses the .wma or .wav audio files. In Exchange 2007 Unified Messaging, the type of audio compression algorithm that is used is based on the type of audio codec that is selected in the UM dial plan properties. After the audio file is created and compressed, it is attached to the voice message.

Sometimes information from the digital data is lost during compression and decompression. The higher the compression that is used to compress the audio file, the greater the loss of information during the conversion. However, less disk space is used because size of the audio file is reduced. Conversely, the lower the compression, the lower the loss of the information. However, more disk space must be used because of the increased size of each audio file.

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UM Message Sizing

You can configure UM to use one of the three following audio codecs for creating voice messages: WMA, GSM 06.10, and G.711 PCM Linear. The WMA audio codec is always stored in the Windows Media format and the attachment is a file that has a .wma file name extension. Audio files encoded by using the GSM or G.711 PCM Linear audio codecs are always stored in RIFF/WAV format, and the attachment is a file that has a .wav file name extension.

The size of Unified Messaging voice messages depends on the size of the attachment that holds the voice data. In turn, the size of the attachment depends on the following factors:

• The duration of the voice mail recording

• The audio codec that is used

• The audio file storage format

The following figure illustrates how the size of the audio file depends on the duration of the voice mail recording for the three audio codecs that you can use in UM.

Note

In this figure, the average length of a call-answered voice message is approximately 30 seconds.

Audio file size

WMA

WMA is the most highly compressed audio codec of the three kinds of codecs. The compression is approximately 11,000 bytes for each 10 seconds of audio. However, the .wma file format has a much larger header section than the .wav file format. The .wma file header section is approximately 7 kilobytes (KB), whereas the header section for the .wav file is less than 100 bytes. Although WMA audio recordings are recorded for longer than 15 seconds, they become smaller than GSM audio recordings. Therefore, for the smallest, yet highest quality audio files, use the WMA audio codec.

G.711 PCM Linear

The G.711 PCM Linear audio codec creates .wav audio files that are not compressed. Therefore, G.711 PCM Linear .wav audio files occupy the most space for any given duration when they are compared to the GSM and WMA audio codecs. G.711 PCM Linear .wav audio files occupy just over 160,000 bytes for each 10 seconds of audio. G.711 PCM Linear .wav audio files have the highest audio quality of the three audio codecs that are used by Exchange 2007 Unified Messaging. However, the quality of comparable audio files that are created by using the WMA and GSM audio codecs are acceptable to most users who listen to voice messages.

GSM

The GSM audio codec creates .wav audio files that are compressed. GSM .wav audio files are just over 16,000 bytes for each 10 seconds of audio. However, GSM creates an audio file that is larger than the audio file that is created by the WMA audio codec. Therefore, when you are balancing the quality of the voice message and the size, this may not be the best choice.

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Understanding Custom Prompt Distribution

In Microsoft Exchange Server 2007 Unified Messaging (UM) you can create and configure UM dial plans or auto attendants that are fully functional but that use only the default audio prompts that are included in Exchange 2007. However, the audio files that are installed for greetings, informational announcements, and menu prompts are generic and should be customized and then distributed to all the Unified Messaging servers in your organization. This topic explains how a custom prompt is copied to all computers that have the Unified Messaging server role installed. This ensures that the custom audio prompts will be available to all callers who use Outlook Voice Access and UM auto attendants.

Overview of Custom Prompt Distribution

Custom prompt publishing is the process by which custom audio files are made available to all Outlook Voice Access users and callers who dial in to UM auto attendants. After you have created a custom audio prompt, you must first copy the custom prompt to the Unified Messaging server that you have designated as the prompt publishing point. The prompt publishing point is a shared folder that is located on the first server to be associated with a single UM dial plan. After the custom audio file is copied to the prompt publishing point, all the Unified Messaging servers that are members of the same dial plan will copy the custom audio prompt to a local folder. By copying the custom audio file to a local folder, the Unified Messaging server or servers will be able to play the custom file for Outlook Voice Access users or when callers dial in to a UM auto attendant.

The UM custom prompts that exist in the prompt publishing point will be copied locally by a Unified Messaging server regardless of the number of Unified Messaging servers that belong to the UM dial plan. Each UM dial plan represents a set of Unified Messaging servers and the set of UM-enabled users for whom the Unified Messaging servers answer incoming calls. Small dial plans that serve hundreds of users or fewer may have only one Unified Messaging server. Large dial plans that have several thousand users or more or that provide redundancy to help maintain UM service availability have two or more Unified Messaging servers.

Publishing custom prompts has the following benefits:

• Consistent user experience   To the user, custom prompts appear to always work in the same manner and at the same speed.

• Consistent server configuration   You do not have to make sure that each Unified Messaging server is updated correctly.

After you create a single copy of the custom audio file that you want to use as an audio prompt, greeting, or information announcement, you must make sure that all the Unified Messaging servers associated with the UM dial plan receive a copy of this custom audio file. You do this by configuring the UM dial plan or UM auto attendant to use the custom prompt by using the Exchange Management Console or by using the Copy-UMCustomPrompt cmdlet in the Exchange Management Shell.

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Architecture

When you install the Unified Messaging server role, the audio files for the system prompts are copied to a folder on the Unified Messaging server. The system prompts that are copied to the Unified Messaging server are used as the default prompts for UM dial plans and auto attendants. Because the system prompts are generic, you might want to enable custom greetings, announcements, and menu prompts in your Unified Messaging environment. You must first create your custom audio prompts, enable the custom prompts on a UM dial plan or auto attendant, and then make sure that your custom prompts are available on each Unified Messaging server that belongs to a single UM dial plan.

You can use the Exchange Management Console or the Exchange Management Shell to copy the required custom audio files. To make sure that the custom prompts are available to each Unified Messaging server, you perform the following tasks by using the Copy-UMCustomPrompt cmdlet or when you select the custom audio file in the Exchange Management Console:

• Locate the prompt publishing point in the Active Directory directory service.

• Copy the custom prompt to the prompt publishing point.

• Update the configuration for Unified Messaging in the Active Directory directory service.

After these tasks are performed, the Microsoft Exchange File Distribution service updates each Unified Messaging server that is associated with the dial plan.

Warning

We do not recommend that you use the Copy-Item cmdlet, Microsoft Windows Explorer, or another program such xcopy.exe to copy the custom prompt .wav files into a folder within the custom prompt publishing point folder.

The following figure illustrates the custom prompt publishing architecture and tasks that are performed by the Copy-UMCustomPrompt cmdlet or when you configure the dial plan or auto attendant to use a custom audio file by using the Exchange Management Console.

Custom prompt publishing architecture

The Copy-UMCustomPrompt cmdlet queries the appropriate dial plan object in Active Directory to determine the location of the prompt publishing point. There is only one prompt publishing point for each dial plan, and it is stored as a Windows file share (also known as UNC) path that identifies a file share that is available for custom prompts. After the location of the prompt publishing point is determined, the cmdlet validates the content in the custom prompt, verifies that it is in the correct format, and that it uses a supported audio codec. If the custom prompt passes the validation tests, the Exchange Management Shell command copies the prompt content to the prompt publishing point.

The custom audio files in the prompt publishing point are automatically organized into a directory structure that reflects the dial plans and auto attendants that are configured in your Exchange 2007 organization.

The following figure illustrates the prompt publishing point directory structure. In Figure 2, a prompt publishing point has various subdirectories that correspond to UM dial plans and. There are auto attendants within each dial plan.

Prompt publishing point directory structure

Each UM dial plan and UM auto attendant that is created is given a unique ID. The directory names are generated from the unique IDs that are given to the dial plan or auto attendant when their configuration objects are created. You do not have to know the exact names or locations of files under the prompt publishing point, because the Copy-UMCustomPrompt cmdlet uses the unique ID that is associated with the dial plan or auto attendant to make sure that the custom prompt is copied to the correct location in the directory structure.

After the custom prompt is copied to the prompt publishing point and any necessary directory updates are made, the prompt is copied to each Unified Messaging server in the dial plan. After the custom prompt is added to the appropriate folder on the Unified Messaging server that is configured as the prompt publishing point, the Microsoft Exchange File Distribution service that runs on each Unified Messaging server refers to the prompt publishing point and determines whether the files in the prompt publishing point have changed or if additional files have been added. If files have been changed or additional files exist, the other Unified Messaging servers pull the custom prompts from the prompt publishing point and copy them to the correct location in the \\<Server name>\ExchangeUM folder that exists on a local drive.

Note

The Microsoft Exchange File Distribution service is installed together with the Unified Messaging server role. It is also installed with the Client Access server role, because it is also used to copy the offline address book for clients that are running Microsoft Office Outlook Web Access.

All the Microsoft Exchange File Distribution service information is stored in Active Directory. However, you should back up the source locations for replicated files, such as offline address books and UM prompts. The offline address book source is the Mailbox server that generates the offline address book, and the UM prompt location is on the first Unified Messaging server, unless otherwise specified. As long as the source is backed up or restored, the Microsoft Exchange File Distribution service replicates the content. If any of the replica servers go down, Microsoft Exchange File Distribution service replicates content from the source as soon as they are back online without any administrator intervention. You can run Update-FileDistributionService to force replication if you do not want to wait for the automated process to occur.

Important

After you have configured a new custom prompt or updated one, it may take several minutes for the Microsoft Exchange File Distribution service to make the custom prompt available on all Unified Messaging servers in your Exchange 2007 organization. If you want to make the custom prompt available immediately on all the Unified Messaging servers in your organization, you must run the Update-FileDistributionService cmdlet to ensure that the custom prompt is copied to all Unified Messaging servers in your organization.

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Changing the Prompt Publishing Point

The prompt publishing point for a UM dial plan is automatically set at the time that the first Unified Messaging server joins the dial plan. It can be located on any server that can be accessed by the Unified Messaging servers that are associated with a particular dial plan. The prompt publishing point is a property that is set on a UM dial plan and is set to \\<server name>\ExchangeUM, where <server name> is replaced by the NetBIOS name of the Unified Messaging server.

For dial plans that have one Unified Messaging server, there is little reason to change the location of the prompt publishing point. However, you may want to move the prompt publishing point for the following reasons:

• In a dial plan that has multiple Unified Messaging servers, the prompt publishing point represents a single point of failure.

• A Unified Messaging server generally does not act as a file server. A Unified Messaging server may not be backed up as frequently as other servers and may not be configured to have disk storage devices such as redundant array of independent disks (RAID) arrays. If a file server that has a RAID array exists on the network, you may want to use it for the master copy of the UM custom prompts.

  Important

  You must move the prompt publishing point to another location before you can uninstall the Unified Messaging server role.

For more information about how to change the prompt publishing point, see How to Change the Prompt Publishing Point.

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Understanding Unified Messaging Languages

You can install and configure language packs to support multiple languages in Microsoft Exchange Server 2007 Unified Messaging (UM) environments.

Exchange 2007 UM language packs enable callers and Outlook Voice Access users to interact with the Unified Messaging system in multiple languages. After you install an additional language on a Unified Messaging server, callers and Outlook Voice Access users can hear e-mail messages and interact with the Unified Messaging system in this language.

Each UM language pack includes a Text-to-Speech (TTS) engine and the prerecorded prompts for a given language. UM language packs are offered in 16 different languages, and all 16 language packs are included on the Exchange 2007 DVD. However, not all the UM language packs contain support for Automatic Speech Recognition (ASR).

There are several key components that rely on UM language packs to enable users and callers to interact effectively with Exchange 2007 Unified Messaging in multiple languages. This topic discusses UM language packs, the UM components that use the UM language packs, and how the UM language packs, after they are installed, can be used to configure UM dial plans and UM auto attendants to use other languages.

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UM Language Packs

The UM language packs that are included with Exchange 2007 contain prerecorded prompts, Text-to-Speech (TTS) conversion support for a given language, and in some cases, support for Automatic Speech Recognition (ASR). In multilanguage environments, you may have to install additional UM language packs because some callers prefer to be prompted in a given language, or because they receive e-mail in more than one language. You must install multiple UM language packs to support the ability for the Unified Messaging server to read an e-mail that contains more than one language, because the TTS conversion system must be instructed which language to select based on the text of the message that will be read. If the Unified Messaging language pack has not been installed, the e-mail message will be illogical and incoherent when it is read back to the user. Installing the appropriate language pack enables the TTS engine to read e-mail and calendar items to the Outlook Voice Access user by using the correct language and also provides the language-specific prerecorded prompts for Unified Messaging. In some cases, they may also provide support for ASR.

Note

The TTS engine converts text to speech but does not convert from speech to text. A UM-enabled user can send an e-mail message that has a voice file attached to another user. However, they cannot create and send a text-based e-mail message to another user.

When you install a language pack, the installation program does the following:

1. Copies the language prompts that will be used to configure UM dial plans and auto attendants.

2. Allows the TTS engine to read messages when an Outlook Voice Access user accesses their Inbox.

3. Enables ASR for speech-enabled UM dial plans and auto attendants for the language that is installed.

Warning

You cannot use the .msi file for UM language packs to install Unified Messaging language packs. You must use Setup.com to install additional language packs.

You must add and remove UM language packs by using the Setup.com command. There is no graphical user interface or Exchange Management Shell cmdlet that you can use to add or remove languages from a Unified Messaging server. For more information about how to install a UM language pack, see How to Add a Unified Messaging Language to a Unified Messaging Server. For more information about how to remove a UM language pack, see How to Remove a Unified Messaging Language Pack from a Unified Messaging Server.

Note

By default, when you install either the U.S.-English version of Exchange 2007 or a localized version of Exchange 2007, the U.S.-English language will be installed and cannot be removed unless you remove the Unified Messaging server role from the computer.

The following table lists the Unified Messaging language packs. It also lists the file name for each UM language pack and the value for the UM language when you are using the setup.com /addUMlanguagepack or setup.com /removeUMlanguagepack commands.

UM language packs and file names

UM language pack	File name	Value
US English	umlang-en-US.msi	en-US
German	umlang-de-DE.msi	de-DE
French	umlang-fr-FR.msi	fr-FR
Japanese	umlang-ja-JP.msi	ja-JP
UK English	umlang-en-GB.msi	en-GB
Korean	umlang-ko-KR.msi	ko-KR
Spanish (Iberian)	umlang-es-ES.msi	es-ES
Mandarin (China)	umlang-zh-CN.msi	zh-CN
Mandarin (Taiwan)	umlang-zh-TW.msi	zh-TW
Dutch	umlang-nl-NL.msi	nl-NL
Italian	umlang-it-IT.msi	it-IT
Portuguese (Brazil)	umlang-pt-BR.msi	pt-BR
Swedish	umlang-sv-SE.msi	sv-SE
Australian English	umlang-en-AU.msi	en-AU
Canadian French	umlang-fr-CA.msi	fr-CA
Latin American Spanish	umlang-es-US.msi	es-US

Note

All the UM language packs that are available are located on the Exchange Server 2007 DVD. However, if you have downloaded Exchange 2007 from the Web and you need additional UM language packs, you must download them from the Unified Messaging Language Packs for Exchange Server 2007 page on the Exchange Server TechCenter.

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UM Language Components and Features

There are several key components and features in Exchange 2007 Unified Messaging that enable users and callers to interact with a multilanguage Unified Messaging system. For these components and features to work correctly and enable callers to interact with the system in multiple languages, the UM language packs must be installed correctly on a Unified Messaging server.

Prerecorded Prompts

The Exchange 2007 Unified Messaging server role is installed with a set of default audio prompts, and these audio file are the recordings that are used for menu prompts for Outlook Voice Access, voice mail greetings, and numbers that are used by Exchange Unified Messaging. These audio files are played by a Unified Messaging server to incoming internal and external callers. Many of the audio files are default prompts that provide the users of the telephony user interface (TUI) and Outlook Voice Access the information that they need to move through the TUI and the voice user interface (VUI). The prompts are located in <Program Files>\Microsoft\Exchange Server\. The prompts that are used by the Unified Messaging server to help callers move through the menus should not be replaced or changed. However, when an additional UM language pack is installed, the prerecorded prompts for that language will also be installed. After a UM language pack has been installed, the prerecorded prompts for that language can be used by UM dial plans and auto attendants.

TTS Languages

Unified Messaging relies on the Text-to-Speech (TTS) engine. TTS functionality is provided by the Microsoft Speech Server service. The TTS engine reads and converts written text into audible output that can be heard by a caller. The TTS engine reads and converts the following items in a user's mailbox:

• E-mail and voice mail message bodies, subjects, and names

• Calendar item bodies, subjects, locations, and names

• Personal contact names

• The user's default voice mail greetings

Note

After a user has recorded personalized voice mail greetings, the TTS version of their voice mail greetings is no longer used.

Automatic Speech Recognition

In addition to TTS, Automatic Speech Recognition (ASR) support is included in Exchange 2007 Unified Messaging. ASR functionality is provided by the Microsoft Speech Server service. ASR enables callers to use voice commands to interact with the Unified Messaging system. By using ASR, callers can move through menus and interact with items from their individual mailboxes, including messages, personal contacts, and calendar.

Currently, Exchange 2007 Unified Messaging includes ASR support for only the English version of Exchange 2007. Other UM language packs do not contain support for ASR. However, if you install a localized version of Exchange 2007, for example Japanese, ASR support is not included for Japanese. However, because English is always installed together with localized versions of Exchange 2007, ASR for English will work.

There are plans to include ASR support in UM language packs for other languages after Exchange 2007 has released. After new language packs have been released and after you have installed the appropriate language pack that includes ASR support for a language other than English, users will be able to use this language to interact with the Unified Messaging system by using speech input.

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Unified Messaging Languages

To enable callers to use the multilanguage features found in Exchange 2007 Unified Messaging, you must first install a UM language pack. Then you have the option of configuring other UM components.

• Install the UM language pack on the Unified Messaging server.

• If you have to, configure the default language for a UM dial plan. This lets Outlook Voice Access users who are associated with the UM dial plan use the new language when they access their mailbox. However, the user can still configure their language setting in the options that are available in Outlook Web Access.

• If you have to, configure the language setting on a UM auto attendant. By default, a UM auto attendant uses the UM dial plan language. However, you can change this setting and enable unauthenticated callers to connect to your organization and move through the auto attendant menus in the specified language.

Unified Messaging Server Languages

You install a UM language pack on the Unified Messaging server by using Setup.com. After you have installed the new language pack on the Unified Messaging server, the language associated with the language pack will be added to the list of available languages that you can use. You can view the languages that have been installed by using the UM Settings tab on the Unified Messaging server properties in the Exchange Management Console or by using the Get-UMServer cmdlet in the Exchange Management Shell.

Installing the UM language pack copies the files that are used by the TTS engine and the prerecorded prompts for the chosen language and makes them available when a user connects to the Unified Messaging system.

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UM Dial Plan Languages

Each UM dial plan that is created contains a default language setting. The UM dial plan language setting is needed because Unified Messaging may have to use Text-to-Speech conversion or play a standard audio prompt for Outlook Voice Access users when they access their Exchange 2007 mailbox. You do not have to select a default dial plan language. However, each dial plan that is created is configured to have a default language that is based on the language version of Exchange 2007 that is installed. If you install the U.S.-English version, U.S. English will be the default language for all dial plans that are created. If you installed a localized version of Exchange, for example Japanese, Japanese will be configured as the default language when dial plans are created.

After you have created a new dial plan, you can configure the default language setting on each dial plan. If you install the U.S.-English version of Exchange 2007, U.S. English will be the only available option. You can add other UM languages to the U.S.-English version by installing other UM language packs. After you install a UM language pack on a Unified Messaging server, the language associated with the language pack will also be listed as an available option when you configure the default language for the dial plan. However, U.S. English is the default language that will be used when dial plans are created.

For example, you first install the U.S.-English version of Exchange 2007 and then install the Japanese UM language pack by using the Setup.com /AddUmLanguagePack command. Then you install another UM language pack on a Unified Messaging server, for example French. After you have successfully installed the UM language packs, U.S. English, Japanese, and French, will be available options. However, by default, U.S. English is the language that will be chosen for each dial plan that is created.

When you install a localized version of Exchange 2007, for example, Japanese, the default language for the dial plan will be Japanese. However, after you have created a new dial plan, you will be able to configure the dial plan to use either Japanese or U.S. English as the default language. When localized versions of Exchange 2007 are installed, U.S. English is also installed. For example, you first install the localized Japanese version of Exchange 2007 and then install the French UM language. After you have successfully installed the UM language pack on the localized version of Exchange 2007, Japanese, U.S. English, and French, will be available but, by default, Japanese will be the language that is chosen for each dial plan that is created.

The default language is important to callers. When an Outlook Voice Access user calls in to the Unified Messaging system, the language setting that is chosen is based on the language setting that is configured in Outlook Web Access that was set when the user first logged on to their mailbox by using Outlook Web Access. Unified Messaging then compares the language that is set in Outlook Web Access to the list of available languages on the dial plan with which the user is associated. If there is no suitable match for the language, the default UM dial plan language will be used. Sometimes, you may have to set this language as the default language. For example, if you have a dial plan that contains only users from France, you may want to change the default language setting on the dial plan to French. For more information about how to change the default language for a UM dial plan, see How to Configure a Unified Messaging Dial Plan with a Default Language.

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UM Auto Attendant Languages

By default, because UM auto attendants are associated with a UM dial plan when they are created, they use the default language setting of the associated UM dial plan. However, this setting can be changed after the UM auto attendant is created.

The UM auto attendant language setting is needed because Unified Messaging may have to use Text-to-Speech conversion or play a standard audio prompt to a caller. Unified Messaging does not check that the language of custom prompts for the auto attendant matches the language setting on the auto attendant. However, as a best practice, make sure that the language setting of the auto attendant matches the language of the custom prompts. Otherwise, the caller may hear the system shift from one language to another.

Being able to change the UM auto attendant language setting is also useful if you need several different language-specific auto attendants for callers. For more information about how to configure language settings on a UM auto attendant, see How to Configure the Language Setting on a Unified Messaging Auto Attendant.

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Understanding Automatic Speech Recognition Directory Lookups

Microsoft Exchange Server 2007 Unified Messaging offers a voice user interface (VUI) that uses Automatic Speech Recognition (ASR). This is the telephone interface that callers use to navigate the menu systems and access their mailbox by using speech inputs. ASR enables callers to use speech inputs instead of dual tone multi-frequency (DTMF), also known as touchtone, inputs to navigate the UM auto attendant menus or when a UM-enabled user accesses their mailbox. This topic discusses how ASR is used in Exchange Server 2007 Unified Messaging and how grammar files are used with ASR.

Note

ASR for directory lookups and searches is currently available only in English for Outlook Voice Access users and for calls to UM auto attendants. However, support for ASR in other languages is planned for a future release.

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Overview of Grammar Files

A speech grammar file contains words and phrases that the speech engine will try to recognize when the grammar file is being used. Grammar files define things such as the commands that are available to a user while they are reviewing their mail or their calendar or the names of people who are recognized by the speech engine when a caller searches the directory. Speech grammar files are first generated as files that have a .grxml extension. They are then processed into a compiled form that has a .cfg extension before they are loaded into the speech engine. However, the .cfg file is loaded into the memory of the Microsoft Exchange Speech Engine service. Therefore, there is no .cfg file that is created and saved to a disk. The following figure illustrates how the grammar files are used by callers.

Grammar file overview

Note

  If you want to locate the .grxml file that corresponds to a .cfg file, look in the event log for events that have the IDs 1040 or 1041. The event will show which .grxml file was used to produce a particular .cfg file.

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Default Grammar Files

When the Unified Messaging server role is installed, many files are copied to the server. These files include the default grammar files that are used by ASR to enable the voice user interface (VUI). By default, these grammar files are installed in the \UnifiedMessaging\grammars\<language> folder. However, when these grammar files are used by the Unified Messaging server, they are loaded and compiled into a .cfg file by the Microsoft Exchange Speech Engine service.

The default grammar files include the following files:

• Calendar.grxml

• Common.grxml

• Contacts.grxml

• Email.grxml

• Mainmenu.grxml

Custom Grammar Files

Several custom grammar files are created when the Unified Messaging server role is installed and then again when you create Unified Messaging objects in the Active Directory directory service and the Microsoft Exchange Unified Messaging service runs grammar generation at its scheduled time, one time each day. These grammar files contain the names of users and other objects, for example distribution lists, that are in the Active Directory. For each name there is additional data, for example an e-mail alias. This data enables the name to be associated with a unique object.

The following grammar files are created when the Microsoft Exchange Unified Messaging service runs grammar generation at the scheduled time:

• Gal.grxml

• <DialPlanGUID>.grxml

• <AddressListGUID>.grxml

• DistributionList.grxml

  Note

  When a custom address list is updated, a UM-enabled user may not be immediately available for callers. You must run the update-addresslist cmdlet to update the custom address list, and then either wait until the next scheduled grammar generation to occur or manually run the galgrammargenerator.exe command to include the UM-enabled user's name in a grammar file.

When the Unified Messaging server is creating a speech grammar file, it will examine many directory objects to determine which names should be added to the speech grammar file. The types of objects that it will process are based on the scope of the grammar that is being created. However, for all these objects, Unified Messaging will not add the object to the grammar if the object is hidden from the Exchange 2007 address lists or the msExchHideFromAddressLists attribute is set to true for the object.

• For the global address list (GAL) grammar file, Unified Messaging will consider the following:

  • Mail-enabled users

  • Mail-enabled contacts

• For dial plan grammar files, Unified Messaging will consider the following:

  • UM-enabled users in the specified dial plan

• For the distribution list grammar file, Unified Messaging will consider the following:

  • Distribution lists that are visible in address lists

A default GAL is created when the Mailbox server role is installed on a computer that is running Exchange 2007. When the Unified Messaging server role is installed, it creates a grammar file for the GAL that is based on the speech grammar filters that are configured. If you create custom address lists or distribution lists in your Exchange 2007 organization, additional grammar files will be created for each custom address list or distribution list that you create.

Note

For a grammar file to be generated for a distribution list, the distribution list must not be hidden.

When you first create a UM dial plan, no grammar files are created. However, when a Unified Messaging server joins a dial plan for the first time, a single grammar file for the UM dial plan is created in the appropriate language folder. The UM dial plan speech grammar file is then filtered to include only UM-enabled users who are associated with the dial plan. The grammar files for these objects are named by using the GUIDs of the objects that they represent after they are compiled, for example, 2da514a1-06f4-44a1-9ce5-610854f7d2ee.grxml or the corresponding .cfg file.

When the grammar files for UM dial plans, the GAL, address lists, and distribution lists are created, they are created in a language-specific folder on the local Unified Messaging server. The language folder that is used is selected based on the default language that is configured on the UM dial plan. For example, if the default language on the dial plan is set to US-English (en-US), a grammar file will be created in the \UnifiedMessaging\grammars\en folder. After the grammar file has been created, it will be updated according to the schedule that is configured on the Unified Messaging server.

For more information, see the following topics:

• How to Add a Unified Messaging Server to a Dial Plan

• How to Create a New Unified Messaging Dial Plan

• How to Create a New Unified Messaging Auto Attendant

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Grammar Generation

Frequently, the default grammar generation schedule will fit your needs. However, there will be times when you must manually generate grammar files or update existing grammar files before the scheduled grammar generation task runs. There may also be times when you will want to change the default grammar generation schedule.

Grammar generation occurs in the following situations:

• When the Unified Messaging server is added to a UM dial plan, and daily after that at a scheduled interval.

• When you run the galgrammargenerator.exe command to manually update or create grammar files.

The grammar file that is created is then updated when the scheduled grammar generation task runs. To display the default grammar generation schedule for a Unified Messaging server, use the following Exchange Management Shell cmdlet:

(Get-UMServer $env:COMPUTERNAME).GrammarGenerationSchedule

For more information about the Get-UMServer cmdlet, see Get-UMServer.

By default, grammar generation occurs daily at the time that is specified by the GrammarGenerationSchedule parameter of the Unified Messaging server. By default, the schedule is defined so that grammar generation will start at 2:00 A.M. each day. However, the grammar generation schedule can be changed and is controlled by using the Set-UMserver cmdlet in the Exchange Management Shell. There is no graphical user interface that you can use to control the grammar generator schedule. This schedule can be controlled only by using the Set-UMserver cmdlet in the Exchange Management Shell. For more information about how to change the phonetic display name by using the Set-UMServer cmdlet, see Set-UMServer.

By default, the grammar generation schedule is set to start one time per day at 2:00 A.M. local time on the Unified Messaging server. After it starts, grammar generation will run until it is completed, whether this is before the scheduled end time for the active period or not; grammar generation will not run if there is another grammar generation that is running. Although you can configure additional scheduled times, grammar generation will not run within one hour of a previously scheduled grammar generation period. Because grammar generation uses a significant amount of system resources, we recommend that you configure all grammar generation schedules so that grammar generation will occur during off-peak hours. However, you can stagger the grammar generation schedules on multiple Unified Messaging servers, for example, Umserver1 starts at 2:00 A.M., Umserver2 starts at 2:30 A.M., and Umserver3 starts at 3:00 A.M. This will help minimize the effect of grammar generation on the Active Directory domain controllers.

Note

A log file that is named UMSpeechGrammar.log will be created in the %ExchangeRoot%\UnifiedMessaging\temp folder. This log file contains information about all grammar files that are created or updated on a Unified Messaging server. This file will be overwritten every time that scheduled grammar generation runs.

In the following circumstances, you can wait for the next scheduled grammar generation for the changes to be reflected, or you can force an update by using the galgrammargenerator.exe command.

• When you complete a new installation of the Unified Messaging server role and enable users for Unified Messaging

• When a UM dial plan, UM auto attendant, custom address list, or custom distribution list is created

• When you create UM-enabled users

• If you change a UM dial plan or UM auto attendant

Note

When an Outlook Voice Access user tries to locate a UM-enabled user by using the directory search feature with Automatic Speech Recognition (ASR) immediately after you have completed a new installation of the Unified Messaging server role and enabled users for UM, the caller will hear a system prompt that says, "I am sorry I could not help." Then they will be disconnected. This occurs because a grammar file for the global address list (GAL) has not been generated. Use the galgrammargenerator.exe command to create the required grammar file for the GAL.

For example, when you first enable users for UM, those users will not be available to callers who use ASR to perform a directory search until the scheduled grammar generation task runs. To make sure that those new users who were recently UM-enabled are visible to callers, run the galgrammargenerator.exe program to force the .grxml files to be created or updated and to compile the appropriate .cfg files so that callers can use ASR to move through the menu systems or locate users by using ASR.

Galgrammargenerator.exe is also useful when a Unified Messaging server has joined a dial plan and one or more speech-enabled auto attendants are associated with the dial plan. By default, callers who call into a speech-enabled auto attendant can only reach UM-enabled users who are associated with the dial plan. Before callers can be transferred to UM-enabled users by using voice inputs, a grammar file must be generated. The grammar file is not generated automatically when the server joins a dial plan. Instead, it is generated the next time grammar generation is scheduled. Grammar generation occurs according to the default schedule, at 2:00 AM local time each day, unless the schedule has been changed.

If you want UM-enabled users to be available from a directory search from the speech-enabled auto attendant immediately after you create the auto attendant, you must generate the required grammar file for the auto attendant by using galgrammargenerator.exe with the –d option.

A grammar file is not required with auto attendants that are not speech-enabled. This is because a DTMF map is added to the Active Directory for each user when they are enabled for UM. DTMF maps enable callers to enter the digits that correspond to the letters of the user's name or e-mail alias on a telephone keypad.

However, a DTMF map will not automatically be created for users who are not UM-enabled. By using galgrammargenerator.exe with the -u option, you can generate a DTMF map for all users who are mail-enabled but not UM-enabled. This lets users who are mail-enabled but not UM-enabled be reached from the auto attendant when their name or e-mail alias is entered by a caller by using DTMF inputs. For more information about the DTMF interface, see Understanding the DTMF Interface later in this white paper.

The following table lists the switches and descriptions for the switches for the galgrammargenerator.exe program.

Galgrammargenerator.exe and the switches

Switch	Description
-d <dialplan>	Creates a grammar file that contains the names of UM-enabled users only in the specified UM dial plan.
-g	Generates the grammar file.
-l	Generates a grammar file for a distribution list.
-o	Generates a log file. The path can be an absolute path, for example, C:\Logfiles. By default, the Unified Messaging server will also automatically create a log file in the \UnifiedMessaging\Temp folder.
-p	Preload all generated grammars into the Microsoft Speech Server platform.
-s <UMserver>	Creates a grammar file for each UM dial plan to which the specified Unified Messaging server belongs.
-u	Creates or updates DTMF maps for users who are enabled for UM and who are not enabled for UM. Note If a mailbox-enabled user or a mail-enabled contact has a character in their e-mail alias that is not valid and you run the galgrammargenerator.exe /u command to create a DTMF map for users, the command will not complete successfully and Unified Messaging will report an error. To ensure that all mailbox users and mail-enabled contacts have no characters in their e-mail addresses that are not valid, use the Get-User cmdlet to view all users. The Get-User cmdlet will perform a validation check for the user attributes. If any field has a character that is not valid, an error will be generated that identifies the recipient and the field that contains the character.
-x	Defines the speech filter list that is used in XML format.

Note

The default speech grammar filter list (SpeechGrammarFilterList.xml) is installed in the %ExchangeRoot%\bin folder on each server that has the Unified Messaging server role installed. The contents of the speech filter list file must be the same on each Unified Messaging server. The speech grammar filter list contains several rules that specify input patterns against which display names are matched and output patterns that define transformations of the matched name. If the name matches a pattern it will be replaced in the speech grammar by the name or names that are generated from the associated output pattern or patterns. If the name does not match a pattern, it is passed through unchanged to the speech grammar. Names will be rejected from insertion in the speech grammar if they to have two or more distinct ways of being said. We recommend that you do not manually modify the SpeechGrammarFilterList.xml file.

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Customizing Grammar Files

Currently, ASR is available only in English and includes the prerecorded prompts and text-to-speech support for English. Although ASR support is included in the English language pack, there will be times when it is difficult for speech recognition to locate the correct UM-enabled user because the user has a name that is difficult to pronounce, the caller's speech is matched against the wrong name, or the caller speaks a form of the user's name that differs from the name that exists in the speech grammar. However, adding an additional UM language pack will not resolve this problem.

Unified Messaging uses two Active Directory attributes to generate names to use with ASR grammar files: Display name (displayName) and Phonetic display name (msDS-PhoneticName). By default, Unified Messaging uses the displayName attribute to recognize the name of a user when a caller speaks their name. This works well if the user's name is easy to pronounce. However, in some cases, users have names that are difficult to pronounce. To help Unified Messaging find users whose names are difficult to pronounce, we recommend that you configure the Unified Messaging system by supplying a phonetic display name for users who have names that ASR has trouble recognizing. However, to supply a phonetic display name, you must predict how the speech engine would perceive a certain spelling of a name to provide an accurate pronunciation for the phonetic name.

Note

By default, the Unified Messaging server will try to insert both the phonetic display name, if one exists, and the display name into the speech grammar file.

For example, the display name "Kweku Ako-Adjei" could be given a phonetic display name of "Quaykoo Akoo Oddjay", and UM would insert that into the speech grammar file. The drawback to creating phonetic names for users is that it is difficult to do on a large scale. It would be very time-consuming to create and test phonetic display names for every user whose name is not correctly recognized by ASR, especially in large enterprise environments.

To add or change the phonetic display name for a UM-enabled user, you must use ADSI Edit (AdsiEdit.msc) or the Set-User Exchange Management Shell cmdlet. You cannot use Active Directory Users and Computers or the Exchange Management Console to change a user's phonetic display name. For more information about how to change a phonetic display name by using the Set-User cmdlet, see Set-User.

The PhoneticDisplayName parameter specifies a phonetic pronunciation for the display name. The display name is specified by using the DisplayName parameter. If the display name is not easy for the Unified Messaging server to pronounce or recognize, you can use the PhoneticDisplayName parameter to specify a phonetic version. If you specify a value, it is used by ASR to recognize the user's name and by the Text to Speech (TTS) engine to pronounce the user's name. If you do not specify a value, the Unified Messaging server uses the DisplayName parameter. The maximum length of this parameter value is 255 characters. For more information about ADSI Edit, see Adsiedit Overview.

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Understanding the DTMF Interface

In Microsoft Exchange Server 2007 Unified Messaging (UM), callers can use dual tone multi-frequency (DTMF), also referred to as touch-tone, and voice inputs to interact with the system. The method callers can use depends on how the UM dial plans and auto attendants are configured.

The DTMF interface enables callers to use the telephone keypad to locate users and navigate the UM menu system when they call a subscriber access number that is configured on a dial plan or when they call a telephone number that is configured on an auto attendant. This topic discusses the DTMF interface and how it is used by callers to locate users and to navigate the Exchange 2007 Unified Messaging menu system.

For more information about how voice inputs are used in Unified Messaging, see Understanding Automatic Speech Recognition Directory Lookups earlier in this white paper.

DTMF Overview

DTMF requires a caller to press a key on the telephone keypad that corresponds to a Unified Messaging menu option or to input a user's name by using the letters on the keys to spell the user's name or e-mail alias. Callers might use DTMF because Automatic Speech Recognition (ASR) has not been enabled or because they tried to use voice commands and failed. In either case, DTMF inputs are used to navigate menus and search for users.

By default, in Exchange 2007 Unified Messaging, DTMF inputs are used on dial plans and are the default caller interface for UM auto attendants.

Note

Only auto attendants that are configured to use English can be speech-enabled.

DTMF inputs may be used by callers for:

• Dial plan subscriber access by using Outlook Voice Access.

• Dial plan directory lookups and searches to locate users.

• Auto attendants that are not speech-enabled.

• Auto attendants that are speech-enabled that do or do not have a DTMF fallback auto attendant configured.

• DTMF fallback auto attendants (not speech-enabled).

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UM Dial Plans and Dial by Name

When you create a UM dial plan, you can configure the primary and secondary input method that callers will use to look up names when they search for a user or want to contact a user. These settings are located on the dial plan's Settings tab and are called Dial by name primary method and Dial by name secondary method. The following options are available for the Dial by name primary method and the Dial by name secondary method:

• Last First

• First Last

• SMTP Address

Additionally, None is an available option on the Dial by name secondary method.

By default, Last First is selected for the Dial by name primary method and SMTP Address is selected as the Dial by name secondary method. Therefore, when a caller dials in to the subscriber access number that is configured on the UM dial plan, the dial plan's welcome message will be played and the operator will say something like, "Welcome to Contoso Outlook Voice Access. To access your mailbox, enter your extension. To contact someone, press the # key." After the caller has pressed the # key, the system will respond with "Spell the name of the person you are calling, last name first, or to spell their e-mail alias, press the # key twice." In this scenario, depending on how your dial plan is configured, the system then prompts the caller to enter the user's last name first and then the user's first name (Last First) or to spell their e-mail alias, excluding the domain name.

For example, if the user's e-mail alias is tsmith@contoso.com, the caller would enter tsmith. If you want to change this configuration because the default setting does not meet your needs, you can change it to enable callers to enter the users e-mail alias first or the user's first name followed by their last name. In this case, you would configure the Dial by name primary method with the SMTP Address setting and configure the Dial by name secondary method with the First Last setting. The settings for the dial by name methods will also apply to any UM auto attendants that are associated with the dial plan. For callers to be able to enter the name of the user by using DTMF inputs or the keys on the telephone keypad, a DTMF map and values for the user must exist within the Active Directory directory service.

For more information about how to change the dial by name primary and secondary methods on a Unified Messaging dial plan, see How to Change the Dial by Name Primary Method on a Unified Messaging Dial Plan and How to Change the Dial by Name Secondary Method on a Unified Messaging Dial Plan.

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DTMF Maps

In an Exchange 2007 organization, an attribute named msExchUMDtmfMap is associated with each user that is created in Active Directory. This attribute is used by Unified Messaging to map the user's first name, last name, and e-mail alias to a set of numbers. This mapping is referred to as a DTMF map. A DTMF map enables a caller to enter the digits on the telephone keypad that correspond to the letters of the user's name or e-mail alias. This attribute contains the values that are needed to create a DTMF map for the user's first name followed by their last name, for the user's last name followed by their first name, and for the user's e-mail alias.

The following table shows the DTMF map values that would be stored in Active Directory on the msExchUMDtmfMap attribute for a UM-enabled user named Tony Smith with an alias of tsmith@contoso.com.

DTMF values that are stored in Active Directory for a UM-enabled user named Tony Smith

Active Directory entry	User's name
firstNameLastName:866976484	tonysmith
lastNameFirstName:764848669	smithtony
emailAddress:876484	tsmith

• Names and e-mail aliases may contain other non-alphabetic characters such as commas, hyphens, underscores, or periods. Characters such as these will not be used in a DTMF map for a user. For example, if the e-mail alias for Tony Smith is tony-smith@contoso.com, the DTMF map value would be 866976484 and the hyphen would not be included. However, if a user's e-mail alias contains a number or numbers, for example, tonysmith123@contoso.com, the numbers would be used in the DTMF map that is created. The DTMF map for tonysmith123 would be 866976484123.

A DTMF map must exist for a user for callers to be able to enter the user's name or e-mail alias. However, in some cases, not all users will have a DTMF map associated with their user account.

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DTMF Maps for Users Who Are Not Enabled for UM

Users, including mailbox-enabled users, are not enabled for Unified Messaging by default. Therefore, the msExchUMDtmfMap attribute is not populated with the values that are needed for a DTMF map for those users. The following figure illustrates the properties of a user for which the msExchUMDtmfMap attribute has not been populated.

msExchUMDtmfMap attribute without values

Because the users shown in the previous diagram do not have DTMF map values defined for their user accounts, callers will be unable to contact them when they press a telephone key from a UM auto attendant menu or perform a directory search. Also, UM-enabled users will be unable to send messages or transfer calls to users who do not have a DTMF map unless they can use ASR. To enable callers to transfer calls or contact non UM-enabled users by using the telephone keypad, you must create the necessary values for the DTMF map for users. To create the values for a DTMF map for users who are not enabled for Unified Messaging, you can run the galgrammargenerator.exe -u command. This command updates the DTMF maps for all users within your Microsoft Exchange. The galgrammargenerator.exe command updates or creates DTMF maps for all non UM-enabled users. You can use the Set-User cmdlet with the -CreateDtmfMap parameter to create and update a single user's DTMF map or update a DTMF map for a user if the name of the user was changed after a DTMF map was already created. Optionally, you can create an Exchange Management Shell script by using this cmdlet to update the DTMF map values for multiple users.

For more information about the Set-User Exchange Management Shell cmdlet, see Set-User.

For more information about galgrammargenerator.exe, see Understanding Automatic Speech Recognition Directory Lookups earlier in this white paper.

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DTMF Maps for Users Who Are Enabled for UM

A DTMF map is created for each UM-enabled user so that callers can contact them. By default, a DTMF map is created for users when they are enabled for Unified Messaging. This makes it possible for calls to be transferred to a UM-enabled user from external callers, non users who are not enabled for UM, and other UM-enabled users who use the telephone keypad to spell the user's name or e-mail alias. The following figure illustrates the properties on a user account where the msExchUMDtmfMap attribute has been populated with DTMF map values.

msExchUMDtmfMap attribute with values

After the DTMF map values have been created for a UM-enabled user, callers can use the directory search feature. Callers use directory search when they use the telephone keypad to in the following situations:

• To identify or search for a user when they call in to the subscriber access number

• To locate or transfer calls to a UM-enabled user when they call in to a UM auto attendant.

For more information about how to enable a user for Unified Messaging, see How to Enable a User for Unified Messaging.

Sometimes a user's first name, last name, or e-mail alias changes after they have been enabled for Unified Messaging. The user's DTMF map values will not be updated automatically in Active Directory. If a caller enters the user's new last name or e-mail alias and the user's DTMF map has not been updated to reflect the change to the name or e-mail alias, the caller will be unable to locate the user in the directory, send a message to the user, or transfer calls to the user. If you have to update a user's DTMF map after they have been enabled for Unified Messaging, you can use the Set-User cmdlet with the -CreateDtmfMap parameter. You can also create an Exchange Management Shell script by using this cmdlet if you want to update the DTMF maps for multiple UM-enabled users.

Note

You can also use the galgrammargenerator.exe -u command to update the DTMF map for UM-enabled users. However, if you use the galgrammargenerator.exe -u command, it will update or create DTMF maps for all users.

Warning

We do not recommended that you manually change the DTMF values for users by using a tool such as ADSI Edit because it might result in inconsistent configurations or other errors. We recommend that you only use galgrammargenerator.exe or the Set-User cmdlet to create or update DTMF maps for users.

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Understanding Storage Quotas and Voice Mail

When a caller leaves a voice message for a UM-enabled user, the storage quotas or limits that are configured on the user's mailbox may prevent voice messages from being delivered correctly. This topic discusses the relationship between the configuration of the computer that is running Microsoft Exchange Server 2007 that has the Unified Messaging server role installed and the storage quotas that could potentially prevent a caller from recording a voice message.

UM Dial Plans

Although there are many Active Directory objects that must be created and configured when Exchange 2007 Unified Messaging is deployed, UM dial plan objects are the central component of the Unified Messaging system. A UM dial plan object is an Exchange 2007 organization-wide object that is created in the Active Directory directory service.

After you install the Unified Messaging server role, you must associate the Unified Messaging server with at least one UM dial plan. You can also associate a single Unified Messaging server with multiple UM dial plans. For more information about how to create a new UM dial plan, see How to Create a New Unified Messaging Dial Plan.

There are many configuration settings that you can change after you create a UM dial plan to meet the needs of your organization. After you create a UM dial plan, you can configure subscriber access numbers, greetings, message properties, and other UM dial plan features. Although there are many settings that can be changed to control your Unified Messaging environment, one of the more important mailbox settings is storage quotas. If you do not set the storage quotas for users correctly, you might unintentionally prevent voice messages from being recorded for Exchange users in your organization.

Because Windows Media Audio (.wma) and .wav files are attached to each voice message, voice messages may be larger than e-mail messages. This may cause problems for users by filling up their mailbox more quickly than e-mail messages that do not include attachments. When you plan your storage quotas for users, you should consider the maximum length of a voice message that a caller will leave. Very long voice messages create large files. However, you can control the size of the voice files by reducing the length of time that callers have to leave a voice message.

The Maximum recording duration (minutes) setting controls the maximum length for the recorded messages from callers. This setting can range from 5 to 100 minutes, but the default setting is 20 minutes. You can change this setting by using the Exchange Management Console or by using the Set-UMDialPlan cmdlet in the Exchange Management Shell. For more information about how to configure settings on a UM dial plan, see How to Modify a Unified Messaging Dial Plan.

In some Exchange environments, the default setting of 20 minutes may be too high or too low. If the storage quota is set too high, you may risk taking up too much storage space on your Exchange servers or users may exceed their storage quotas too quickly. If the storage quota is set too low, it may frustrate callers by not giving them enough time to leave a whole message. Callers may then have to call back to leave another voice message for the user.

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Storage Quotas

Users may store too many e-mail, voice, and fax messages in their mailbox, in addition to attached files. If users in your organization store lots of e-mail messages, voice messages, fax messages, and attached files, you may have to limit the storage space that is allocated to each user's mailbox to reduce the storage demands on your computers that are running Exchange 2007. Frequently, large mailbox stores lead to long backup and restore times. Large mailbox stores may also affect the availability and reliability of your Exchange environment. Therefore, we recommend that you control the size of users' mailboxes to avoid running out of storage space on your Exchange servers. When users do not have a storage quota configured or they have a large storage quota configured, they could possibly fill up the disk drives on an Exchange server. To prevent this, enable and configure storage quotas on users' mailboxes. By default, and starting with the first installation, each new mailbox database includes the following default limits:

• Warning - 1991680 KB

• Prohibit Send - 2097152 KB

• Prohibit Send/Receive - 2411520 KB

After you configure storage quotas, if a storage limit is exceeded, the mailbox-enabled user is warned or prohibited from sending or receiving e-mail. You can use the default storage limits, or you can set your own storage limits to control the amount of data that can be stored in a user's mailbox. For more information about how to manage recipient storage quotas, see Managing User Mailboxes.

Because storage quotas are implemented in most Exchange environments, there may be times when a caller cannot leave a voice message for a user. Make sure that you understand the effect that setting storage quotas can have on your Unified Messaging environment and correctly plan your storage quotas for users so that voice messages are recorded correctly.

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Voice Mail Delivery

The following three scenarios describe what can occur when a voice message is delivered to a user's mailbox in different circumstances:

• The voice message fits into the user's mailbox.

• The voice message cannot fit into the user's mailbox and it fills up the remaining storage space in the user's mailbox.

• The user's mailbox has already reached its storage capacity.

In the first scenario, the telephone rings and there is no answer. The call is transferred to the Private Branch eXchange (PBX) and then to the Unified Messaging server. The Unified Messaging server checks the user's mailbox storage quota. If the user's mailbox has not reached its storage limit and a voice message is created by the Unified Messaging server for the caller, the voice message is submitted to a computer that has the Hub Transport server role installed. The Hub Transport server then routes and submits the voice message to the appropriate Mailbox server. Because the voice message does not exceed the storage quota set for the user's mailbox and the storage quota has not already been reached, the voice message is delivered to the mailbox of the intended recipient.

In the second scenario, the Unified Messaging server checks the user's mailbox storage quota. If the user's mailbox has not reached the storage limit, the voice mail message is submitted to a Hub Transport server. The Hub Transport server routes the voice mail message to the appropriate Mailbox server. The voice message is submitted to the Mailbox server, but the voice message fills up the remaining storage space and exceeds the set storage quota for the user. When this occurs, the voice message is still delivered. Even though the storage quota is exceeded when the voice message is delivered, the voice message is still delivered the same way a non-delivery report (NDR) is delivered to a user even though the mailbox has reached its capacity.

The following figure illustrates how a voice message is submitted when the user's storage quota has not been reached and how a message is submitted when a voice message causes the storage quota to be reached for the user's mailbox.

Submission of voice mail when a user's storage quota has been reached before delivery or when the voice message was delivered to the mailbox but then exceeded the mailbox quota

In the third scenario, the Unified Messaging server checks the user's mailbox storage quota. Because the user's mailbox has already reached its storage capacity, the Unified Messaging server will not record a voice message and informs the caller that the recipient's mailbox is full. The user must delete or archive messages to reduce the size of their mailbox to be lower than the storage quota to be able to receive voice messages again.

The following figure illustrates how a call is handled when a user's mailbox storage quota has been reached.

How a call is handled when a user's mailbox storage quota has been reached

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Understanding Unified Messaging VoIP Security

An important aspect of your network security is the ability to protect your Unified Messaging infrastructure. There are components within your Unified Messaging environment that you must correctly configure to help protect the data that is sent and received from Unified Messaging servers on your network. These include components such as Unified Messaging servers and dial plans. This topic discusses how you can increase protection for the Unified Messaging network data and servers in your organization. You must follow these steps to help secure your Unified Messaging environment and enable Voice over IP (VoIP) security:

1. Install the Unified Messaging server role.

2. Create a UM dial plan and configure the UM dial plan to use VoIP security.

3. Associate the Unified Messaging servers with the UM dial plan.

4. Export and import the required certificates to enable the Unified Messaging servers, IP gateways, IP Private Branch eXchanges (IP PBXs), and other servers that are running Microsoft Exchange Server 2007 to use Mutual Transport Layer Security (mutual TLS).

5. Configure the UM IP gateways that are used to have a fully qualified domain name (FQDN).

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Protecting Unified Messaging

There are several security methods that can help you protect your Unified Messaging servers and the network traffic that is sent between your IP gateways and Unified Messaging servers and between your Unified Messaging servers and other Exchange 2007 servers in your organization. The following table lists some possible threats to your Unified Messaging infrastructure and the security methods that can be implemented to help protect it.

Protecting Unified Messaging

What am I protecting against?	How can I protect it?
Monitoring voice traffic	Use Internet Protocol security (IPsec). However, the IP gateway or IP PBX must support IPsec. Use Secure Realtime Transport Protocol (SRTP).
Monitoring fax traffic	Use IPsec. However, the IP gateway or IP PBX must support IPsec.
An attack against an IP gateway or IP PBX	Use strong authentication methods. Use strong administrative passwords. Use Secure Sockets Layer (SSL) to protect administrative credentials. The IP gateway or IP PBX must support SSL. Use Secure Shell (SSH) instead of Telnet.
Unauthorized long distance calls	Use UM dial plan rules and dialing restrictions. These can be configured on the UM dial plan and UM mailbox policies. Optionally, you may be able to enforce other dialing restrictions by configuring your PBX.
A denial of service attack	The Unified Messaging server communicates only with UM IP gateways or IP PBXs that are included in the list of trusted VoIP devices or servers. This list of trusted VoIP devices or servers is created when a UM IP gateway is created in the Active Directory directory service. Use mutual TLS.
A Session Initiation Protocol (SIP) proxy impersonation	Use mutual TLS. Use IPsec. However, the IP gateway or IP PBX must support IPsec. Configure trusted LANs such as VLANs, dedicated WAN circuits, or virtual private networks (VPNs).
Eavesdropping and session hijacking	Use mutual TLS to reduce signaling eavesdropping. Use IPsec. However, the IP gateway or IP PBX must support IPsec. Configure trusted LANs such as VLANs, dedicated WAN circuits, or VPNs.

There are several security methods listed in the previous table that you can use to protect your Unified Messaging environment. One of the most important mechanisms for protecting your Unified Messaging infrastructure and the network traffic that is generated by Unified Messaging is mutual TLS.

You can use mutual TLS to encrypt Voice over IP (VoIP) traffic that is passed between IP gateways, IP PBXs, and other Exchange 2007 servers and the Unified Messaging servers on your network. The best choice for protecting this data is to use mutual TLS to encrypt the VoIP data.

However, depending on the security threat, you can also configure IPsec policies to enable data encryption between IP gateways or IP PBXs and a Unified Messaging server or between a Unified Messaging server and other Exchange 2007 servers on your network. In some environments, you might be unable to use IPsec because IPsec may be unavailable or may not be supported on the IP gateways or IP PBXs. Additionally, IPsec puts an additional processing load on system resources on Unified Messaging servers. Considering these two factors, mutual TLS is a better choice for protecting the VoIP network traffic in your Unified Messaging environment.

After you have correctly implemented and configured mutual TLS, the VoIP traffic between the IP gateways, IP PBXs, and from other Exchange servers to the Unified Messaging servers will be encrypted. However, when mutual TLS cannot be used to help secure the traffic that is sent or received from a Unified Messaging server, such as when a Unified Messaging server communicates with another server on your network, such as an Active Directory domain controller or an Exchange 2007 Mailbox server, other types of encryption are used to protect the data. The following figure shows the methods of encryption that you can use to protect Unified Messaging.

UM VoIP security

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Types of Certificates

Digital certificates are electronic files that work like an online passport to verify the identity of a user or computer and are used to create an encrypted channel that is used to protect data. A certificate is basically a digital statement that is issued by a certification authority (CA) that vouches for the identity of the certificate holder and enables the parties to communicate in a secure manner by using encryption. They can be issued by a trusted third-party CA, such as by using Certificate Services, or be self-signed. Each type of certificate has its advantages and disadvantages. However, certificates are always tamper-proof, and cannot be forged. Certificates can be issued for a variety of functions, such as Web user authentication, Web server authentication, S/MIME, IPsec, Transport Layer Security (TLS), and code signing.

A certificate binds a public key to the identity of the person, computer, or service that holds the corresponding private key. The public and private keys are used by both the client and the server to encrypt the data before it is transmitted across the wire. Certificates are used by a variety of public key security services and applications that provide authentication, data integrity, and secure communications across networks such as the Internet. For Windows-based users, computers, and services, trust in a CA is established when there is a copy of the root certificate in the trusted root store and the certificate contains a valid certification path. This means that no certificates in the certification path have been revoked or have had the validity period expire.

Digital certificates do the following:

• They authenticate that their holders—people, Web sites, and even network resources such as routers—are truly who or what they claim to be.

• They protect data that is exchanged online from theft or tampering.

There are traditionally three options or kinds of certificates that Unified Messaging and IP gateways or IP PBXs can use. In all three approaches or options, the public key of the certificate owner is part of the certificate so that the server, user, Web site, or other resource that is on the other end can decrypt the messages. The private key is known only to the signer of the certificate. Each certificate has an EnhancedKeyUsage attribute set on it to dictate the specific usage for the certificate. For example, usage could be specified only for server authentication or for use with the encrypting file system. Unified Messaging uses the certificate for server authentication and data encryption.

Self-Signed Certificates

A self-signed certificate is a certificate that is signed by its own creator. The subject and the name of the certificate match. On self-signed certificates, the issuer and subject are defined on the certificate. Self-signed certificates do not require the presence of a CA from your organization or from a third party. You must configure these certificates explicitly and copy them to the trusted root certificate store on each IP gateway, IP PBX, other Unified Messaging servers, and other Exchange 2007 computers if they are to be trusted by the Unified Messaging server that has issued the certificate.

If a public key infrastructure (PKI)-based or third-party certificate is unavailable, the Unified Messaging server will search for a self-signed certificate in the local certificate store. If it cannot find a PKI or third-party certificate, it will generate a self-signed certificate for mutual TLS. However, because it is a self-signed certificate, it will not be trusted by the IP gateways, IP PBXs on the network, or other servers on the network. To make sure that the self-signed certificate is trusted by IP gateways, IP PBXs, or other servers, you have to import the self-signed certificate into the local trusted root certificate store for the devices and servers. After you do this, when the Unified Messaging server presents this self-signed certificate to the IP gateway, IP PBX, or server, it will be able to verify that the certificate was issued by a trusted authority because the issuer will equal the subject that is defined on the self-signed certificate.

If you are using only self-signed certificates, you must import a single self-signed certificate for each IP gateway, IP PBX, or server. In large network environments that have multiple devices or computers, this may not be the best choice for implementing mutual TLS. Using self-signed certificates in a large enterprise network does not scale well because of the additional administrative overhead. However, administrative overhead is not a problem if you have multiple devices and you are using a PKI or commercial third-party certificate. This is because each device has a certificate that has been issued by the same trusted root authority. Having a certificate from the same trusted root authority guarantees that all IP gateways, IP PBXs, and other servers trust the Unified Messaging server.

For mutual TLS to work using self-signed certificates:

1. Take the Unified Messaging server's self-signed certificate and import it into the trusted root certificate store on each IP gateway and IP PBX and on other servers that the Unified Messaging server will communicate with by using mutual TLS.

2. Take the self-signed certificate from each IP gateway, IP PBX, and other server and import it into the Unified Messing server's trusted root certificate store. If you are using a PKI or third-party certificate, you will import the certification authority's certificate into the trusted root certificate store on all devices and servers.

Self-signed certificates are frequently not the best certificate option when you deploy mutual TLS or certificate-based authentication. However, smaller organizations with a limited number of devices or computers may decide to use the self-signed certificate method because it is the most easy to configure and the least expensive method to use when you implement mutual TLS. Frequently, smaller organizations decide not to use a third-party certificate or to install their own PKI to issue their own certificates because of the expense, because their administrators lack the experience and knowledge to create their own certificate hierarchy, or for both reasons. The cost is minimal and the setup is simple when you are using self-signed certificates. However, establishing an infrastructure for certificate life-cycle management, renewal, trust management, and revocation is much more difficult with self-signed certificates. For more information about how to create a certificate for TLS, see Creating a Certificate or Certificate Request for TLS.

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Public Key Infrastructure

A public key infrastructure (PKI) is a system of digital certificates, certification authorities (CAs), and registration authorities (RAs) that verify and authenticate the validity of each party that is involved in an electronic transaction by using public key cryptography. When you implement a CA in an organization that uses Active Directory, you provide an infrastructure for certificate life-cycle management, renewal, trust management, and revocation. These qualities provide a solid infrastructure for all the certificates in your organization. However, there is some cost involved in deploying additional servers and infrastructure to create and manage these types of certificates.

You can install Certificate Services on any server in the domain. If you obtain certificates from a domain Windows-based CA, you can use the CA to request or sign certificates to issue to your own servers or computers on your network. This enables you to use a PKI that resembles using a third-party certificate vendor but is less expensive. Although these PKIs cannot be deployed publicly, as other types of certificates can be, when a PKI is used, a CA signs the requestor’s certificate by using the private key and the requestor is verified. The public key of this CA is included with the certificate that is issued by the CA. Anyone who has this CA’s certificate as a root certificate can use that public key to decrypt the requestor’s certificate and authenticate the requestor.

When you use a PKI certificate to implement mutual TLS, you must copy the required certificates to the IP gateways or IP PBXs. Then you must copy the certificates on the IP gateways or IP PBXs to the Unified Messaging servers that are associated with the UM dial plan that has been configured in secure mode.

The setup and configuration for using PKI certificates and third-party certificates resemble the procedures that you perform when importing and exporting the self-signed certificates. However, you must not only install the computer certificate into the trusted root certificate store. You must also import or copy the trusted root certificate for the PKI into the trusted root certificate store on the Unified Messaging servers and the IP gateways and IP PBXs on your network.

To deploy mutual TLS when you have already deployed a PKI infrastructure, follow these steps:

1. Generate a certificate request on each IP gateway or PBX.

2. Copy the certificate request to use when requesting the certificate from a certification authority.

3. Request a certificate from the certification authority by using the certificate request. Save the certificate.

4. Import the certificate that you saved onto each device or computer.

5. Download the trusted root certificate for your PKI.

6. Import the trusted root certificate from your PKI on each device. If you are importing the trusted root certificate on an Exchange 2007 computer that is running the Unified Messaging role, you can also use Group Policy to import the trusted root certificate into the trusted root certificate store on the Unified Messaging server or other Exchange 2007 servers. However, this process is also used when you are configuring a server that is running the Unified Messaging server role.

   Note

   You will use the same steps if you are using a commercial third-party certificate to implement mutual TLS.

For more information about certificates and PKIs, see the following topics.

• For more information about certificates, see Public Key Infrastructure for Windows Server 2003.

• For more information about best practices for implementing a Microsoft Windows Server 2003 public key infrastructure, see Best Practices for Implementing a Microsoft Windows Server 2003 Public Key Infrastructure.

• For more information about how to deploy a Windows-based PKI, see the Windows Server 2003 PKI Operations Guide.

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Third-Party Certification Authorities

Third-party or commercial certificates are certificates that are generated by a third-party or commercial CA and then purchased for you to use on your network servers. One problem with self-signed and PKI-based certificates is that, because the certificate is not trusted, you must make sure that you import the certificate into the trusted root certificate store on client computers, servers, and other devices. Third-party or commercial certificates do not have this problem. Most commercial CA certificates are already trusted because the certificate already resides in the trusted root certificate store. Because the issuer is trusted, the certificate is also trusted. Using third-party certificates greatly simplifies deployment.

For larger organizations or organizations that must publicly deploy certificates, it is best to use a third-party or commercial certificate, even though there is a cost associated with the certificate. Commercial certificates may not be the best solution for smaller and medium-size organizations, and you might decide to use one of the other certificate options that are available.

Depending on the configuration of the IP gateway or IP PBX, you might still have to import the third-party or commercial certificate into the trusted certificate store on the IP gateways and IP PBXs to be able to use the third-party certificate for mutual TLS. However, in some cases, the third-party certificate will be included in the trusted root certificate store on your Unified Messaging server and other Exchange 2007 computers in your organization.

The procedures that you perform to use a commercial third-party certificate for enabling mutual TLS are the same procedures that you perform when you use a PKI certificate. The only difference is that you will not have to generate a PKI certificate because you have purchased a certificate from a commercial third-party certificate vendor that will be imported into the trusted root certificate store on the servers and devices on your network.

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Configuring Mutual TLS

By default, when an incoming call is received from an IP gateway, the VoIP traffic is not encrypted and does not use mutual TLS. However, the security setting for a Unified Messaging server is configured on the Unified Messaging dial plan that is associated with the Unified Messaging server. To enable the Unified Messaging server to communicate securely with IP gateways, IP PBXs, and other Exchange 2007 servers, you must use the Set-UMDialPlan cmdlet to configure VoIP security on the UM dial plan, and then enable mutual TLS for the Unified Messaging servers that are associated with the UM dial plan.

Note

If the Microsoft Exchange Unified Messaging service is already running and you add the Unified Messaging server to a UM dial plan, you must restart the Microsoft Exchange Unified Messaging service for the security setting on the dial plan to be enforced.

After you have enabled VoIP security on the UM dial plan, all Unified Messaging servers that are associated with the UM dial plan can communicate in a secure manner. However, depending on the type of certificate that you use for enabling mutual TLS, you must first import and export the required certificates both on the Unified Messaging servers and the IP gateways and PBXs. After the required certificate or certificates have been imported on the Unified Messaging server, you must restart the Microsoft Exchange Unified Messaging service to be able to use the certificate that was imported to establish an encrypted connection with the IP gateways or IP PBXs. For more information about how to import and export certificates, see Importing and Exporting Certificates.

After you have successfully imported and exported the required trusted certificates, the IP gateway will request a certificate from the Unified Messaging server, and then it will request a certificate from the IP gateway. Exchanging the trusted certificates between the IP gateway and the Unified Messaging server enables the IP gateway and Unified Messaging server to communicate over an encrypted connection by using mutual TLS. When an incoming call is received by an IP gateway or IP PBX, it will initiate a certificate exchange and negotiate security by using mutual TLS with the Unified Messaging server. The Microsoft Exchange Unified Messaging service is not involved in the certificate exchange process or in determining whether the certificate is valid. However, if a trusted certificate cannot be located on a Unified Messaging server, a trusted certificate is found but is not valid, or a call is rejected because of a mutual TLS negotiation failure, the Unified Messaging server will receive a notification from the Microsoft Exchange Unified Messaging service.

Although the Microsoft Exchange Unified Messaging service does not participate in the certificate exchange between the Unified Messaging server and the IP gateways, the Microsoft Exchange Unified Messaging service does the following:

• Provides a list of fully qualified domain names (FQDNs) to the Microsoft Exchange Speech service so that calls from only the IP gateways or IP PBXs that are included on the list are accepted.

• Passes the issuerName and SerialNumber attributes of a certificate to the Microsoft Exchange Speech service. These attributes uniquely identify the certificate that the Unified Messaging server will use when an IP gateway or IP PBX requests a certificate.

After the Unified Messaging server and the IP gateways or IP PBXs have performed the key exchange to establish an encrypted connection by using mutual TLS, the Unified Messaging servers will communicate with the IP gateways and IP PBXs by using an encrypted connection. The Unified Messaging servers will also communicate with other Exchange 2007 servers, such as Client Access servers and Hub Transport servers, by using an encrypted connection that uses mutual TLS. However, mutual TLS will only be used to encrypt the traffic or messages that are submitted from the Unified Messaging server to a Hub Transport server.

Important

To be able to enable mutual TLS between a UM IP gateway and a dial plan that is operating in secure mode, you must first configure the UM IP gateway with an FQDN and configure the UM IP gateway to listen on port 5061. To configure a UM IP gateway, run the following command: Set-UMIPGateway -identity MyUMIPGateway -Port 5061.

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IPsec

IPsec also uses certificates to encrypt data. It provides a key line of defense against private network and Internet attacks.

IPsec has the following goals:

• To protect the contents of IP packets.

• To defend against network attacks through packet filtering and the enforcement of trusted communication.

IPsec is a framework of open standards that helps ensure private, secure communications over IP networks by using cryptographic security services.

IPsec uses cryptography-based protection services, security protocols, and dynamic key management. It provides the strength and flexibility to protect communications between private network computers, domains, sites, remote sites, extranets, and dial-up clients. It can even be used to block receipt or transmission of specific types of traffic.

IPsec is based on an end-to-end security model that establishes trust and security from a source IP address to a destination IP address. The IP address itself does not have to be considered an identity. Instead, the system behind the IP address has an identity that is validated through an authentication process. The only computers that must know about the traffic that is being secured are the sending and receiving computers. Each computer handles security at its respective end and operates under the assumption that the medium over which the communication occurs is not secure. Computers that route data only from source to destination are not required to support IPsec unless firewall-type packet filtering or network address translation is being done between the two computers. This enables IPsec to be deployed successfully for the following organizational scenarios:

• LAN: client-to-server, server to server, and server-to-VoIP device

• WAN: router-to-router and gateway-to-gateway

• Remote access: dial-up clients and Internet access from private networks

Typically, both sides require IPsec configuration to set options and security settings that will allow two systems to agree on how to help secure traffic between them. This is known as an IPsec policy. The Microsoft Windows 2000 Server, Windows XP, and the Windows Server 2003 family implementations of IPsec are based on industry standards that were developed by the Internet Engineering Task Force (IETF) IPsec working group. Parts of IPsec-related services were jointly developed by Microsoft and Cisco Systems, Inc. For more information about how to configure IPsec policies, see Creating, modifying, and assigning IPsec policies.

For more information about IPsec, see IPSec Concepts.

Warning

If you currently have IPsec policies implemented on your network, you must exclude the IP gateways and IP PBXs from the IPsec policy. If you do not, for every 3 seconds of a voice mail there will be a 1 second drop of the voice transmission. This is a known issue and a hotfix for Microsoft Windows Server 2003. For more information about this hotfix, see How to simplify the creation and maintenance of Internet Protocol (IPsec) security filters in Windows Server 2003 and Windows XP.

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UM Dial Plans and VoIP Security in Exchange 2007

Unified Messaging can communicate with IP gateways, IP PBXs, and other Exchange 2007 computers by using encryption. However, this depends on how the UM dial plan has been configured. By default, UM dial plans will not use encryption to protect the VoIP traffic. You can use the Get-UMDialPlan cmdlet in the Exchange Management Shell to determine the security setting for a given UM dial plan. If the VoIP security parameter has been enabled, you can verify that the Microsoft Exchange Unified Messaging service has started in secure mode by checking the application event log to see whether information events numbered 1114 and 1112 have been logged.

By default, Unified Messaging dial plans and the Unified Messaging servers that are associated with the UM dial plan send and receive data by using no encryption. Therefore, they are configured in unsecured mode. In unsecured mode, the VoIP and SIP traffic will not be encrypted. However, the UM dial plans and the Unified Messaging server that are associated with the UM dial plan can be configured by using the VoIPSecurity parameter. The VoIPSecurity parameter configures the dial plan to encrypt the VoIP and SIP traffic by using mutual TLS.

Unified Messaging uses the VoIP protocols Realtime Transport Protocol (RTP) and SIP to communicate with other devices and servers. When you configure the UM dial plan to use VoIP security or secure mode, the SIP signaling channel will be encrypted. The SIP signaling channel can use SIP that is secured by using mutual TLS. However, the media channels that use RTP will still use Transmission Control Protocol (TCP), which is unsecured.

Note

A secure signaling media channel that uses Secure Realtime Transport Protocol (SRTP) will also use mutual TLS to encrypt the VoIP data. SRTP is unavailable in this release of the product. However, SRTP support is planned for a future release. This means that the SIP data and the media channels that are used by Exchange 2007 Unified Messaging will both be encrypted.

After you have created a UM dial plan, you must use the Set-UMDialPlan cmdlet to set the VoIP security mode. When you configure the UM dial plan to use VoIP security, the Unified Messaging servers that are associated with the UM dial plan will use the secure mode or encryption. However, to be able to send encrypted data to and from a Unified Messaging server, you must correctly configure the UM dial plan and devices such as IP gateways or IP PBXs must support mutual TLS.

A Unified Messaging server can be associated with a single or multiple UM dial plans. However, a single Unified Messaging server can use either mutual TLS (secured) or TCP (unsecured), but not both. This is a limitation of the SIP signaling stack. Therefore, a single Unified Messaging server can only be associated with multiple dial plans that have the same security configuration.

By default, when a dial plan is created, it will use unsecured mode or no encryption. However, if you have a Unified Messaging server that is associated with a UM dial plan that has been configured to use mutual TLS to encrypt the VoIP traffic, and you have to disable VoIP security for the dial plan, you must follow these steps:

1. Remove all Unified Messaging servers from the UM dial plan that is currently running in secured mode.

2. Use the Set-UMDialPlan cmdlet to set the dial plan to unsecured mode.

3. Associate the Unified Messaging servers with the dial plan that is now running in unsecured mode.

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How UM Determines Security Mode and Selects Certificates

When the Microsoft Exchange Unified Messaging service starts, it checks the associated UM dial plan and the VoipSecurity parameter setting and identifies whether it should start in a secured or an unsecured mode. If it determines that it must start in a secured mode, it will then determine whether it has access to the required certificates. If the Unified Messaging server is not associated with any UM dial plans, it will determine which mode to start in by looking at the StartSecured parameter in the UMRecyclerConfig.xml file. This parameter can be set with a value of 0 or 1. A value of 1 starts the Unified Messaging server using encryption to protect the VoIP traffic. A value of 0 starts the server, but encryption will not be used to protect the VoIP traffic. If you want to change the startup behavior of the Unified Messaging server from secured to unsecured or from unsecured to secured, you can associate the server with the appropriate UM dial plans and then restart the Unified Messaging server. You can also change the configuration setting in the UMRecyclerConfig.xml configuration file and the restart the Microsoft Exchange Unified Messaging service.

If the Microsoft Exchange Unified Messaging service is started in unsecured mode, it will start correctly. However, make sure that you verify that the IP gateways and IP PBXs are also running in unsecured mode. Also, if you are testing the Unified Messaging server's connectivity in unsecured mode, use the Test-UMConnectivity cmdlet with the -Secured:false parameter.

If the Microsoft Exchange Unified Messaging service is started in secured mode, it will query the local certificate store to find a valid certificate to use for mutual TLS to enable encryption. The service will first look for a valid PKI or commercial certificate and then, if an appropriate certificate is not found, it will look for a self-signed certificate to use. If no PKI, commercial, or self-signed certificate is found, the Microsoft Exchange Unified Messaging service will create a self-signed certificate to use to start in Secure mode. If the Unified Messaging server is starting in unsecured mode, a certificate is not needed.

All the details of the certificate that is used to start in secure mode will be logged whenever a certificate is used or if the certificate has changed. Some details that are logged include the following:

• Issuer Name

• Serial Number

• Thumbprint

The thumbprint is the Secure Hash Algorithm (SHA1) hash and can be used to uniquely identify the certificate that is used. You can then export the certificate that is used by the Microsoft Exchange Unified Messaging service to start in secure mode from the local certificate store and then import this certificate on the IP gateways and IP PBXs on your network into the trusted certificate store.

After an appropriate certificate has been found and is used, and no additional changes have occurred, the Microsoft Exchange Unified Messaging service will log an event one month before the certificate that is being used expires. If you do not make any changes to the certificate during this time, the Microsoft Exchange Unified Messaging service will log an event each day until the certificate expires and each day after the certificate has expired.

When the Unified Messaging server is looking for a certificate to use for mutual TLS to establish an encrypted channel, it will look in the trusted root certificate store. If there are multiple certificates that are valid and are from different issuers, the Unified Messaging server will choose the valid certificate that has the longest time before the certificate will expire. If multiple certificates exist, the Unified Messaging server will choose the certificates based on the issuer and the date that the certificate will expire. The Unified Messaging server will look for a valid certificate in this order.

1. PKI or commercial certificate with the longest expiration period.

2. PKI or commercial certificate with the shortest expiration period.

3. Self signed certificate with the longest expiration period.

4. Self signed certificate with the shortest expiration period.

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Understanding Faxing in Unified Messaging

Microsoft Exchange 2007 Unified Messaging (UM) enables voice mail messages to be delivered into a user's Exchange 2007 mailbox, and also lets users receive fax messages in their Exchange 2007 mailbox. In Exchange 2007 Unified Messaging, a fax message is sent to the user's mailbox as an e-mail message that has an image file with a .tif extension attached. When an e-mail message that has an image attachment is received into their mailbox, a user can open the attached file by using a software application that can open and view image files that have a .tif extension. This topic discusses faxing and how it works in Exchange 2007 Unified Messaging.

Note

Although Unified Messaging does not let users send outgoing faxes, many third-party solutions, such as an Internet fax service, e-mail faxing services, or a third-party fax server application can be used to send outgoing faxes.

Overview of Faxing

Fax is an abbreviation for the word facsimile. It is a technology that is used to electronically transfer documents. Generally, faxes are sent and received by fax machines or computer fax/modems by using the Public Switched Telephone Network (PSTN), a telephony or circuit-based network. However, there are other faxing options that can be used to send and receive faxes.

Almost all organizations today need their users to send and receive faxes. Most organizations use one or more of the methods described in the following list to send or receive faxes over the PSTN or over the Internet. There are advantages and disadvantages to each of these methods.

• Traditional fax machines and computer-based faxing

• Faxing by using fax servers or gateways

• Faxing by using a Voice over IP (VoIP) network

• Faxing by using an e-mail client application

For users in an organization to send a fax message, they may have to do the following:

• Print a hard copy of the document to be faxed and use a physical fax machine to send it.

• Save the document on their computer and use a fax modem to send the fax.

• Use an Internet fax service that lets them fax a document from a software application.

• Send an outgoing fax to a fax server by using a software application that is configured to use the fax server.

For users in an organization to receive a fax, they may have to do the following:

• Receive a fax on a physical fax machine within the organization.

• Receive a fax by using a fax modem that is installed on their computer.

• Receive a fax from an Internet faxing service.

• Receive a fax from a fax server that is configured on a network.

• Receive a fax from a Unified Messaging server on a VoIP network.

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Faxing Methods

There are several options for sending and receiving faxes, including the following:

Traditional fax machines and computer-based faxing   Scanners, a fax modem in a computer, a printer with built-in faxing capabilities, or a dedicated fax machine can be used to send and receive faxes. They are used to transmit data in the form of pulses by using a telephone line to another fax device, usually another fax machine or computer that has a fax modem. The pulses are then transformed into images or used to print the image on paper.

The traditional fax method requires at least a single telephone line on the sending and receiving device, and only one fax can be sent or received at a time. A disadvantage of sending and receiving faxes by using a fax modem is that the computer must be turned on and running fax software or a fax service. This kind of computer-based faxing does not use the Internet to send or receive faxes. The following figure illustrates how traditional and computer-based faxing is used to send and receive faxes.

Traditional and computer-based faxing

Fax servers or gateways and Internet fax services   There are several ways to send and receive faxes over the Internet. These include using a software application on a computer or using an e-mail client to receive faxes. In most cases, this kind of faxing involves using a fax server or fax gateway to convert between faxes and e-mail. This has become increasingly popular because it enables organizations to remove or not purchase additional fax machines. It also eliminates the need to install additional telephone lines. This kind of faxing involves creating the document, including a fax cover page with the correct identifying information, and sending the document to a traditional fax machine. For example, the user uses a software application such as Microsoft Office Word or Microsoft Office Outlook to create and send the fax to the fax server or gateway. The fax server or gateway receives the fax and then sends it by using a traditional telephone line to a fax machine or fax modem that is installed on a computer. The following figure illustrates how fax servers, gateways, and Internet fax services can be used to send and receive faxes.

Faxing by using fax servers or gateways

Internet fax services let a user send faxes from a computer by using the Internet. A software application such as Office Word or Outlook can be used to create and send the fax to an Internet fax service. There are many companies that offer Internet faxing services on a subscription basis or by charging for each fax message that is sent. Internet fax services offer the following advantages:

• No fax machine is required

• No software or hardware must be installed

• No dedicated telephone lines are required

• Confidentiality

• Multiple faxes can be sent at the same time

• Faxes can be received when the computer is shut off

The following figure illustrates how Internet fax services can be used to send and receive faxes.

Internet fax services

Faxing by using an e-mail client application Faxes can be sent and received by a fax machine over the Internet and then received by an e-mail client such as Outlook.

The T.37 protocol was designed to enable a fax machine to send fax messages over the Internet to an e-mail client. The faxes are sent over the Internet as an e-mail attachment, typically as .tif or .pdf files. In this kind of faxing, a fax machine that supports iFax or T.37 is required, in addition to an e-mail address for the sending and receiving fax machines. To work with existing traditional fax machines and fax modems, all T.37 fax machines support standard faxing by using a telephone line. However, in some cases, T.37 fax machines can be used when a fax gateway is also being used. The following figure illustrates how T.37-based fax machines and e-mail clients can be used to send and receive faxes.

Faxing with e-mail

Faxing by using a VoIP network   VoIP is a technology that contains hardware and software that enables people to use an IP-based network as the transmission medium for telephone calls. On a VoIP network, voice and fax data is sent in packets by using IP instead of by traditional circuit transmissions or the circuit-switched telephone lines of the PSTN. An IP gateway that you connect to your IP network uses VoIP to send voice data packets between an Exchange 2007 Unified Messaging server and a Private Branch eXchange (PBX) system. Alternatively, you can use an IP PBX to perform the functions of both an IP gateway and a PBX.

There are two basic types of networks: circuit-switched and packet-switched. A circuit-switched network is a network in which there exists a dedicated connection. A dedicated connection is a circuit or channel that is set up between two nodes so that they can communicate. After a call is established between two nodes, the connection may be used only by these two nodes. When the call is ended by one of the nodes, the connection is canceled. In circuit-switched networks, such as the PSTN, multiple calls are transmitted across the same transmission medium. Frequently, the medium that is used in the PSTN is copper. However, fiber optic cable might also be used.

In packet-switched networks such as the Internet or a local area network (LAN), packets are routed to their destination through the most expedient route, but not all packets traveling between two hosts travel the same route, even those from a single message. This almost guarantees that the packets will arrive at different times and out of order. In a packet-switched network, packets (messages or fragments of messages) are individually routed between nodes over data links that may be shared by other nodes. With packet switching, unlike circuit switching, multiple connections to nodes on the network share the available bandwidth. Packet-switched networking has made it possible for the Internet to exist and, at the same time, has made data networks—especially LAN-based IP and VoIP networks—more available and widespread. The following figure illustrates how a VoIP network and Exchange Unified Messaging can be used to deliver faxes.

Faxing on a VoIP network

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T.38

T.38 is a faxing standard and protocol that enables faxing over an IP-based network. An IP-based network that uses the T.38 protocol uses Simple Mail Transfer Protocol (SMTP) and MIME to send the message to a recipient's mailbox. T.38 allows for IP fax transmissions for IP-enabled fax devices and fax gateways. The devices can include IP network-based hosts such as client computers and printers. In Exchange 2007 Unified Messaging, the fax images are separate documents encoded as .tif files and attached to an e-mail message. Both the e-mail message and the .tif file attachment are sent to the recipient's Exchange 2007 UM-enabled mailbox.

Exchange 2007 Unified Messaging relies on the gateway's abilities to translate or convert Time Division Multiplex (TDM) or telephony circuit-switched based protocols like Integrated Services Digital Network (ISDN) and QSIG from a PBX to IP- or VoIP-based protocols like Session Initiation Protocol (SIP), Real-Time Transport Protocol (RTP), or T.38 for receiving fax messages. The IP gateway is integral to the functionality and operation of Unified Messaging. The IP gateway is responsible for sensing fax tones. Unified Messaging servers rely on the IP gateway to send a notification that a fax has been detected, at which point the Unified Messaging server will renegotiate the media session and use the T.38 protocol.

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Faxing with Unified Messaging

Receiving a fax on a VoIP network differs from receiving a fax on a standard fax machine or by using a fax server that is located on an IP-based network. To enable faxes to be sent and received over a VoIP network, you must have an IP gateway or an IP PBX that supports the T.38 protocol and a server that also supports T.38. T.38 allows for IP-based fax transmissions for IP network-based hosts such as client computers, printers with built-in faxing capabilities, and servers such as a Unified Messaging server.

When a call is received into a PBX, the PBX forwards the call to the appropriate extension. If a ring no answer occurs at the user's extension number, the PBX forwards the call to an IP gateway and the IP gateway forwards the fax call to the appropriate Unified Messaging server. When the call is received by the Unified Messaging server, the Unified Messaging server must decide whether it is a voice call or a fax call. When the SIP protocol is used, the Unified Messaging server processes the call as a voice message. However, if the T.38 protocol is used from the IP gateway, the Unified Messaging server recognizes that the call is for a fax and processes the call. It generates the e-mail message and the .tif attachment, and then submits the fax message to an Exchange 2007 computer that has the Hub Transport server installed that is in the same Active Directory site for delivery to the user's Exchange 2007 mailbox.

By default, when you install the Unified Messaging server role, the server is configured to allow incoming fax calls to be processed and then delivered to a UM-enabled user. However, you can disable the ability for Unified Messaging users to receive faxes by doing any of the following:

• Disabling faxing on a UM dial plan

• Configuring the number of incoming fax calls to 0 on a Unified Messaging server

• Configuring the mailbox for a specific Exchange 2007 user to disable faxing.

For more information about how incoming faxes are sent to a user's mailbox, see Unified Messaging Voice and Fax Call Processing later in this white paper.

In Exchange 2007 Unified Messaging, the user receives the fax images as separate documents encoded as .tif image files that are attached to an e-mail message. Both the e-mail message and the .tif attachment are sent to the recipient's Exchange 2007 UM-enabled mailbox.

There are several advantages to sending a fax message to the user's mailbox. These advantages include the following:

• You can reduce the number of physical or traditional fax machines.

• The number of telephone lines used for faxing in an organization can be reduced, because the Unified Messaging server can queue many faxes and send each fax when one of the telephone lines becomes available.

• Faxes that are received as a .tif image file are better quality than a traditional fax. Incoming faxes can be printed by a local or shared printer.

• Faxes sent to the user's mailbox are more secure because they are less likely than hard copy faxes to be picked up by someone other than the recipient.

• Users can receive faxes without leaving their desk.

• Fax messages that are received can be monitored to make sure that they comply with an organization's security policies.

A single fax message can be sent only to a single UM-enabled user. Exchange 2007 Unified Messaging cannot forward fax messages to a distribution list. If you must have this functionality, you must:

1. Create a mailbox to answer the fax call. This will be the mailbox for the distribution list.

2. UM-enable the distribution list mailbox.

3. Create a rule for this UM-enabled mailbox. The rule will be configured to forward all messages to the chosen distribution list.

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Enabling UM-Enabled Users to Receive Faxes

There are three components that must be configured correctly for users to be able to receive faxes by using Exchange 2007 Unified Messaging. Although, by default, all three of these components allow faxes to be received, you must verify that each setting has been configured correctly. To enable UM-enabled users to receive faxes, you must do the following:

• Verify that each UM dial plan allows the users who are associated with the dial plan to receive faxes. By default, all users who are associated with a dial plan can receive fax messages. To allow UM-enabled users to receive fax messages in their mailbox, each Unified Messaging server that is associated with the dial plan must be configured to accept incoming fax calls. You must also enable fax messages to be received by users who are associated with the dial plan. For more information about how to enable or disable the ability for users to receive faxes for a dial plan, see How to Enable UM-Enabled Users to Receive Faxes.

  Note

  If you prevent fax messages from being received on a dial plan, all users who are associated with the dial plan will be unable to receive fax messages, even if you configure an individual user's properties to allow them to receive fax messages. Enabling or disabling faxing on a UM dial plan takes precedence over the settings for an individual UM-enabled user.

• Verify that the Unified Messaging servers that are associated with the UM dial plan are configured to allow one or more incoming fax calls to be processed. By default, when you install the Unified Messaging server role, the Unified Messaging server will accept 100 concurrent incoming fax calls. This allows UM-enabled users who are associated with a UM dial plan to receive fax messages into their mailbox. However, there may be times when these default settings have changed and UM-enabled users cannot receive fax messages. For more information about how to configure the number of incoming fax calls, see How to Modify the Number of Concurrent Fax Calls Setting.

  You can also prevent all users from receiving fax messages by setting the number of incoming fax calls to 0 on each Unified Messaging server that is associated with a dial plan. If each Unified Messaging server that is associated with a dial plan is configured to receive incoming fax calls but the dial plan is configured to disallow faxing, all users who are associated with the dial plan will be unable to receive faxes. Therefore, the fax settings that are configured on a UM dial plan will take precedence over the fax settings that are configured on a Unified Messaging server.

• Verify that the Exchange 2007 mailbox that is UM-enabled can receive fax messages. By default, all users who are associated with a dial plan can receive faxes. However, there may be situations when a user cannot receive faxes, because the ability to receive faxes has been disabled on their mailbox. For more information about how to enable a UM-enabled user to receive faxes, see How to Enable a Unified Messaging User to Receive Faxes.

  You can prevent a single user who is associated with a dial plan from receiving fax messages. To do this, configure the properties for the user by using the Exchange Management Console or by using the Set-UMMailbox cmdlet in the Exchange Management Shell. You can also use the Set-UMMailbox cmdlet to prevent multiple users from receiving fax messages. For more information about how to prevent a user or users from receiving fax messages, see How to Prevent a Unified Messaging User from Receiving Faxes.

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Faxing Configuration Options

In Exchange 2007 Unified Messaging, you have the following options when you are configuring UM-enabled users to receive fax messages:

• A Direct Inward Dial (DID) telephone number that is used with voice mail.

• A separate DID telephone number that is used for receiving faxes.

• A central fax telephone number that will receive all faxes.

A Single DID Telephone Number

When you enable a user for Unified Messaging by using the Enable Unified Messaging Wizard or by using the Enable-UMMailbox cmdlet, you must specify at least a single extension number for the user. This extension number is enabled on a per-user basis and must be unique within a given dial plan. This extension is used by Unified Messaging to locate the appropriate user in the Active Directory directory service and is used to deliver voice and fax messages into the user's Exchange 2007 mailbox. For more information about the Enable-UMMailbox cmdlet, see Enable-UMMailbox.

In this scenario, the user will use a single DID number for voice and fax. This configuration is easy to administer and does not waste additional DID numbers. If the user is away or on the telephone when a fax call arrives, UM answers the call, detects the fax tone, creates the fax message, and sends it to the user.

However, in this scenario, the user may receive calls from fax machines. The user can:

• Not answer the telephone when it rings, so that the fax call will be forwarded and answered by a Unified Messaging server and the fax message will be created and forwarded to the user's mailbox.

• Answer the fax call, and then transfer it to himself or herself, so that the call will be forwarded and answered by a Unified Messaging server and the fax message will be created and forwarded to the user's mailbox.

• Wait for the caller to retry sending the fax and let the fax call be transferred to a Unified Messaging server.

In summary, using a single DID number requires that the user performs additional actions to be able to receive fax messages.

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Multiple DID Telephone Numbers

When you enable a user for Unified Messaging, you must enter at least a single extension number for that user. However, you can also add multiple extension numbers for a UM-enabled user by using the Set-Mailbox cmdlet SecondaryAddress parameter. For more information about the Set-Mailbox cmdlet, see Set-Mailbox.

Adding multiple extension numbers is useful when a UM-enabled user:

• Receives many faxes

• Does not want to be bothered with answering the telephone to receive a fax

• Does not want to hear a fax tone when they answer their telephone

Adding multiple extensions is more complex than using a single extension, and may require additional configuration settings on a PBX. To configure multiple extension numbers for a UM-enabled user, you must have DID extension numbers that are available but are not being used in your organization. Therefore, it is not a good idea to use multiple numbers for a UM-enabled user if your organization has a limited number of available DID extension numbers. For more information about the IP PBXs and PBXs that are supported by Exchange 2007 Unified Messaging, see IP PBX and PBX Support.

The benefit of using multiple DID telephone numbers is that the UM-enabled user receives voice calls on one DID extension number and fax calls on the other DID extension number. Although, this may be more complex and requires additional configuration steps, using separate DID numbers for voice mail and fax calls is easier for the user.

If you configure two DID extension numbers for a specific user, the DID extension numbers can come from separate UM dial plans. In this scenario, you can create a dial plan, add Unified Messaging servers to the dial plan, and use the Unified Messaging server as a dedicated server that will receive fax calls and forward fax messages to the users. For more information about how to create a UM dial plan, see How to Create a New Unified Messaging Dial Plan.

You have the following options for configuring multiple DID extension numbers for UM-enabled users:

• Multiple DID numbers (one for fax without Unified Messaging and one for voice)   This type of configuration is enabled on a per-user basis and is used when you have extra or unused DID extension numbers available. One DID extension number is published as the user’s voice mail number and the other DID extension number is published as the user's fax number. In this scenario, voice calls that are answered by a ring-no-answer or busy signal are forwarded to a Unified Messaging server, and a voice mail message is created and sent to the UM-enabled user's mailbox. The other extension number can be connected to a fax machine or to another computer that has a fax modem. Although this configuration is possible, it does not require that Unified Messaging servers process the fax calls and fax messages will not be sent to the UM-enabled user's mailbox.

• Multiple DID numbers (one for fax and one for voice)   This type of configuration is enabled on a per-user basis and can be used when your organization has many DID extension numbers available. In this scenario, both DID extension numbers that are answered by a ring-no-answer or a busy signal are forwarded to a Unified Messaging server that will create a voice or fax message depending on the DID extension number that is called. Although the user will publish one number for voice and one for fax, the Unified Messaging server detects the type of call that is being received on the DID extension number and can create a voice or fax message from calls to either of the DID extension numbers. This is very useful when a user does not have a separate fax machine or dedicated computer that has a fax modem to answer incoming fax calls.

• Two DID numbers (one “phantom” extension for fax and one for voice)   This type of configuration is enabled on a per-user basis. It is basically the same as the configuration that uses two DID numbers (one for fax and one for voice). However, in this configuration, the number that is published for fax calls for the UM-enabled user is configured in the PBX as a “phantom” extension. Incoming calls that are received on this "phantom" DID extension number are always forwarded to a Unified Messaging server.

  The advantage of this kind of configuration is that incoming fax calls are answered by a Unified Messaging server. When a ring no answer occurs, a fax is created and forwarded by the Unified Messaging server to the UM-enabled user's mailbox without disturbing the user. This happens because no telephone or fax device is positioned close to the user, and the user does not hear the ring of an incoming call.

  The disadvantages of this kind of configuration are that you must have additional DID extensions available and that you must configure the PBX to forward the call to a Unified Messaging server.

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Central Fax Telephone Number

When you enable a user for Unified Messaging by using the Enable Unified Messaging Wizard or by using the Enable-UMMailbox cmdlet, you must specify at least a single extension number for the user. This kind of fax configuration is defined on each Unified Messaging dial plan.

In some organizations, especially those that receive many faxes each day, you might have to publish one fax number for the whole organization. This fax number would be used by all callers when they submit faxes to users in the organization. This kind of configuration is useful in the following situations:

• A user within the organization receives too many faxes in their mailbox to manage them effectively.

• A user receives too many spam faxes in their mailbox.

• Business logic is too complex to warrant creating a transport rule. This might be the case if your organization requires that you route certain faxes to one group and other faxes to another group. For more information about transport rules, see the following topics:

  • Overview of Transport Rules

  • Understanding How Transport Rules Are Applied in an Exchange 2007 Organization

• Filtering fax messages by using Outlook is not effective.

Publishing one fax number for the whole organization enables your organization to control the types of faxes that are received by users. The advantage of this configuration is that it requires only a single DID extension number or an external telephone number. Also, it does not require a separate DID number for faxing for each UM-enabled user. However, it does require a "fax secretary" or other person to distribute the incoming faxes to users within the organization based on information that is included on the fax cover page or in the fax message itself.

Note

Using a central fax number with optical character recognition (OCR) is not available in Exchange 2007 Unified Messaging. This kind of configuration can use a central fax number. However, instead of having to be routed to the recipient by a person, the faxing software receives the fax, performs OCR, and then tries to locate the recipient based on the information on the cover page or fax message.

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Journaling UM Fax Messages

Many organizations that implement journaling may also use Unified Messaging to consolidate their e-mail, voice mail, and fax infrastructure. However, you may not want the journaling process to generate journal reports for messages that are generated by Unified Messaging. In this case, you can decide whether to journal voice mail messages and missed call notification messages that are handled by an Exchange 2007 Unified Messaging server or to skip such messages. If your organization does not require journaling of such messages, you can reduce the hard disk space that is required to store journal reports by skipping such messages. When you enable or disable the journaling of voice mail messages and missed call notification messages, your change is applied to all Hub Transport servers in your organization. For more information about journaling in Exchange 2007, see Overview of Journaling.

Note

Messages that contain faxes that are generated by a Unified Messaging server are always journaled, even if you configure a journal rule that specifies not to journal Unified Messaging voice mail and missed call notification messages.

Understanding Operator Transfers in Unified Messaging

Microsoft Exchange Server 2007 Unified Messaging includes functionality that enables callers to be transferred to an operator if the caller is unable to correctly navigate the system or must speak to a human operator. There are several types of operators that you can configure. These operators allow callers to be forwarded to the extension number of a receptionist, administrative assistant, operator, or auto attendant instead of the calls being transferred. This topic discusses the different operators that you can configure in Exchange 2007 Unified Messaging and how incoming calls can be transferred to each type of operator depending on how the caller dials into the Unified Messaging system.

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Overview of Operators in Unified Messaging

In Exchange 2007 Unified Messaging, you can configure one or all the following kinds of operators:

• A dial plan operator

• An auto attendant operator

• A personal operator

The following figure illustrates the different types of operators found in Exchange 2007 Unified Messaging.

Unified Messaging operators

With Exchange 2007 Unified Messaging, you have the option to configure an operator extension on UM dial plans, UM auto attendants, and on a UM-enabled user's mailbox. If you have configured an operator extension number on a UM dial plan or on a non-speech enabled UM auto attendant, the caller will hear a voice prompt that says "To reach an operator, press 0". When a caller calls in to a speech-enabled UM auto attendant and an operator extension number is configured, the caller will have the option to press 0 or say "operator" or "reception" and be transferred to an operator extension number.

When you configure an operator extension number for a UM dial plan, auto attendant, or personal operator, you can configure the operator extension number by using one of the following:

• An internal telephone extension number   This can be an extension number for a specific user such as a receptionist, administrative assistant, or another person within the organization that is available to answer the call. Generally, this will be an extension number where a person is always available to answer an incoming call.

• An extension number for a UM auto attendant   This can be used when you want to allow the caller additional menu options before they are transferred to a human operator or when your organization does not have a human operator. In this case, you can configure an extension number that transfers the incoming call to the extension number that is associated with a UM auto attendant. The auto attendant can be either speech-enabled or not speech-enabled.

• An external telephone number   This can be used when a vendor or external answering service is used to answer incoming calls for your organization. If you choose to configure an operator extension number with a telephone number that is external to your organization, you must verify that you have correctly configured your outdialing rules on the UM dial plans and Private Branch eXchanges (PBXs) so that the call transfers will be successful.

At a minimum, we recommended that you configure either the UM dial plan or a UM auto attendant that is associated with the dial plan to have an operator extension number to help callers find the user they are trying to reach or navigate the menu system. For more information about how to configure an operator extension on a UM auto attendant, see How to Configure an Operator Extension on a Unified Messaging Auto Attendant. For more information about how to configure an operator extension number on a UM dial plan, see How to Configure an Operator Extension on a Unified Messaging Dial Plan.

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Dial Plan Operators

Although Exchange 2007 Unified Messaging has many Active Directory objects that must be created and configured during deployment, UM dial plan objects are the central component of the Unified Messaging system. A UM dial plan object is an Exchange 2007 organization-wide object that is created in the Active Directory directory service.

The Unified Messaging dial plan is an Active Directory container object that logically represents sets or groupings of PBXs that share common user extension numbers. In practical terms, user extensions that are hosted on PBXs share a common extension numbering format. Users in the same dial plan can dial one another's telephone extensions without appending a special number to the extension or dialing a full telephone number. Therefore, a UM dial plan is a logical representation of a telephony dial plan that is created on a PBX or IP PBX.

There are two types of callers who will access the Unified Messaging system by using the subscriber access number that is configured on a UM dial plan: unauthenticated callers and authenticated callers. When a caller dials the subscriber access number that is configured on a dial plan, the caller is considered anonymous or unauthenticated until they input information. This information includes their voice mail extension and a PIN. The only option that is available to anonymous or unauthenticated callers is the directory search feature. However, if an operator extension number is configured on the dial plan, the unauthenticated user can use the directory search feature and can also press 0 to be transferred to the operator's extension number that is configured on the dial plan.

After the caller inputs their extension number and their PIN, they will be authenticated and given access to their Exchange 2007 mailbox. After the caller gains access to their mailbox, they will use Outlook Voice Access. Outlook Voice Access is a series of voice prompts that allow the authenticated caller to access their e-mail, voice mail, calendar, and contact information by using a standard analog, digital, or cellular telephone. Outlook Voice Access also enables authenticated callers to navigate their personal information in their mailbox, place calls, locate users, and navigate the system prompts and menus by using dual tone multi-frequency (DTMF) or voice inputs.

When a UM-enabled user uses Outlook Voice Access, they can perform the following tasks:

• Listen to new and saved e-mail and voice mail messages.

• Forward, reply, save, and delete e-mail and voice mail messages.

• Interact with their calendar.

• Locate a person in the global address list (GAL) or personal contacts.

• Send a voice message to a person.

• Change their PIN, spoken name, or greetings.

When an Outlook Voice Access user dials the subscriber access number that is configured on a UM dial plan and an operator extension is configured on the dial plan, when the caller presses the 0 key or says "operator" or "reception", they will be transferred to the telephone number that you have configured on the UM dial plan. If no telephone number is configured for an operator extension on the dial plan, the user will not be given an option to reach an operator and will be politely disconnected from the Unified Messaging system. The following figure illustrates the operator transfer options that are available to an Outlook Voice Access user when they dial in to a subscriber access number.

Operator transfers with Outlook Voice Access

For more information about subscriber access in Exchange 2007 Unified Messaging, see Understanding Unified Messaging Subscriber Access earlier in this white paper.

For a printable copy of the menus and options that are available with Outlook Voice Access, see the Microsoft Download Center for a copy of the Outlook Voice Access Quick Reference Guide.

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Auto Attendant Operators

In Exchange 2007 Unified Messaging, many Active Directory objects must be created and configured during and after deployment. UM auto attendants are not required objects. They are an optional component of the Unified Messaging system that you can configure. A UM auto attendant object is an Exchange 2007 organization-wide object that is created in Active Directory.

Exchange 2007 Unified Messaging enables you to create one or more UM auto attendants, depending on the needs of your organization. UM auto attendants can be used to create a voice menu system for an organization. This voice menu system lets external and internal callers locate users in an organization and place or transfer calls to users, departments, or to an operator extension number that has been configured on the UM auto attendant.

You can configure an operator extension number on speech-enabled and non-speech enabled UM auto attendants. Configuring an operator extension number on a UM auto attendant allows callers to press 0 or say "operator" or "receptionist" to transfer to a human operator or another auto attendant if they cannot navigate the auto attendant menu. There are three types of UM auto attendants that you can configure to use an operator extension number:

• A non-speech enabled auto attendant

• A speech-enabled auto attendant that does not have a DTMF fallback

• A speech-enabled auto attendant that has a DTMF fallback

You can configure the operator extension number on a UM auto attendant to be the extension number of a human operator, another auto attendant, a UM-enabled mailbox, or a telephone number that is external to an organization. An internal or external telephone number from 1 to 20 digits can be entered for the operator's extension number. If you use an external telephone number, you must verify that you have correctly configured the appropriate outdialing rule groups and entries to enable this functionality. For more information about how to configure outdialing entries, see How to Create a Dialing Rule Entry on a Unified Messaging Dial Plan.

If you have created a speech-enabled auto attendant and have configured an operator extension on the speech-enabled auto attendant, when the caller says "operator", the auto attendant will forward the call to the number that is configured on the speech-enabled auto attendant. If the speech-enabled auto attendant is configured to have a DTMF fallback auto attendant but not to have an operator extension number and the DTMF auto attendant is configured to have an operator extension number, the operator extension number on the DTMF fallback auto attendant will be dialed. If no extension number is configured on the speech-enabled auto attendant or the DTMF fallback auto attendant and the caller says "operator", the system will call the operator extension that is configured on the dial plan that is associated with the auto attendant. If neither of the auto attendants or the dial plan is configured to have an operator extension, the system will respond by saying "Sorry. Neither the operator or the touchtone service are available".

Note

At a minimum, we recommend that you configure either the auto attendant or the dial plan that is associated with the auto attendant to have an operator extension number to help callers.

For UM auto attendants, you can configure business hours operator transfers on the properties for the UM auto attendant. However, by default, business hours transfers are enabled. You can also configure non-business hours operator transfers on the UM auto attendant. However, by default, the business hours for a UM auto attendant are 24 hours a day. This means that non-business hours or after hours operator transfers will not be available. To configure operator transfers after business hours, you must first configure the business hours schedule on the UM auto attendant properties and then enable or disable operator transfers during business or non-business or hours.

• For more information about how to configure the business hours for a UM auto attendant, see How to Configure Business Hours for a Unified Messaging Auto Attendant.

• For more information about how to enable or disable operator transfers after business hours, see How to Enable or Disable Operator Transfers After Business Hours on a Unified Messaging Auto Attendant.

• For more information about how to enable or disable operator transfers during business hours, see How to Enable or Disable Operator Transfers During Business Hours on a Unified Messaging Auto Attendant.

The following figure illustrates the operator transfer options that are available to a caller when they dial in to a UM auto attendant that is not speech-enabled. For more information about how to create a UM auto attendant, see How to Create a New Unified Messaging Auto Attendant.

Auto attendant that is not speech-enabled

The following figure illustrates the operator transfer options that are available to a caller when they dial in to a UM auto attendant that is speech-enabled but does not have a DTMF fallback auto attendant configured. For more information about how to speech-enable a UM auto attendant, see How to Speech-Enable a Unified Messaging Auto Attendant.

Speech-enabled auto attendant without a DTMF fallback auto attendant

The following figure illustrates the operator transfer options that are available to a caller when they dial in to a UM auto attendant that is speech-enabled and also has a DTMF fallback auto attendant configured. For more information about how to configure a UM auto attendant that has a DTMF fallback auto attendant, see How to Configure a Unified Messaging Auto Attendant with a DTMF Fallback Auto Attendant.

Speech-enabled auto attendant with a DTMF fallback auto attendant

Although UM auto attendants are an optional feature that can be created and configured when you are deploying Unified Messaging, we recommended that, if you make the choice to create and configure a single UM auto attendant or multiple auto attendants, you take the time to plan them carefully. One of the most important factors when planning for auto attendants is to make sure that callers can contact a human operator or another auto attendant to correctly direct their calls. If you do not plan and implement the auto attendants for your organization correctly, the system could frustrate callers enough that they will not call in to the system again.

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Personal Operators

Exchange 2007 Unified Messaging enables you to configure a personal operator extension number on a user's UM-enabled mailbox. As the administrator, you can configure a personal operator for a UM-enabled user. However, the UM-enabled user will be unable to configure this setting. If the UM-enabled user were to have access to configure this setting, they could potentially forward all their calls to another UM-enabled user or to an internal extension number that is not valid. This could be very frustrating for the user to whom the calls were being forwarded for callers. Callers would be unable to leave a voice message for the UM-enabled user they were trying to contact and could lose their place in the menu system, and eventually give up without reaching the user they were trying to contact.

The personal operator extension setting on a UM-enabled user's mailbox can be used when an administrative assistant or personal assistant will answer incoming calls for a specific user instead of a voice mail being generated for the user. By default, a personal operator extension number is not defined.

For a caller to be transferred to a personal operator, the caller must enter 0 on the telephone keypad when the user's custom voice mail message greeting is being played. Therefore, we recommended that, if a user is going to use a personal operator, they include information in their custom voice mail greeting to give the caller instructions about how to access their personal operator.

However, if the user has not configured a customized voice mail greeting, the default system greeting will be used and the system will add the operator prompt automatically. For example, "Please leave a message for Tony Smith. To speak to an administrative assistant and leave a message, press 0". If the caller does not press 0 during the voice mail greeting, the caller will be able to leave a voice message for the user.

If you have not configured a personal operator extension for a UM-enabled user's mailbox, the Unified Messaging server will use the operator extension number that is configured on the UM auto attendant or UM dial plan, depending on which number the caller has called. If the caller has called an auto attendant telephone extension number, they will be forwarded to the operator, if one has been configured on the UM auto attendant. If they have called the subscriber access number that is configured on a UM dial plan, the caller will be forwarded to the operator extension number that is configured on the UM dial plan. If an operator extension has not been configured, the caller will be politely disconnected from the system. For more information about how to configure a personal operator, see How to Configure a Personal Operator for a UM-Enabled User.

In most cases, an internal extension number for an administrative assistant, receptionist, or operator will be configured as a personal operator. A personal operator extension number can be configured as an internal or external telephone number that ranges from 1 to 20 digits. However, if you use an external telephone number, you must verify that you have correctly configured the appropriate outdialing rule groups and entries to enable this functionality. For more information about how to configure outdialing entries, see How to Create a Dialing Rule Entry on a Unified Messaging Dial Plan.

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Understanding Outdialing

There are many outdialing settings that are used on a Microsoft Exchange Server 2007 Unified Messaging server to dial internal and external calls for users. To configure outdialing, you must configure dialing rule groups, dialing rule entries, and dialing restrictions on UM dial plans and UM mailbox policies. Additionally, you can also configure UM dial plans to have dialing or access codes, a national number prefix, and in-country/region or international number formats that enable you to control outdialing in your organization. This topic discusses dialing rule groups, dialing rule entries, and dialing restrictions and how they are used to control outdialing for your organization.

Overview of Unified Messaging Outdialing

Outdialing is the process that is used by users when they call in to a UM dial plan or UM auto attendant and place or transfer a call to an internal or external telephone number. When a user calls in to a UM dial plan or a UM auto attendant and places a call, a Unified Messaging server will use the settings that are configured on the dial plan, auto attendant, and if appropriate, the UM mailbox policy to place the call. The outdialing process happens when:

• A Unified Messaging server places a call to an external telephone number for a caller.

• A Unified Messaging server transfers a call to an auto attendant.

• A Unified Messaging server transfers a call to a user in your organization who is UM-enabled or not UM-enabled.

• A UM-enabled user uses the Play on Phone feature that is found in Microsoft Office Outlook 2007 or Outlook Web Access in Exchange 2007.

There are two types of users who can use the outdialing feature in Unified Messaging: authenticated and unauthenticated. The users who call in to a subscriber access number that is configured on a UM dial plan are unauthenticated at first. All users who call in to a UM auto attendant are unauthenticated. When a user calls in to a subscriber access number, they are considered unauthenticated because they have not provided their extension number and PIN and logged on to their Exchange 2007 mailbox. The following figure illustrates the outdialing process for an unauthenticated user.

Outdialing process for an unauthenticated user

Users are authenticated after they provide their extension number and PIN and successfully log on to their Exchange 2007 mailbox. The following figure illustrates the outdialing process for a user who has been authenticated.

Outdialing process for an authenticated user

When a user calls in to a subscriber access number that is configured on a UM dial plan and tries to place or transfer a call without logging on to their Exchange 2007 mailbox, only the UM dial plan outdialing settings will apply to the call. The user is unauthenticated because they did not log on to their mailbox. However, when an anonymous or unauthenticated user calls in to a UM auto attendant, both the outdialing settings that are configured on the auto attendant and the outdialing settings that are configured on the dial plan that is associated with the auto attendant are applied to the call.

When a user calls in to the subscriber access number that is configured on a dial plan and successfully logs on to their Exchange 2007 mailbox, they become an authenticated user. The configuration settings from the UM dial plan and the UM mailbox policy that is associated with the authenticated user are both applied to any outdialing calls the user makes.

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Outdialing Settings

There are several settings that you must configure to apply outdialing rules for your organization. To control outdialing, you must configure the UM dial plans, UM auto attendants, and UM mailbox policies that you have created. The following outdialing settings are configured on dial plans, auto attendants, and UM mailbox policies:

• Outside line, country/region, and international access codes

• National number prefixes

• In-country/region and international number formats

• Configured in-country/region and international dialing rule groups

• Allowed in-country/region and international dialing rule groups

• Dialing rule entries

• Dialing restrictions

For you to successfully configure outdialing for your Exchange 2007 organization, you must first understand how each component can be used with outdialing and how they must be configured. The following table introduces each component that must be configured on UM dial plans, UM auto attendants, and UM mailbox policies to enable outdialing to function correctly.

Outdialing components

Component	Description
Dial codes, number prefixes, and number formats	Dial codes, number prefixes, and number formats are used by a Unified Messaging server to determine the correct number to dial when placing an outgoing call. You can configure dial codes, number prefixes, and number formats to restrict outgoing calls for users who dial in to a UM auto attendant that is associated with a UM dial plan or for users who dial in to the subscriber access number that is configured on the dial plan. For more information about dial codes, number prefixes, and number formats, see Understanding Dial Codes, Number Prefixes, and Number Formats later in this white paper.
Dialing rule groups	Dialing rule groups are created to enable telephones to be modified before they are sent to the Private Branch eXchange (PBX) for outgoing calls. Dialing rule groups remove numbers from or add numbers to telephone numbers that are being placed by a Unified Messaging server. For example, you can create a dialing rule group that automatically adds a 9 as a prefix to a 7-digit telephone number to provide access to an outside line. In this example, users who place outgoing calls will not have to dial the 9 before the telephone number to reach someone external to the organization. Each dialing rule group contains dialing rule entries that determine the types of in-country/region and international calls that users within a dialing rule group can make. Dialing rule groups apply to the users who are associated with a UM dial plan or UM auto attendants and UM mailbox policies that are associated with the UM dial plan. Each dialing group rule must contain at least one dialing rule entry.
Dialing rule entries	A dialing rule entry is used to determine the types of calls that users within a dialing rule group can make. When you create a dialing rule group, you configure one or more dialing rule entries. When you configure each dialing rule entry, you must enter the name, number mask, and dialed number. You can also enter a comment. Comments can be used to describe how the dialing rule entry will be used or to describe a group of users to whom the dialing rule entry will apply. When you add a number mask and the dialed number to a dialing rule entry, you can substitute the letter x to replace a digit in a telephone number, for example, 91425xxxxxxx. You can also use an asterisk (*) symbol as a wildcard character, for example, 91425*.
Dialing restrictions	A dialing restriction uses dialing rule groups to apply dialing restrictions for users who are associated with a given UM mailbox policy. They can also be used when you want to let users place calls to in-country/region or international telephone numbers. After you create a dialing rule group on a UM dial plan, you add the dialing rule group to a UM mailbox policy. After the dialing rule group is added to a UM mailbox policy, all settings or rules that are defined will apply to UM-enabled users who are associated with the UM mailbox policy.

We recommend that you follow the steps in the following figure when you configure outdialing on your dial plans, auto attendants, and UM mailbox policies, to ensure that outdialing will function correctly.

Configuring outdialing

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Configuring Outdialing

A dialing rule group is a collection of one or more dialing rule entries that are configured on a UM dial plan. There are two types of dialing rule groups that can be configured on a UM dial plan: in-country/region and international. In-country/ region dialing rule groups apply to telephone numbers that are dialed within the same country or region. International dialing rule groups apply to international telephone numbers that are dialed from one country or region to another country or region.

Each UM dial plan can contain one or more dialing rule groups. However, to apply a dialing rule group to a set of users, after you create the dialing rule group, you must add the configured dialing rule group to the list of allowed dialing rule groups that are on the UM dial plan and on the UM auto attendants and UM mailbox policies that are associated with the UM dial plan.

Dialing rule groups enable administrators to specify dialing rule entries that they want to apply to a group of UM-enabled users who fall into a specific category. For example, you can use dialing rule groups to specify which group of users can place international calls and which group can only make in-state or local calls. You can create a dialing rule group by using the Exchange Management Console or the Set-UMDialPlan cmdlet in the Exchange Management Shell. When you create a dialing rule group, you must define at least one dialing rule entry for the dialing rule group.

When a number is dialed by a user, the Unified Messaging server takes the telephone number and looks for a match in the dialing rule entries. If a match is found, the dialing rule entry that is configured on the dialing rule group will be applied. The Unified Messaging server looks at the dialing rule entry to determine the number to dial by looking at the telephone number or digits that are listed in the "DialedNumber" section of the dialing rule entry. The number that is listed in the "DialedNumber" section of the dialing rule entry will be dialed by the Unified Messaging server.

The following table shows an example of dialing rule groups and dialing rule entries. In this example, "Local-Calls-Only" and "Low-Rate" are the dialing rule groups that have been created. For each dialing rule group, "Local-Calls-Only" and "Low-Rate", there are two dialing rule entries: 91425* and 91206* and 91509* and 91360*, respectively.

Dialing rule groups and dialing rule entries

Name	NumberMask	DialedNumber	Comment
Local-Calls-Only	91425*	91*	Local calls
Local-Calls-Only	91206*	91*	Local calls
Low-Rate	91509*	9*	In-state calls
Low-Rate	91360*	9*	In-state calls

For example, when a user dials 9-1-425-555-1234, the telephone number that the Unified Messaging server dials is 4255551234. The Unified Messaging server will remove any non-numeric characters (in this example, the hyphens) and apply the number mask from the dialing rule entry. In this example, the Unified Messaging server will apply the number mask 91*. This tells the Unified Messaging server not to dial the 9 or the 1, but to dial all the other numbers in the telephone number that appear to the right of the number 1. This includes all the numbers that are represented by the asterisk (*).

You can use the Exchange Management Console or the Exchange Management Shell to create and configure single or multiple in-country/region and international dialing rule groups and dialing rule entries. However, if you are creating many or complex dialing rule groups and dialing rule entries, you can use a comma-separated value (.csv) file in the Exchange Management Shell. You can import or export a list of dialing rule groups and dialing rule entries.

To import a list of dialing rule groups and dialing rule entries that you have defined in a .csv file, run the Set-UMDialPlan cmdlet, as follows:

Set-UMDialPlan "MyUMDialPlan" -ConfiguredInCountryOrRegionGroups $(IMPORT-CSV c:\dialrules\InCountryRegion.csv)

To retrieve a list of the dialing rule groups that are configured on a UM dial plan, run the Get-UMDialPlan cmdlet, as follows:

(Get-UMDialPlan -id "MyUMDialPlan").ConfiguredInCountryOrRegionGroups | EXPORT-CSV C:\incountryorregion.csv

The .csv file must be created and saved in the correct format for the file to be used. Each line in the .csv file represents one dialing rule entry. However, each dialing rule entry is configured on the same dialing rule group. Each entry in the file will have four sections that are all separated by commas. These sections are name, number mask, dialed number, and comment. Each section is required and you must enter the correct information in each section except for the comment section. There should be no spaces between the text entry and the comma for the next section, nor should there be any blank lines in between entries or at the end. The following is an example of a .csv file that can be used to create in-country/region dialing rule groups and dialing rule entries:

Name,NumberMask,DialedNumber,Comment

Low-rate,91425xxxxxxx,9xxxxxxx,Local call

Low-rate,9425xxxxxxx,9xxxxxxx,Local call

Low-rate,9xxxxxxx,9xxxxxxx,Local call

Any,91*,91*,Open access to in-country/region numbers

Long-distance,91408*,91408*,long distance

The following is an example of a .csv file that can be used to create international dialing rule groups and dialing rule entries:

Name,NumberMask,DialedNumber,Comment

International, 901144*, 901144*, international call

International, 901133*, 901133*, international call

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Applying Configured Dialing Rule Groups

Dialing rule groups are created on a UM dial plan. You can create in-country/region or international dialing rule groups by using the Exchange Management Console or the Set-UMDialPlan cmdlet in the Exchange Management Shell. After you create the appropriate dialing rule groups on a UM dial plan and define the dialing rule entries, you can apply the dialing rule groups that you created to a UM dial plan, a UM auto attendant, or to users who are associated with a UM mailbox policy, depending on how the user accesses the Unified Messaging system.

You can apply the dialing rule groups that you created on a UM dial plan to the following:

• The same dial plan   The settings will apply to all users who call in to the subscriber access number but do not log on to their Exchange 2007 mailbox. To apply an in-country/region dialing rule group named "MyAllowedDialRuleGroup" to the same dial plan, use the Exchange Management Shell Set-UMDialPlan cmdlet, as follows.

  Set-UMDialPlan -Identity MyUMDialPlan -AllowedInCountryOrRegionGroups MyAllowedDialRuleGroup
  

• A single or multiple UM mailbox policies   The settings that are configured on a UM mailbox policy will apply to all users who are associated with a given UM mailbox policy. The settings that are configured on a UM mailbox policy apply to users who call in to a subscriber access number and log on to their Exchange 2007 mailbox. To apply an in-country/region dialing rule group named "MyAllowedDialRuleGroup" to a single UM mailbox policy, use the Dialing Restrictions tab in the Exchange Management Console or use the Exchange Management Shell Set-UMMailboxPolicy cmdlet, as follows.

  Set-UMMailboxPolicy -Identity MyUMMailboxPolicy --AllowedInCountryOrRegionGroups MyAllowedDialRuleGroup
  

• Single or multiple auto attendants that are associated with the UM dial plan   This will apply to all users who call in to a UM auto attendant. To apply the in-country/region dialing rule group named "MyAllowedDialRuleGroup" to a single UM auto attendant, use the Exchange Management Shell Set-UMAutoAttendant cmdlet, as follows.

  Set-UMAutoAttendant -Identity MyUMAutoAttendant -AllowedInCountryOrRegionGroups MyAllowedDialRuleGroup
  

The following table summarizes the way that dialing rule groups are applied in Unified Messaging.

Applying outdialing rules

Caller Type	Scope	Outdialing settings applied
Subscriber access or Outlook Voice Access	User calls a dial plan subscriber access number and logs on to their mailbox	UM mailbox policy
Anonymous caller	User calls a dial plan subscriber access number	UM dial plan
Anonymous caller	User calls an auto attendant pilot number	UM auto attendant
Caller from inside the organization	User calls the Play on Phone number	UM mailbox policy

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Applying Dialing Rules

The outdialing process happens when:

• A Unified Messaging server places a call to an external telephone number for a caller.

• A Unified Messaging server transfers a call to an auto attendant.

• A Unified Messaging server transfers a call to a user in your organization who is UM-enabled or not UM-enabled.

• A UM-enabled user uses the Play on Phone feature that is found in Microsoft Office Outlook 2007 or Outlook Web Access in Exchange 2007.

In each outdialing scenario, a Unified Messaging server will apply the outdialing rules that have been configured, and then place the call for the user. However, depending on the scenario and how the call is initiated by the user, a Unified Messaging server may apply only some of the outdialing rules to the telephone number that is being dialed. In other outdialing scenarios, the Unified Messaging server may apply all the outdialing rules that are configured to the telephone number that is being dialed. The outdialing rules that are applied based on how the call was initiated are illustrated in the following figures.

The following figure illustrates how outdialing rules are applied when a user uses the Play on Phone feature to place a call.

Play on Phone outdialing

The following figure illustrates how outdialing rules are applied when a user places a call to a personal contact.

Dialing a personal contact

The following figure illustrates how outdialing rules are applied when a user who is enabled for Unified Messaging places a call to another UM-enabled user.

Outdialing for a UM-enabled user

The following figure illustrates how outdialing rules are applied when a user who is UM-enabled places a call to a user who is not enabled for UM.

Outdialing for a user who is not UM-enabled

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Understanding Dial Codes, Number Prefixes, and Number Formats

You can configure several dialing codes that are used by a Unified Messaging server to dial internal and external calls for UM-enabled users. Frequently, you will want to configure a dial plan together with the dialing or access codes, a national number prefix, or the in-country/region or international number formats so that you can control outdialing for users in your organization. This topic discusses dial codes, number prefixes, and number formats and how you can use them to control outdialing for your organization.

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Overview

Outdialing is the process that is used by users when they call in to a UM dial plan or UM auto attendant and then place a call to an internal or external telephone number. When a user calls in to a UM dial plan or a UM auto attendant and then places a call, a Unified Messaging server uses the settings that are configured on the dial plan, auto attendant, and UM mailbox policies to place the call. A Unified Messaging server will place an outgoing call in the following situations:

• When it places a call to an external telephone number for a caller.

• When it transfers a call to an auto attendant.

• When it transfers a call to a user in your organization who is enabled for Unified Messaging or not enabled for Unified Messaging.

• When a UM-enabled user uses the Play on Phone feature in Microsoft Office Outlook 2007 or the version of Outlook Web Access that released with Microsoft Exchange Server 2007.

There are two types of users who use outdialing: authenticated and unauthenticated. Unauthenticated users are users who call in to a subscriber access number that is configured on a UM dial plan but do not log on to their mailbox and users who call in to a number that is configured on a UM auto attendant. Authenticated users are users who call in to a subscriber access number and successfully log on to their Exchange 2007 mailbox. When a user calls in to a subscriber access number, they are considered unauthenticated because they have not provided their extension number and PIN and logged on to their mailbox. They are authenticated after they provide their extension number and PIN and successfully log on to their Exchange 2007 mailbox.

When an unauthenticated user calls in to a UM auto attendant and places a call by using outdialing, the outdialing settings that are configured on the UM dial plan and the auto attendant are used. When an unauthenticated user calls in to a subscriber access number that is configured on a dial plan, the settings that are configured on the dial plan are the only settings that will be used. However, when a user has successfully logged on to their Exchange 2007 mailbox, configuration settings from the dial plan and the UM mailbox policy that are associated with the authenticated user are applied to the authenticated user.

There are several settings that you must configure to control outdialing for your organization. To control outdialing you must configure the UM dial plans, auto attendants, and UM mailbox policies in Exchange 2007 Unified Messaging. The following settings can be configured on UM dial plans, auto attendants, and UM mailbox policies to control outdialing:

• Outside line, country/region, and international access codes

• National number prefixes

• In-country/region and international number formats

• In-country/region and international dialing rule groups

• Allowed in-country/region and international dialing rule groups

• Dialing rule entries

You configure access codes, number prefixes, and number formats on a UM dial plan on the Dial Codes tab in the Exchange Management Console. You can also configure them by using the Set-UMDialPlan cmdlet. You can choose to configure all the settings, none of the settings, or only some of the settings. However, each setting controls a specific part of the outdialing process.

Access codes, number prefixes, and number formats are used by a Unified Messaging server to determine the correct number to dial and can be configured to restrict outgoing calls for users who dial in to a UM auto attendant that is associated with a UM dial plan or when a user dials in to the subscriber access number that is configured on the dial plan. The following figure illustrates the outdialing process and how access codes can be used to control outdialing.

Outdialing overview

For more information about outdialing in Unified Messaging, see Understanding Outdialing earlier in this white paper.

For more information about how to configure outdialing, see Managing Outdialing.

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Outside Line Access Code

An outside line access code should be configured on each dial plan that you create. However, this depends on the type of telephony network that you have and how it is configured. You can configure an outside line access code, also known as a "trunk access code", on each dial plan that you create. This is the number that is used to gain access to an outside telephone line. This number is also configured on the Private Branch eXchanges (PBXs) or IP PBXs in your organization. In most telephony networks, users dial the number 9 to gain access to an outside line and place a call to an external telephone number.

If you do not configure the outgoing dial codes on a dial plan, when a Unified Messaging server that is associated with the dial plan dials an outgoing call, the PBX or IP PBX may be unable to recognize the number string that is sent. If this happens, the PBX or IP PBX will be unable to complete the outgoing call for the user. For example, as stated earlier, in many organizations the access code that users dial to gain access to an outside line is 9, and this is configured on a PBX or IP PBX. The Unified Messaging server must prepend the number 9 to the telephone number string for the PBX or IP PBX to correctly dial the outgoing number. If you configure the dialing code so that the Unified Messaging server will prepend the outside line access code, the Unified Messaging server will be able use the outside line access code gain access to an outside line before it dials the external telephone number string. The dialing code that you configure will apply to all users who are associated with a UM mailbox policy that is associated with the UM dial plan.

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National Number Prefix

The national number prefix and the country/region code can also be configured on a UM dial plan. The national number prefix is used by the Unified Messaging server to dial the correct national number prefix or country/region code when a user dials an outgoing call that is destined within the same country/region or is an international call. For example, when a user places an outgoing international call to Europe, the Unified Messaging server will prepend the national number prefix to the number string that it sends to the PBX to place the outgoing call. The Unified Messaging server will prepend the number 0 for Europe to the telephone number string. The number 1 is used as the national number prefix for North America.

Country/Region Access Code

A country/region access code can be configured on a UM dial plan. The country/region access code consists of the digits that are associated with a specific country or region. The country/region access code is used by the Unified Messaging server to dial the correct telephone number when a call is placed to a telephone number from inside the same country or region. The Unified Messaging server will prepend this number to the number string that it sends to the PBX or IP PBX when it places the outgoing call. For example, the Unified Messaging server will prepend the number 1 to a call that is placed from the United States and is destined for the United States. For the United Kingdom, the country/region code is 44.

International Access Code

An international access code can be configured on a UM dial plan. The international access code consists of the digits that are used to access international telephone numbers. The international access code is used by the Unified Messaging server to dial the correct international access code when a call is placed from a telephone number within a country/region but the number being dialed is located in another country/region. The Unified Messaging server will prepend this number to the number string that it sends to the PBX or IP PBX when it places the outgoing call. For example, the Unified Messaging server will use 011 as the international access code for the United States. For Europe, the international access code is 00.

In-Country/Region and International Number Formats

You can configure the incoming call configuration for in-country/region and international number formats on a UM dial plan. After you configure these settings, the Unified Messaging server will be able to recognize incoming calls from inside a country/region and internationally from other UM dial plans within the same Exchange 2007 organization. Configuring these options also enables your organization to save money by preventing outgoing calls that should not be made by users from inside your organization and helps prevent toll fraud. The Unified Messaging server will use the information that you configure to match the number format of the incoming call and verify that the number pattern matches before it accepts the call. For example, you may have multiple dial plans inside an organization that exist within the same Active Directory forest. If you have one dial plan for the United States and another for the United Kingdom, you may want to let users in the United States dial plan have Unified Messaging servers place calls to users who are located in the United Kingdom dial plan but not let the users in the United States dial plan place calls directly to other country/regions or internationally.

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Overview of Unified Messaging Active Directory Objects

Active Directory objects are required for the deployment and operation of Microsoft Exchange Server 2007 Unified Messaging (UM). The Active Directory UM objects connect the telephony infrastructure and the Exchange Server 2007 Unified Messaging Active Directory environment.

UM Active Directory Objects

The UM Active Directory objects enable the integration of Exchange Server 2007 Unified Messaging into the Active Directory directory service and the existing telephony infrastructure. Active Directory acts as a container for all the UM objects that are created and their configuration settings. Each UM object within Exchange Server 2007 is necessary to support Unified Messaging in an Active Directory environment. Some UM Active Directory objects are created to logically represent a telephony hardware device whereas others are created to represent a telephony dial plan for an organization or to support a specific feature of Exchange Server 2007 Unified Messaging. The following figure illustrates the relationships between the Unified Messaging objects that are found in Active Directory.

The relationships between UM Active Directory objects

• There exists a tightly integrated and interconnected relationship between the UM Active Directory objects and the features that are available in Exchange Server 2007 Unified Messaging. In order to successfully plan and deploy Exchange Server 2007 Unified Messaging in your organization you must fully understand this logical relationship between each of the UM objects.

For more information about the UM Active Directory objects, see the following sections later in this white paper:

• Understanding Unified Messaging Dial Plans

• Understanding Unified Messaging Mailbox Policies

• Understanding Unified Messaging IP Gateways

• Understanding Unified Messaging Hunt Groups

• Understanding Unified Messaging Auto Attendants

• Understanding Unified Messaging Servers

• Understanding Unified Messaging Users

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Understanding Unified Messaging Dial Plans

Unified Messaging dial plans are integral to the operation of Microsoft Exchange Server 2007 Unified Messaging and are required to successfully deploy Unified Messaging on your network. The following sections discuss Unified Messaging dial plans and how UM dial plans are used when you deploy Exchange 2007 Unified Messaging on your network.

Overview of Unified Messaging Dial Plans

Although Exchange 2007 Unified Messaging has many Active Directory objects that must be created and configured during deployment, UM dial plan objects are the central component of the Unified Messaging system. A UM dial plan object is an Exchange 2007 organization-wide object that is created in Active Directory.

The Unified Messaging dial plan is an Active Directory container object that logically represents sets or groupings of Private Branch eXchanges (PBXs) that share common user extension numbers. In practical terms, users' extensions that are hosted on PBXs share a common extension number. Users can dial one another’s telephone extensions without appending a special number to the extension or dialing a full telephone number. A UM dial plan is a logical representation of a telephony dial plan.

Note

A telephony dial plan is configured on a legacy PBX or IP PBX.

For more information about telephony components, see Unified Messaging Telephony Concepts and Components earlier in this white paper.

In Exchange 2007 Unified Messaging, the following UM dial plan topologies can exist:

• A single dial plan that represents a subset of extensions or all extensions for an organization that has one PBX.

• A single dial plan that represents a subset of extensions or all extensions for an organization that has multiple networked PBXs.

• Multiple dial plans that represent a subset of extensions or all extensions for an organization that has one PBX.

• Multiple dial plans that represent a subset of extensions or all extensions for an organization that has multiple PBXs.

Users who belong to the same dial plan have the following characteristics:

• An extension number that uniquely identifies the user mailbox in the dial plan.

• The ability to call or send voice messages to other members in the dial plan by using only the extension number.

For more information about how to enable a user for Unified Messaging, see How to Enable a User for Unified Messaging.

UM dial plans are implemented in Exchange 2007 Unified Messaging to make sure that user telephone extensions are unique. In some telephony networks, multiple PBXs can exist. In these telephony networks, there could be two users in Active Directory who have identical telephone extensions. UM dial plans resolve this situation. You can put the two users into two separate UM dial plans. This makes their extensions unique.

Note

A user can be a member of only one UM dial plan. You can also use a UM dial plan to establish a common set of policies for a group of users. For example, you can enable different languages for different UM dial plans, or you can enable different features for different UM dial plans.

The following figure illustrates how Unified Messaging dial plans can be used in an organization that has a single forest and multiple physical sites.

UM dial plans in a single forest in an organization that has multiple physical sites

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How Dial Plans Work

When you integrate a telephony network together with Exchange 2007 Unified Messaging, there must be a hardware device called an IP gateway that connects your telephony network together with your IP-based network. IP gateways convert circuit-switched protocols that are found in a telephony network to a data-switched protocol such as IP. Each IP gateway in your organization is represented by a Unified Messaging IP gateway in Active Directory. For more information about UM IP gateways, see Understanding Unified Messaging IP Gateways later in this white paper.

Exchange 2007 Unified Messaging requires that you create at least one UM dial plan and that the UM dial plan has a UM server and a UM IP gateway associated with it. After you install the Unified Messaging server role on a computer that is running Exchange 2007, you must associate the UM server together with at least one UM dial plan. You can also associate a single UM server with multiple UM dial plans. After the UM server is associated with a UM dial plan, you must create a UM IP gateway and associate it to the UM dial plan that was created.

Important

Each time that you create a UM dial plan, a UM mailbox policy will also be created. The UM mailbox policy will be named <Dial Plan Name> Default Policy.

When you create the first UM IP gateway and specify a UM dial plan at the time that you create it, a default UM hunt group is also created. Creating and associating these objects in Active Directory enables the Unified Messaging server to receive calls from the IP gateway and then process incoming calls for users who are associated with the UM dial plan. When a call comes in to the IP gateway, it forwards the call to a UM server and the Unified Messaging server tries to match the extension number of the user to the associated UM dial plan.

Note

A default UM mailbox policy is created after you create the first UM dial plan.

For more information about how to add a Unified Messaging server to a UM dial plan, see How to Add a Unified Messaging Server to a Dial Plan.

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Types of Dial Plans

A Uniform Resource Identifier (URI) is a string of characters that is used to identify or name a resource. In Unified Messaging, the main purpose of a URI is to enable Voice over IP (VoIP) devices to communicate with other devices by using specific protocols. A URI defines the naming and numbering format or scheme that is used for the calling and called party information that is contained within a Session Initiation Protocol (SIP) header for an incoming or outgoing call.

The types of UM dial plans that you create in Exchange 2007 Unified Messaging will depend on the URI types that are supported by the IP gateways, PBXs or IP PBXs in your organization. When you create a dial plan, you should know the specific URI types that are supported by your PBXs or IP PBXs. There are three formats or URI types that can be configured on Unified Messaging dial plans:

• Telephone Extension

• Session Initiation Protocol (SIP) URI

• E.164

In Unified Messaging, each time that you create a dial plan, the dial plan will, by default, be created to use the telephone extension URI format type. However, you can configure the URI type when you create a dial plan by using the New Dial Plan wizard or the New-UMDialPlan cmdlet. After you create a dial plan, you will be unable to change the URI type.

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Telephone Extension

The Telephone Extension URI type is the most common type of UM dial plan and is used with standard PBXs and IP gateways. When you configure a telephone extension or TelExtn dial plan, the IP gateways and IP PBXs must support the TelExtn or Telephone Extension URI type. When the IP gateway or IP PBX communicates with a Unified Messaging server that is associated with a dial plan, the dial plan must then be configured to support the Telephone Extension URI type. Generally, most PBXs today support the Telephone URI type. But the IP gateway and the UM dial plan must also support the Telephone URI type.

When a call is received by the PBX and the UM-enabled user is not available to answer the call, the PBX will forward the call to the IP gateway. In the header for the Session Initiation Protocol (SIP) packet that is received by the Unified Messaging server from the IP gateway, the calling and called party information will be listed in one of the following formats:

• Tel:512345

• 512345@<IP address>

The Telephone Extension format that is used is based on the configuration of the IP gateway.

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SIP URI

SIP is a standard protocol for initiating interactive user sessions that involve multimedia elements such as video, voice, chat, and gaming. SIP is a request-to-response based protocol that answers requests from clients and responses from servers. Clients are identified by SIP URLs. Requests can be sent through any transport protocol, such as UDP or TCP. SIP determines the end system to be used for the session by selecting the communication media and media parameters.

When you create a new dial plan, you have the option of creating a SIP URI dial plan that can be used in an environment that has Office Communications Server 2007 deployed or in organizations that have IP PBXs. However, in organizations that have IP PBXs, the IP PBXs must also support SIP URIs and SIP routing.

A SIP URI is the SIP addressing scheme that is used to call another person by using SIP. In other words, a SIP URI is a user’s SIP phone number. The SIP URI resembles an e-mail address and is written in the following format: sip:<user name>@<domain or IP address>:Port. When a SIP-enabled IP PBX or an IP gateway is used to send the call to a Unified Messaging server, the device will send only the SIP URI for the calling and called party in the SIP header and will not include extension numbers.

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E.164

E.164 is a standard numbering format that defines the international public telecommunication numbering plan that is used in the Public Switched Telephone Network (PSTN) and some data networks. E.164 defines the format of telephone numbers. E.164 numbers can have a maximum of 15 digits and are usually written with a plus sign (+) before the digits of the telephone number. To dial an E.164- formatted telephone number from a telephone, the appropriate international call prefix must be included in the number that is dialed. In an E.164 numbering plan for public telephone systems, each assigned number contains a country code (CC), a national destination code (NDC), and a subscriber number (SN).

When you create a new dial plan, you have the option to create an E.164 dial plan. However, if you create and configure an E.164 dial plan, the PBXs and IP PBXs must support E.164 routing. The SIP header that is received by the Unified Messaging server from an IP gateway that is associated with an E.164 dial plan will include the E.164-formatted telephone number for the calling and called party information and will be listed in the following format: Tel:+14255551234.

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VoIP Security

There are several security methods that can help you protect your Unified Messaging servers and the network traffic that is sent between your IP gateways and Unified Messaging servers and between your Unified Messaging servers and other Exchange 2007 servers in your organization. You can use Mutual Transport Layer Security (MTLS) to encrypt VoIP traffic that is passed between IP gateways, IP PBXs, and other Exchange 2007 servers and the Unified Messaging servers on your network. Using MTLS to encrypt the VoIP data is the best choice for protecting this data.

Unified Messaging can communicate with IP gateways, IP PBXs, and other Exchange 2007 computers in either a secured or an unsecured mode depending on how the UM dial plan has been configured. By default, UM dial plans communicate in an unsecured mode. You can use the Get-UMDialPlan cmdlet in the Exchange Management Shell to determine the security setting for a given UM dial plan.

Unified Messaging uses the VoIP protocols Realtime Transport Protocol (RTP) and SIP to communicate with other devices and servers. When you configure the UM dial plan to use VoIP security or secured mode, the SIP signaling channel will be encrypted. The SIP signaling channel can use SIP that is encrypted by using MTLS. However, the media channels that use RTP will still use Transmission Control Protocol (TCP), which is unsecured.

Note

An encrypted signaling media channel that uses Secure Realtime Transport Protocol (SRTP) will also use MTLS to encrypt the VoIP data. SRTP is unavailable in this release of the product. However, SRTP support is planned for a future release. This means that the SIP data and the media channels that are used by Exchange 2007 Unified Messaging will both be encrypted.

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Outlook Voice Access

There are two types of callers who will access the Unified Messaging system by using the subscriber access number that is configured on a UM dial plan: unauthenticated callers and authenticated callers. When a caller dials the subscriber access number that is configured on a dial plan, the caller is considered anonymous or unauthenticated until they input information including their voice mail extension and a PIN. However, the only option that is available to anonymous or unauthenticated callers is the directory search feature. After the caller inputs their voice mail extension and their PIN, they will be authenticated and given access to their mailbox. After they gain access to the system, they are using Outlook Voice Access. Outlook Voice Access is a series of voice prompts that give the caller access to e-mail, voice mail, calendar, and other information. Subscriber access lets authenticated callers navigate their personal information in their mailbox, place calls, or locate users by using dual tone multi-frequency (DTMF) or voice inputs.

Important

In some companies (especially in East Asia), office telephones may not have letters on the keys of the telephone. This makes the spell-the-name feature using the DTMF interface almost impossible without a working knowledge of this mapping. By default, Exchange 2007 Unified Messaging uses the E.161 key mapping. For example, 2=ABC, 3=DEF, 4=GHI, 5=JKL, 6=MNO, 7=PQRS, 8=TUV, 9=WXYZ. When inputting the combination of letters and numbers, for example "Jim1092", the numeric digits are mapped to themselves. For an e-mail alias of "Jim1092" to be entered correctly, the user must press the numbers 5461092. Also for characters other than A-Z and 0-9 there will not be a telephone key equivalent and should not be entered. For example, the e-mail alias "jim.wilson" would be entered as 546945766. Therefore, there are 11 characters to be input, but only 10 digits will be entered by the user because the '.' does not have a digit equivalent.

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Understanding Unified Messaging Mailbox Policies

This topic discusses Microsoft Exchange Server 2007 Unified Messaging (UM) mailbox policies and how they can be used in your Exchange 2007 Unified Messaging environment.

Unified Messaging Mailbox Policies

Unified Messaging Active Directory mailbox policies are required when you enable users for Exchange 2007 Unified Messaging. They are useful for applying and standardizing Unified Messaging configuration settings for UM-enabled users. You create UM mailbox policies to apply a common set of policies or security settings to a collection of UM-enabled mailboxes. You use Unified Messaging mailbox policies to set Unified Messaging settings for UM-enabled users, such as the following:

• PIN policies

• Dialing restrictions

• Other general UM mailbox policy properties

For example, you can create a UM mailbox policy to increase the level of PIN security by reducing the maximum number of logon failures for a specific group of UM-enabled users, such as executives.

Unified Messaging mailbox policies are created in the Configuration container in the Active Directory directory service by using the Exchange Management Shell or the Exchange Management Console. By default, a single UM mailbox policy is created every time that you create a UM dial plan. The new UM mailbox policy is associated with the UM dial plan and part of the dial plan name is included in the display name of the UM mailbox policy. However, you can create additional UM mailbox policies based on the needs of your organization. Although a single UM mailbox policy is required to enable users for Unified Messaging, you can create additional UM mailbox policies and apply a common set of mailbox policy settings for other groups of users.

Each UM-enabled user's mailbox must be linked to a single UM mailbox policy. After you create a UM mailbox policy, you link one or more UM-enabled mailboxes to the UM mailbox policy. This lets you control PIN security settings such as the minimum number of digits in a PIN or the maximum number of logon attempts for the UM-enabled users who are associated with the UM mailbox policy. If you prefer, you can also control message text settings or dialing restrictions for the same or a different group of UM-enabled mailboxes.

Multiple UM-enabled users can be linked to a single UM mailbox policy. However, a single user can be associated with only one UM mailbox policy. When a user is enabled for Unified Messaging, you must specify an existing UM mailbox policy to be linked to the UM-enabled user's mailbox. After you create a new UM mailbox policy and link it to a UM dial plan, the UM mailbox policy settings that are defined are then applied to the UM-enabled users. The settings that are defined on a UM mailbox policy apply only to UM-enabled users to which the UM dial plan is linked and the UM mailbox policy is associated.

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Unified Messaging Policy Examples

The following figure illustrates how Unified Messaging mailbox policies can be created to control dialing restrictions and PIN security settings for three different groups.

Example of Unified Messaging mailbox policies

Understanding Unified Messaging IP Gateways

The Unified Messaging (UM) IP gateway is a container object that logically represents a physical IP gateway hardware device. Before the IP gateway can be used to process Unified Messaging calls, the IP gateway must be represented by an object in the Active Directory directory service.

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Overview of IP gateways

Traditionally, "gateway" is a term that describes a physical device that connects two incompatible networks. With Microsoft Exchange Server 2007 Unified Messaging and other unified messaging solutions, the IP gateway is used to translate between the Public Switched Telephone Network (PSTN)/Time Division Multiplex (TDM) or circuit-switched based telephony network and an Internet Protocol (IP) or packet-switched data network.

Note

A packet-switched network is a network in which packets (messages or fragments of messages) are individually routed between nodes that may be shared by many other nodes. This contrasts with a circuit-switched network that sets up a dedicated connection between the two nodes for their exclusive use for the duration of the communication.

Exchange 2007 Unified Messaging relies on the ability of the IP gateway to translate TDM or telephony circuit-switched based protocols, such as Integrated Services Digital Network (ISDN) or QSIG, from a Private Branch eXchange (PBX) to protocols based on VoIP or IP, such as Session Initiation Protocol (SIP), Realtime Transport Protocol (RTP), or T.38 for real-time facsimile transport.

Types of IP gateways

Although there are many types and manufacturers of PBXs, IP gateways, and IP PBXs, there are basically two types of IP gateway component configurations:

• IP PBX   A single device

• PBX (legacy) and an IP gateway   Two separate components

To support Exchange 2007 Unified Messaging, one or both types of IP/VoIP device configurations are used when connecting a telephony network infrastructure to a data network infrastructure.

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IP Gateway Objects

The UM IP gateway is an Active Directory container object that contains one or more Active Directory UM hunt groups and other UM IP gateway configuration settings. UM IP gateways are created within Active Directory to logically represent a physical hardware device called an IP gateway. The UM IP gateway can represent either an IP gateway or an IP PBX. The combination of the UM IP gateway object and a UM hunt group object establishes a logical link between an IP gateway hardware device and a UM dial plan.

After the UM IP gateway is created, the IP gateway can be linked to or associated with a single or multiple UM hunt groups and UM dial plans. The UM hunt group provides a link between the UM IP gateway and a UM dial plan. By creating multiple UM hunt groups, you can associate a single UM IP gateway with multiple UM dial plans.

After you have created a UM IP gateway object, the Unified Messaging server associated with the UM IP gateway will send a SIP OPTIONS request to the IP gateway to ensure that the IP gateway is responsive. If the IP gateway does not respond to the SIP OPTIONS request from the Unified Messaging server, the Unified Messaging server will log an event with ID 1088 stating that the request failed. To resolve this issue, ensure that the IP/VoIP is available and online and that the Unified Messaging configuration is correct.

Note

Before an IP gateway can be used to process calls, a UM IP gateway must be associated with at least one UM dial plan. Also, at least one UM server must be associated with at least one UM dial plan.

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Enabling and Disabling UM IP Gateways

By default, IP gateways are left in an enabled state after they are created. However, the UM IP gateway can be enabled or disabled. If you disable a UM IP gateway, it can be in one of two disabled modes. The first disabled mode forces all associated UM servers to drop existing calls. The second disabled mode forces the UM server associated with the UM IP gateway to stop handling any new calls presented by the IP gateway.

Note

If a Unified Messaging IP gateway is deleted, the UM servers associated with the IP gateway will no longer be able accept or process new call requests from the IP gateway.

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Understanding Unified Messaging Hunt Groups

This topic discusses Microsoft Exchange Server 2007 Unified Messaging (UM) hunt groups and how UM hunt groups must be implemented in your Exchange 2007 organization to support Unified Messaging.

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What is a Hunt Group?

Hunt group is a term that is used to describe a group of Private Branch eXchange (PBX) or IP PBX resources or extension numbers that are shared by users. Hunt groups are used to efficiently distribute calls into or out of a given business unit. For example, a PBX or IP PBX might be configured to have 10 extension numbers for the sales department. The 10 sales extension numbers would be configured as one hunt group. In a PBX or IP PBX, hunt groups are used to efficiently locate an open line, extension, or channel when an incoming call is received.

In a telephony network a hunt group is defined as a set of extension numbers that are grouped as a single logical unit. When an incoming call is received, the PBX or IP PBX uses the hunt group or group of extensions that are defined to "hunt" for an available or open line, extension, or channel that can be used to receive the call.

There are multiple algorithms or methods that have been created to be used by a PBX or IP PBX to define how the open line, extension, or channel will be located. These include:

• Round robin

• Most idle

• Start with lowest number

Creating and defining a hunt group in a PBX or IP PBX minimizes the chance that a caller who places an incoming call will receive a busy signal when the call is received.

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Pilot Number

In a telephony network, a PBX or IP PBX can be configured to have a single hunt group or multiple hunt groups. Each hunt group that is created on a PBX or IP PBX must have an associated pilot number. The PBX or IP PBX uses the pilot number to locate the hunt group and in turn to locate the telephone extension number on which the incoming call was received. Without a defined pilot number, the PBX or IP PBX cannot locate where the incoming call was received.

A pilot number is the address or location of the hunt group inside the PBX or IP PBX. A pilot number is generally defined as a "blank" extension number or one extension number from a hunt group of extension numbers that does not have a person or telephone associated with it. For example, you configure a hunt group on a PBX or IP PBX to contain extension numbers 4100, 4101, 4102, 4103, 4104, and 4105. The pilot number for the hunt group is configured as extension 4100. When a call is received on the extension number 4100, the PBX or IP PBX looks for the next available extension number to determine where to deliver the call. In this case, the PBX or IP PBX looks at the extension numbers 4101, 4102, 4103, 4104, and 4105.

Using a pilot number helps eliminate busy signals and helps route incoming calls to the circuits that are available. The PBX or IP PBX pilot number, when it is used with Exchange Server 2007 Unified Messaging, is used as the target. When an incoming call is unanswered or the line is busy, the call is correctly routed to an Exchange 2007 Unified Messaging server.

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UM Hunt Groups

Unified Messaging hunt groups are critical to the operation of the Unified Messaging system. The UM hunt group is a logical representation of an existing PBX or IP PBX hunt group. UM hunt groups act as a connection or link between the UM IP gateway and the UM dial plan. Therefore, a single UM hunt group must be associated with at least one UM IP gateway and one UM dial plan.

Unified Messaging hunt groups are used to locate the PBX or IP PBX hunt group from which the incoming call was received. A pilot number that is defined for a hunt group in the PBX or IP PBX must also be defined within the UM Hunt group. The pilot number is used to match the information presented for incoming calls through the Session Initiation Protocol (SIP) signaling message information on the message. The pilot number enables the Unified Messaging server to interpret the call together with the correct dial plan so that the call can be routed correctly. The absence of a hunt group prevents the Unified Messaging server from knowing the origin or location of the incoming call. It is very important to configure the Unified Messaging hunt groups correctly, because incoming calls that do not correctly match the pilot number defined on the UM hunt group will not be answered and incoming call routing will fail.

When you create a Unified Messaging hunt group, you are enabling all Unified Messaging servers that are specified within the UM dial plan to communicate with an IP gateway. If you delete the Unified Messaging hunt group, the associated IP gateway will no longer service calls with the specified pilot number. If the IP gateway is left without remaining UM hunt groups, the IP gateway will be unable to handle incoming calls.

For more information about IP gateways, see Understanding Unified Messaging IP Gateways earlier in this white paper.

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Understanding Unified Messaging Auto Attendants

Microsoft Exchange Server 2007 Unified Messaging enables you to create a single or multiple UM auto attendants, depending on the needs of your organization. Unlike other Unified Messaging objects, such as UM dial plans and UM IP gateways, you are not required to create UM auto attendants. However, auto attendants help internal and external callers locate users or departments that exist in an organization and transfer calls to them. This topic discusses the UM auto attendant feature found in Exchange Server 2007 Unified Messaging.

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Auto Attendants

In telephony or Unified Messaging environments, an automated attendant or auto attendant menu system transfers callers to the extension of a user or department without the intervention of a receptionist or an operator. In many auto attendant systems, a receptionist or operator can be reached by pressing or saying zero. The automated attendant is a feature on most modern Private Branch eXchange (PBX) and Unified Messaging solutions.

In some auto attendant systems, there are message-only information menus and voice menus that are used so that an organization can provide business hours, directions to their premises, information about job opportunities, and answers to other frequently-asked questions. After the message plays, the caller is forwarded to the receptionist or operator or they can return to the main menu.

In more complex auto attendant systems, the menu system can be used to search for other auto attendant menus, locate a user in the system, or transfer to another outside telephone line. They can also be used to let the caller interact with the system in certain situation, such as when a student enrolls for a college class or checks their grades or when you activate a credit card over the telephone.

Although auto attendants can be very useful, if they are not designed and configured correctly, they can confuse and frustrate callers. For example, specifically in large organizations, when auto attendants are not designed correctly, callers can be led through an endless series of questions and menu prompts before they are finally transferred to a person to have their question answered.

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Unified Messaging Auto Attendants

Exchange 2007 Unified Messaging enables you to create one or more UM auto attendants depending on the needs of your organization. UM auto attendants can be used to create a voice menu system for an organization that lets external and internal callers move through the UM auto attendant menu system to locate and place or transfer calls to company users or departments in an organization.

When anonymous or unauthenticated users call an external business telephone number, or when internal callers call a defined extension number, they are presented with a series of voice prompts that help them place a call to a user or locate a user in the organization and then place a call to that user. The UM auto attendant is a series of voice prompts or .wav files that callers hear instead of a human operator when they call an organization that has Microsoft Exchange Server 2007 Unified Messaging. The UM auto attendant lets callers move through the menu system, place calls, or locate users by using dual tone multi-frequency (DTMF) or voice inputs. However, for automatic speech recognition (ASR) or voice inputs to be used, you must enable ASR on the UM auto attendant.

Important

In some companies (especially in East Asia), office telephones may not have letters on the keys of the telephone. This makes the spell-the-name feature that uses the DTMF interface almost impossible without a working knowledge of the key mappings. By default, Exchange 2007 Unified Messaging uses the E.161 key mapping. For example, 2=ABC, 3=DEF, 4=GHI, 5=JKL, 6=MNO, 7=PQRS, 8=TUV, 9=WXYZ. When inputting the combination of letters and numbers, for example "Mike1092", the numeric digits are mapped to themselves. For an e-mail alias of "Mike1092" to be entered correctly, the user will have to press the numbers 64531092. Also for characters other than A-Z and 0-9 there will not be a telephone key equivalent. Therefore, these characters should not be entered. For example, the e-mail alias "mike.wilson" would be entered as 6453945766. Even though there are 11 characters to be input, only 10 digits are entered by the user because the period (.) does not have a digit equivalent.

A UM auto attendant has the following features:

• It provides corporate or informational greetings.

• It provides custom corporate menus. You can customize these menus to have more than one level.

• It provides a directory search function that enables a caller to search the organization's directory for a name.

• It enables a caller to connect to the telephone of, or leave a message for, members of the organization.

In the Active Directory directory service, each UM auto attendant that is created is represented as an object. There is no limit to the number of UM auto attendants that you can create in Active Directory. Each Exchange 2007 Unified Messaging auto attendant can support an unlimited number of extensions. A UM auto attendant can reference one, and only one, UM dial plan. However, UM auto attendants can reference or link to other UM auto attendants.

An incoming call that is received from an external telephone number or an internal telephone extension is processed by a Unified Messaging server and then sent to a UM auto attendant that has been created. The UM auto attendant is configured by the system administrator to use pre-recorded voice (.wav) files that are then played over the telephone to the caller and that enable the caller to move through the Unified Messaging menu system. You can customize all the .wav files that are used when you configure a UM auto attendant to meet the needs of your organization.

For more information about message flow with UM auto attendants, see Unified Messaging Auto Attendant Call Processing later in this white paper.

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Auto Attendant with Multiple Languages

There are situations in which you may have to provide callers with auto attendants that have different languages. The language setting that is available on a UM auto attendant enables you to configure the default prompt language on the auto attendant. When you are using the default system prompts for the auto attendant this is the language that the caller will hear when the auto attendant answers the incoming call. This language setting will affect only the default system prompts that are provided when the Unified Messaging server role is installed. This setting will have no effect on custom prompts that have been configured on an auto attendant. The language that is selected as the default for the auto attendant is based on the version of Exchange 2007 that is installed.

When you install the U.S.-English version of Exchange 2007, there will be only one language available to configure on UM auto attendants: U.S. English. However, if you install a localized version of Exchange 2007, for example, Japanese, you will be able to configure the auto attendant that you create to use Japanese or U.S. English for the default language. Additional UM language packs can be installed on a Unified Messaging server to enable you to use other default language options on an auto attendant.

Warning

You cannot install UM language packs by using the .msi file for the language.

For example, if you have a business that is based in the United States but requires a menu system that gives callers the options of U.S. English, Spanish, and French, you must first install the UM language packs that you need. In this case, if you have installed the U.S.-English version of Exchange 2007, you would install the UM language packs for Spanish and French. However, because a Unified Messaging auto attendant can have only one language configured at a time, you would create four auto attendants: a main auto attendant that is configured to use U.S. English and then one auto attendant for each language: US English, Spanish, and French. You would then configure the main auto attendant to have the appropriate key mappings to access the other auto attendants that you have created for each language. In this example, the main auto attendant would answer the incoming call and the caller would hear, "Welcome to Contoso, Ltd. For English, press or say 1. For Spanish, press or say 2. For French, press or say 3."

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Auto Attendant Examples

The following examples demonstrate how you can use UM auto attendants together with Exchange 2007 Unified Messaging:

Example 1: At a company called Contoso, Ltd., external customers can use three external telephone numbers: 425-555-1111 (Corporate Offices), 425-555-2222 (Product Support), and 425-555-3333 (Sales). The Human Resources, Administration, and Accounting departments have internal telephone extensions and must be accessed from the Corporate Offices UM auto attendant.

To create a UM auto attendant structure that supports this scenario, create and configure three UM auto attendants that have the appropriate external telephone numbers. Create three other UM auto attendants for each department in the Corporate Offices. You then configure each UM auto attendant based on your requirements, such as the greeting type or other navigational information.

The following figure is a graphical representation of how Unified Messaging auto attendants can be used in Example 1.

How to configure multiple UM auto attendants with multiple outside business telephone lines

Example 2: At a company called Contoso, Ltd., external customers call one main number for the business, 425-555-1000. When an external caller calls the external number, the UM auto attendant answers and prompts the caller by saying, "Welcome to Contoso, Ltd. Please press or say 'One' to be transferred to corporate administration. Please press or say 'Two' to be transferred to product support. Please press or say 'Three' to be transferred to corporate information. Please press or say 'Zero' to be transferred to the operator." To create a UM auto attendant structure that supports this scenario, you create a UM auto attendant that has customized extensions that route the call to the appropriate extension number.

The following figure is a graphical representation of how Unified Messaging auto attendants can be used in Example 2.

How to configure multiple UM auto attendants with a single outside business telephone line

For more information about how to create or modify UM auto attendants, see How to Create a New Unified Messaging Auto Attendant or How to Modify a Unified Messaging Auto Attendant.

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Understanding Unified Messaging Servers

When you install the Unified Messaging server role on a computer that is running Microsoft Exchange Server 2007, a computer object is created in the Active Directory directory service. This topic discusses Unified Messaging server objects and Unified Messaging server operations that are included in Exchange 2007 Unified Messaging.

Computer Objects

Unified Messaging Active Directory computer objects are created in the Computers container during the installation of the Unified Messaging server role. The Unified Messaging objects connect the telephony infrastructure of your organization and the Exchange 2007 Unified Messaging Active Directory networking environment and are a basic part of the Unified Messaging system. The Unified Messaging computer object that is created in Active Directory is a logical representation of a physical server on which the Unified Messaging server role is installed.

Important

The Unified Messaging server must be a member of a domain before the Unified Messaging server role is installed so that a new Unified Messaging computer object can be created during the installation.

After the computer objects have been created, you can perform the procedures that are required to successfully deploy Unified Messaging on your network.

Note

You can also apply Group Policy settings to the computer after the computer that is running Exchange 2007 is added to the domain.

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Server Operation

A Unified Messaging server will not process incoming calls unless the operational state is set to enabled. By default, however, the operational status of the Unified Messaging server is set to enabled after installation. When its operational status is set to enabled, the Unified Messaging server can process incoming and outgoing voice calls and incoming fax calls and route the messages to the intended recipients in your Exchange organization.

Although the operational status of the Unified Messaging server is set to enabled after installation, the Unified Messaging server also maintains a status parameter that is used to control the operational status of the server. The status parameter lets you stop call processing so that the Unified Messaging server can be taken offline in a controlled way.

The operational status of the Unified Messaging server status can be controlled by the enable and disable commands in the Exchange Management Console and the Exchange Management Shell. The following are the three status modes for Unified Messaging servers:

• Enabled - Process all incoming calls.

• Disabled - Do not accept any new calls and drop all existing calls.

• Disabled - Do not accept any new calls but process all existing calls.

For more information about how to enable and disable a Unified Messaging server, see How to Enable Unified Messaging on Exchange 2007 and How to Disable Unified Messaging on Exchange 2007.

Even though the operational status of the Unified Messaging server is set to enabled the Unified Messaging server role is installed, the server will still be unable to correctly process and route incoming calls to UM-enabled users until it is associated with at least one UM dial plan and the UM dial plan associated with at least one UM IP gateway. For more information about how to add a Unified Messaging server to a UM dial plan, see How to Add a Unified Messaging Server to a Dial Plan.

For more information about UM IP gateways, see Understanding Unified Messaging IP Gateways earlier in this white paper.

When the Unified Messaging server is started, it will locate all IP gateways that are associated with the UM dial plans and are associated with the UM server. To detect and identify any configuration changes on either UM dial plans or UM IP gateways, the UM server will either register a change notification or re-check the configuration every 10 minutes.

If the UM IP gateway identifies any changes to the configuration, the UM server will react accordingly and either start to use or stop using the appropriate IP gateways. After a UM server is associated with a UM dial plan and is communicating with an IP gateway or IP Private Branch eXchange (PBX), you can run a set of diagnostic operations to verify the correct operation and connectivity.

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Understanding Unified Messaging Users

With Microsoft Exchange Server 2007 Unified Messaging (UM), the users in an Exchange 2007 organization can receive all their e-mail, voice, and fax messages in one mailbox. The Unified Messaging functionality found in Exchange 2007 greatly increases user productivity and enables more flexible messaging throughout an organization.

When you are creating an Exchange 2007 recipient, you are given the option of creating a mailbox or connecting to an existing mailbox. After the mailbox is created for the user or the user is connected to an existing mailbox, you must enable the mailbox so that the user can use the Unified Messaging capabilities found in Exchange 2007. After the user is enabled for UM, all e-mail, voice, and fax messages will be delivered to the user's Inbox. By using Outlook 2007, Outlook Web Access, a mobile device that is enabled for Exchange ActiveSync, or a regular or cellular telephone, the user can access their e-mail, voice and fax messages, and calendaring information.

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User Unified Messaging Properties

By default, a user who has an Exchange 2007 mailbox is not enabled for UM. You must create a mailbox for the Exchange 2007 user before the user can be enabled for UM. After the user is enabled for UM, you can manage, modify, and configure the UM properties for the user.

Note

To enable multiple UM users, use the Enable-UMMailbox Exchange Management Shell cmdlet.

There are two locations in which UM properties are stored for a user: the Mailbox object and the user's Active Directory object. When you enable a user for Unified Messaging, you set the UM property on the user's Mailbox object. After the Mailbox property is set to "enabled" for Unified Messaging, the user can use the Unified Messaging features found in Exchange 2007.

After a user is enabled for UM, the user's Unified Messaging properties are stored in the user properties and the user's mailbox. The user's Unified Messaging properties, such as the user's extension number, spoken name, and other properties for the user, are stored in the user's properties in the Active Directory directory service.

You can manage Unified Messaging (UM) properties for an Active Directory user on the mailbox of the Exchange 2007 Unified Messaging user by using the Exchange Management Shell or the Exchange Management Console.

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The Relationship of the UM User to Other Active Directory Objects

When you enable a user for Unified Messaging, the user must be associated with or linked to an existing UM mailbox policy and you must provide the extension number for the user. You can associate a user with a UM mailbox policy by using the Enable-UMMailbox cmdlet or by selecting the UM mailbox policy when you create the user's Exchange mailbox.

A UM mailbox policy contains settings such as the dialing restrictions and PIN policies for a user. When a UM mailbox policy is created, the UM mailbox policy must be associated with only one UM dial plan. The UM dial plan is then associated with at least one Unified Messaging server. Any Unified Messaging server that is associated with the UM dial plan can provide Unified Messaging services for a UM-enabled user who uses the UM dial plan. Associating these Active Directory objects in this manner delivers the Unified Messaging services by using Active Directory. After the user is enabled for UM, the settings from a UM mailbox policy object are applied to the UM-enabled user.

Note

In a circuit-switched telephony environment, the user's telephone must be programmed in the Private Branch eXchange (PBX) to forward busy or unanswered calls to a UM IP gateway that is associated with the user's dial plan.

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Overview of the Unified Messaging Call Processing

This section introduces topics that describe how Microsoft Exchange Server 2007 Unified Messaging handles message flow in different incoming call scenarios.

Incoming Calls Overview

Exchange 2007 Unified Messaging handles the following types of incoming calls:

• Voice

• Fax

• Outlook Voice Access

• Play on Phone

• Auto attendant

Note

Call handling is a term that describes how incoming calls are answered and handled by a computer that is running Exchange 2007 that has the Unified Messaging server role installed.

When an incoming call is received by an Exchange 2007 Unified Messaging server, the call is answered and then routed by using a message transport such as Simple Mail Transfer Protocol (SMTP), MAPI, remote procedure call (RPC), or Lightweight Directory Access Protocol (LDAP). The message transport that is used when messages are routed depends on the type of incoming call that the Unified Messaging server answers.

Exchange 2007 Unified Messaging depends on the Active Directory directory service to route incoming calls. Each UM-enabled recipient must have a telephone extension number listed in Active Directory for call answering to function correctly. The extension number for the recipient is listed in Active Directory and is mapped to the extension number that is configured on the user's UM-enabled Exchange mailbox. When a Unified Messaging server answers a call, an Active Directory lookup is performed to locate the appropriate UM-enabled recipient and the message is routed to the recipient's mailbox.

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Message Flow

Message flow in Unified Messaging is the process by which a message that is received by a Unified Messaging server is routed in an Exchange 2007 organization. Depending on the type of incoming message or call that is answered by a Unified Messaging server, a different transport protocol is used.

Note

In earlier versions of Exchange, routing groups were used to route messages between bridgehead servers—known in Exchange 2007 as Hub Transport servers. There are no routing groups in Exchange 2007.

For example, in an incoming call scenario that includes incoming voice and fax messages, a Hub Transport server uses the SMTP transport to submit the voice or fax mail message to the Mailbox server. In a routing scenario that includes multiple Hub Transport servers, the incoming voice or fax mail message is first submitted to the closest Hub Transport server and is then routed to the appropriate Mailbox server that contains the UM-enabled mailbox.

Note

To make sure that all incoming messages are transmitted and delivered to UM-enabled recipients, the Unified Messaging servers use a spooling or re-try algorithm. The Unified Messaging servers try to connect to a Hub Transport server every 30 seconds to submit all messages that are stored on the Unified Messaging server.

For more information about how the Exchange 2007 Unified Messaging server handles incoming calls and how the messages flow in Exchange 2007 Unified Messaging, see the following topics:

• Unified Messaging Voice and Fax Message Flow

• Unified Messaging Outlook Voice Access Message Flow

• Unified Messaging Auto Attendant Message Flow

• Unified Messaging Play On Phone Message Flow

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Unified Messaging Voice and Fax Call Processing

Incoming voice and fax messages are received by your organization's telephony network and then passed to a Microsoft Exchange Server 2007 Unified Messaging server that handles and routes the incoming call. This topic discusses the message flow for incoming voice and fax messages that are received by a Unified Messaging server.

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Voice and Fax Incoming Messages

Voice and fax calls that come in to an Exchange 2007 organization can be received from users who are inside or outside the organization. When a caller places a call to a UM-enabled user's telephone extension and the user is unavailable to answer the call, the Private Branch eXchange (PBX) forwards or routes the incoming call to an IP gateway and then to the Unified Messaging server. In a Unified Messaging system that uses an IP PBX, the IP PBX forwards the incoming message to the Unified Messaging server. The IP gateway or the IP PBX translates or converts the incoming stream into a VoIP protocol such as the Session Initiation Protocol (SIP) for incoming voice messages or the T.38 protocol for incoming fax messages. The stream of IP data is then passed on to the Unified Messaging server. After the Unified Messaging server receives the call, the Unified Messaging server processes the message and determines how to route the message.

The following figure illustrates how incoming voice and fax messages flow in an Exchange 2007 organization.

The flow of incoming voice and fax messages in an Exchange 2007 organization

Unified Messaging Outlook Voice Access Call Processing

When an authenticated UM-enabled user calls in to the Microsoft Exchange 2007 Unified Messaging system, the call is received by your organization's telephony network and then passed to an Exchange 2007 Unified Messaging server that handles and routes the incoming call. This topic discusses the message flow for incoming Outlook Voice Access calls to an Exchange 2007 Unified Messaging server.

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Outlook Voice Access

With Exchange 2007 Unified Messaging, UM-enabled users or subscribers can access their e-mail, contacts, and calendaring information by using a standard analog, digital, or cellular telephone. When a UM-enabled user uses Outlook Voice Access, they can perform the following tasks:

• Listen to new and saved e-mail and voice mail messages.

• Forward, reply, save, and delete e-mail and voice mail messages.

• Interact with their calendar.

• Locate a person in the global address list (GAL) or personal contacts.

• Send a voice message to a person

• Change their PIN, spoken name, or greetings.

• For more information about subscriber access in Exchange 2007 Unified Messaging, see Understanding Unified Messaging Subscriber Access earlier in this white paper.

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Outlook Voice Access Message Flow

Outlook Voice Access incoming calls and messages that are created by using Outlook Voice Access are routed to an Exchange 2007 Unified Messaging server and then to the Mailbox server. However, if a message is submitted by using Outlook Voice Access, for example, a change in the schedule of a meeting from a subscriber, the message is submitted to a Hub Transport server before it is routed to the appropriate mailbox for the Exchange 2007 recipient or recipients.

The following figure illustrates how incoming calls and messages placed by subscribers or UM-enabled users flow in an Exchange 2007 organization.

Outlook Voice Access message flow in an Exchange 2007 organization

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Unified Messaging Auto Attendant Call Processing

Incoming calls that are received by a Unified Messaging (UM) auto attendant are first passed through your organization's telephony network and then to a Microsoft Exchange Server 2007 Unified Messaging server that handles and routes the incoming call. This topic discusses the message flow for incoming messages that are received by an Exchange 2007 Unified Messaging auto attendant.

UM Auto Attendants

When external or anonymous callers place a call by using an external business telephone number, or an internal anonymous caller places a call to an internal extension number, they are presented with voice prompts to help them navigate the Unified Messaging menu system. The UM auto attendant is a set of voice prompts or .wav files that are played to callers in place of a human operator or receptionist when they call into an organization that has Exchange 2007 Unified Messaging. Exchange 2007 Unified Messaging enables you to create one or more auto attendants depending on the needs of your organization. For more information about UM auto attendants, see Understanding Unified Messaging Auto Attendants earlier in this white paper.

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Auto Attendant Message Flow

When a call is received by an Exchange 2007 Unified Messaging server, the Unified Messaging server performs a Lightweight Directory Access Protocol (LDAP) query to an Active Directory directory service domain controller to determine how to handle the incoming call.

The following figure illustrates the message flow process when Unified Messaging auto attendants are used in an Exchange 2007 organization.

UM auto attendant message flow

Unified Messaging Play on Phone Call Processing

Incoming calls that are placed by users who are using the Play on Phone feature are received and routed by a computer that is running Microsoft Exchange Server 2007 that has the Unified Messaging server role installed. This topic discusses the message flow for calls that are made by a UM-enabled user who uses the Play on Phone feature in Exchange 2007 Unified Messaging.

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Play on Phone

The Exchange 2007 Unified Messaging Play on Phone feature enables a UM-enabled user to access a voice mail message. However, instead of playing the media file over their computer speakers, they can listen to the message on a telephone.

When users sit in office cubicles, use a public computer, have a computer that is not enabled for multimedia, or have a voice message that is confidential, a UM-enabled user may not want to or may be unable to play a voice message over their computer speakers. The Play on Phone feature lets the UM-enabled user play the voice message over a telephone. The Play on Phone feature is available in Exchange 2007 Outlook Web Access and in Office Outlook 2007.

The following figure illustrates how Exchange 2007 Unified Messaging routes the incoming calls for UM-enabled users who use the Play on Phone feature.

Message flow for incoming calls when the Play on Phone feature is used

Note

The Unified Messaging Web services are installed on a computer that has the Client Access server role installed. Unified Messaging Web services enable Session Initiation Protocol (SIP) functionality on a Client Access server. This functionality enables a user to record a voice mail greeting or use the Play on Phone feature. The Unified Messaging server uses only SIP to communicate. Therefore, the UM Web service is installed on a computer running the Client Access server role and is required to enable the Client Access server to communicate with the Unified Messaging server.

Important

By default, SIP data, which includes Unified Messaging server settings and other call information that is sent from a Unified Messaging server to a Client Access server, is not encrypted. This could pose a security threat. To help protect all SIP traffic, use Transport Layer Security (TLS) to encrypt the traffic between a Client Access server and a Unified Messaging server by configuring TLS security settings on the UM dial plan. For more information about SIP security and TLS, see Understanding Unified Messaging VoIP Security earlier in this white paper.

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IP Gateway Support

Integrating Exchange Server 2007 Unified Messaging with your company's telephony network is one of the most significant deployment challenges when you deploy Unified Messaging. Interoperating with Exchange 2007 Unified Messaging will depend on your specific PBX or IP PBX configurations and may also require that you install IP gateways, purchase additional PBX hardware, or configure and enable features on your PBXs or IP PBXs. In some cases, the PBX may cause reduced functionality or limitations in the Unified Messaging features. This is especially true for IP PBXs. This section discusses the manufacturers and specific models of IP gateways that you can configure to support Exchange 2007 Unified Messaging.

Important

We recommend that all customers who plan to deploy Exchange 2007 Unified Messaging obtain the assistance of a Unified Messaging specialist. They will help make sure that there is a smooth transition to Exchange 2007 Unified Messaging from a legacy voice mail system. Performing a new deployment or upgrading a legacy voice mail system requires significant knowledge about PBXs and Exchange 2007 Unified Messaging. For more information about how to contact a Unified Messaging specialist, see the Microsoft Exchange Server 2007 Unified Messaging (UM) Specialists Web site.

There are many models and manufacturers of PBXs, IP gateways, and IP PBXs. However, there are basically two configurations for IP gateway devices:

• IP PBX   A single hardware device.

• PBX (legacy) and an IP gateway   Two separate hardware devices.

Dialogic and AudioCodes IP gateways have been tested and are supported for Exchange 2007 Unified Messaging.

For more information about the latest support and configuration information available for AudioCodes IP gateways, see the Microsoft Exchange Server 2007 UM Resource Page.

For more information about the latest support and configuration information for Dialogic IP gateways, see the Dialogic Documentation Web site.

Note

The third-party Web site information in this topic is provided to help you find the technical information you need. The URLs are subject to change without notice.

Correctly configuring IP gateways for your organization is a difficult deployment task that must be completed to successfully deploy Exchange 2007 Unified Messaging. To help answer questions and give you the most up-to-date IP gateway configuration information, see the Telephony Advisor for Exchange Server 2007 Web site. This Web site gives you IP gateway configuration notes and files that you must have to correctly configure your organization's IP gateways to work with Exchange 2007 Unified Messaging.

Exchange 2007 Unified Messaging relies on an IP gateway that can receive incoming calls from a legacy PBX or on an IP PBX that can receive incoming calls and then correctly forward those incoming calls to a Unified Messaging server in your organization.

Important

We recommend that all customers who plan to deploy Exchange 2007 Unified Messaging obtain the assistance of a Unified Messaging specialist. A Unified Messaging specialist helps you make sure that there is a smooth transition to Exchange 2007 Unified Messaging from a legacy voice mail system. Performing a new deployment or upgrading a legacy voice mail system requires significant knowledge about PBXs and Exchange 2007 Unified Messaging. For more information about how to contact a Unified Messaging specialist, see the Microsoft Exchange Server 2007 Unified Messaging (UM) Specialists Web site.

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IP PBX Support

An IP PBX is a telephone switching system inside an enterprise that switches calls between Voice over IP (VoIP) users on local lines and lets all users share a certain number of external telephone lines. The typical IP PBX can also switch calls between a VoIP user and a traditional telephone user, or between two traditional telephone users much like a conventional PBX does. With a conventional PBX, you must have separate networks for voice and data communications. One of the main advantages of an IP PBX is that it uses converged data and voice networks. This means that network access, VoIP communications, and traditional telephone communications are all possible by using a single line to each user. Like a traditional PBX, an IP PBX is typically owned by an organization.

There are many manufacturers of IP PBXs. However, for an IP PBX to interoperate with Exchange 2007 Unified Messaging, the IP PBX generally must support the following:

• Session Initiation Protocol (SIP) over Transmission Control Protocol (TCP)

• T.38 for fax

However, even if a specific IP PBX supports SIP over TCP and T.38, there is no guarantee that the IP PBX will successfully interoperate with Exchange 2007 Unified Messaging.

Correctly configuring your organization's IP PBXs is a difficult but required deployment task. To help answer questions and give you the most up-to-date IP PBX configuration information, see the Telephony Advisor for Exchange Server 2007 Web site. This Web site gives you IP PBX configuration notes and files that are required to correctly configure your organization's IP PBXs to work with Exchange 2007 Unified Messaging.

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Cisco CallManager

Cisco CallManager tracks all active VoIP network components. These components include telephones, gateways, conference bridges, voice mail boxes, and other components. Cisco CallManager frequently uses the Skinny Client Control Protocol (SCCP) as a communications protocol for signaling the hardware endpoints of the system, such as IP-based telephones, or it uses SIP to pass call signaling to IP gateways. Cisco CallManager evaluates numbers that are dialed and starts IP gateway events to receive or send calls to the Public Switched Telephone Network (PSTN).

Exchange 2007 Unified Messaging has been tested for use with Cisco CallManager version 5.x. If you have Cisco CallManager 5.x on your network, you will be able to connect Exchange 2007 Unified Messaging servers directly to CallManager without the requirement of an IP gateway. Many of the features that are included with Exchange 2007 Unified Messaging are fully functional with Cisco CallManager 5.x. However, the Message Waiting Indicator (MWI) feature does not work and faxing does not work because the T.38 faxing protocol is not supported by Cisco CallManager.

Warning

We do not recommend Cisco CallManager 4.x for use in Exchange 2007 Unified Messaging production environments.

There are various limitations related to Cisco CallManager 4.x. Therefore, we recommend that you use it only for test or lab environments. The limitations are as follows:

• Call transfers do not work. Therefore, the auto attendant feature cannot transfer incoming calls.

• Faxing does not work.

• Accessing a user's voice mail and e-mail messages from a telephone is unreliable.

• The Message Waiting Indicator (MWI) feature does not work.

  Note

  Exchange 2007 Unified Messaging does not include support for the Message Waiting Indicator (MWI) feature. However, you can obtain information about how to enable this feature by visiting the Geomant Web site. This third-party application extends Exchange 2007 Unified Messaging to include the Message Waiting Indicator (MWI) and Short Message Service text messaging capability.

  Note

  The third-party Web site information in this topic is provided to help you find the technical information you need. The URLs are subject to change without notice.

To configure Cisco CallManager 4.x for your test environment, perform the following tasks:

• Configure it to send SIP messages to port 5061 on the Unified Messaging server.

• Create a SIP Trunk and an associated route pattern.

Supported IP PBXs

Cisco CallManager version 5.0 has been tested for direct IP interoperability with Exchange 2007 Unified Messaging. However, a listing of the IP-PBXs that are supported is available on the Telephony Advisor for Exchange Server 2007 Web site.

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PBX Support

A PBX, sometimes known as a telephone switch or telephone switching device, is a device that connects office telephones in a business to the public telephone network. The central functions of a PBX are to route incoming calls to the appropriate extension in an office, and to share telephone lines between extensions. Users of the PBX share a certain number of outside lines for making telephone calls external to the PBX.

Most medium-size and larger organizations use a PBX because it is much less expensive than connecting an external telephone line to every telephone in the organization. In addition, it is easier to call someone who has an extension number within the same PBX because the number that you dial is typically merely three or four digits.

Correctly configuring your organization's PBXs is frequently one of the more difficult deployment tasks because PBXs are very different and their functionality depends on the PBX model and software that is installed. To help answer questions and give you the most up-to-date PBX configuration information, see the Telephony Advisor for Exchange Server 2007 Web site. This Web site gives you PBX configuration notes and files that are required to correctly configure your organization's PBXs to work with Exchange 2007 Unified Messaging.

In many organizations today, accessing e-mail and voice mail is very important to the success of daily operations. To provide continuous access to e-mail and voice mail, you must correctly plan and implement a solution for your Microsoft Exchange Server 2007 organization that will help guarantee the availability of the servers that provide these services.

To provide a highly scalable and available solution in Exchange 2007 Unified Messaging, you must understand how the Unified Messaging components can be scaled to support your users. You must also understand how to implement a solution that will make your Unified Messaging servers highly available.

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Unified Messaging Server Scalability

Scalability is defined as the capability to increase resources to increase the capacity of a given service. There are two types of scalability that can be used to increase the capacity of Unified Messaging servers in your organization: horizontal and vertical. In Exchange 2007 Unified Messaging, when you scale vertically, you add hardware resources to a single Unified Messaging server or multiple Unified Messaging servers, for example:

• Adding more hard disk space for message storage

• Increasing the speed or number of processors

• Increasing the amount or speed of RAM

• Increasing the number of network adapters or increasing the number of local area network (LAN) ports in a single network adapter

In Unified Messaging, when you scale horizontally, you install the Unified Messaging server role on new Unified Messaging servers and add more Unified Messaging servers to a dial plan to increase the number of incoming concurrent calls that the system can accept. To scale your Unified Messaging environment horizontally, you can also increase the number of IP gateways. This increases the number of ports that are available to be used for incoming calls.

Exchange 2007 Unified Messaging provides an efficient and simple deployment model that is highly scalable without increasing the complexity of the deployment. There are many deployment models for Unified Messaging in your organization. But the recommended deployment model for Unified Messaging is to centralize your Unified Messaging servers. All the available deployment options for Unified Messaging have several steps in common that are required to create a scalable system to support many Unified Messaging users. These steps are as follows:

1. Provision PBX lines   The first step in building a highly scalable UM solution is to provision PBX lines.

2. Organize channels   After you have provisioned PBX-based voice channels, you can organize the channels as hunt groups.

3. Deploy IP gateways   After you have organized your voice channels as hunt groups, you will need to deploy your IP gateways. The channels that you organized as hunt groups should end at the IP gateways that you will be deploying. IP gateways are used with a legacy PBX to convert the circuit-switched protocols found on a telephony network to IP-based packet-switched protocols.

4. Add more Unified Messaging servers to a dial plan   If you must increase the number of calls that can be handled by Unified Messaging, you can install and configure additional Unified Messaging servers and add them to a dial plan. In most cases, IP gateways will use DNS to load balance between the existing Unified Messaging servers and the additional Unified Messaging servers.

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Network Traffic

Every incoming call that is received from an IP gateway will generate IP-based network traffic and will consume some amount of your available network bandwidth. Because all the IP-based calls are routed directly to your Unified Messaging servers from the IP gateways on your network and this IP-based network traffic consumes some available bandwidth, you should follow these recommendations and guidelines:

• Perform an analysis of the network traffic to determine current usage patterns and find any potential issues. On most networks, bandwidth demand is not evenly distributed throughout business hours.

• Put your PBXs physically close to your IP gateways.

• Put your IP gateways and your Unified Messaging servers close together.

• Put your Unified Messaging servers and IP gateways on the same subnet.

• Put your Unified Messaging servers and IP gateways on the same virtual local area network (VLAN).

• Put your Unified Messaging servers close to other computers that have Exchange 2007 server roles installed, including Mailbox, Hub Transport, and Client Access servers.

• End your Wide Area Network (WAN) connections close to where your telephony equipment is located.

• In branch office scenarios or over WAN connections, use the G.723.1 codec instead of the G.711u or G.711A codec to minimize the network traffic that is passed between your IP gateways and your Unified Messaging servers.

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Unified Messaging Servers

Generally, Unified Messaging scalability is determined by the number of concurrent calls. By default, a single Unified Messaging server can accept a maximum of 100 concurrent voice calls and 100 concurrent fax calls. These calls can be either incoming or outgoing and can be generated when a user leaves a voice mail message, when an Outlook Voice Access user accesses their Exchange 2007 mailbox, or by a user who uses the Play on Phone feature to listen to their voice messages. Although the number of concurrent calls is an important factor to consider when you build a scalable Unified Messaging infrastructure, you must also determine the best codec to use to encode the voice messages and the types and number of users who you have to support.

• Number of concurrent calls   Although, by default, a Unified Messaging server can accept 100 concurrent voice messages and 100 concurrent fax messages, a single Unified Messaging server can be configured to accept a maximum of 200 concurrent voice messages and 200 concurrent incoming fax messages. When you increase the number of concurrent connections on a single Unified Messaging server, more system resources are required than if you decrease the number of concurrent connections. It is especially important to decrease this setting on low-end, slower computers on which the Unified Messaging server is installed. Performance counters are available and the Get-UMActiveCalls cmdlet can also be used to monitor the current number of concurrent calls that are connected to a Unified Messaging server.

  If the number of concurrent calls required by your organization is larger than the number that is supported by a single Unified Messaging server, you can scale horizontally and increase the capacity of concurrent calls by installing the Unified Messaging server role and then adding the Unified Messaging server to a dial plan.

• Voice mail storage codec   The term codec is a combination of the words coding and decoding and relates to digital data. A codec is a computer program or software that transforms digital data into an audio file format or streaming audio format.

  In Exchange Unified Messaging, there are two general types of codecs: the codec that is used between IP gateways and the codec that is used to encode voice messages. The Windows Media Audio (WMA), Group System Mobile (GSM) 06.10, and G.711 Pulse Code Modulation (PCM) Linear audio codecs are used to create .wma and .wav audio files for voice messages. However, the file type that is used depends on the audio codec that is used to create the voice message audio file. In Exchange Unified Messaging, the .wma audio codec creates .wma audio files and the GSM 06.10 and G.711 PCM Linear audio codecs produce .wav audio files. Therefore, depending on the codec that is used, an audio file in .wma or .wav format is sent together with the e-mail message to the intended voice mail recipient. The size of Unified Messaging voice messages depends on the size of the attachment that holds the voice data. Additionally, the size of the attachment depends on the following factors:

  • The duration of the voice mail recording

  • The audio codec that is used

  • The audio file storage format

  The following figure illustrates how the size of the audio file depends on the duration of the voice mail recording for the three audio codecs that you can use in Unified Messaging.

  Note

  In this figure, the average length of a call-answered voice message is approximately 30 seconds.

  Audio file size

  

  The sample bit rate (bit/sec) and compression properties for each audio codec that is used in Unified Messaging are as follows:

  • WMA – 16-bit – compressed file

  • G.711 – 16-bit – uncompressed file

  • GSM 06.10 – 8-bit – compressed file

  If you use the WMA codec, we estimate that each Unified Messaging server can handle 60 to 75 concurrent IP-based calls. This estimate is based on the assumption that 14 percent of all the IP-based calls arrive during the single busiest hour of a day. Based on these two assumptions, and assuming that your users access their voice messages frequently by using Outlook Voice Access, we estimate that each Unified Messaging server can support between 2,000 and 10,000 users.

  Generally, you should allow for the following number of concurrent calls per Unified Messaging server:

  • 60 if the default dial plan codec is WMA

  • 75 if the default dial plan codec is GSM

• Types of users   There are two types of users who access the Unified Messaging system: authenticated users and unauthenticated users. These two types of users consume Unified Messaging resources. When you build a scalable Unified Messaging environment, you must consider the effect that these users will have and the resources that each of these users will consume.

  • Authenticated   Authenticated users are UM-enabled and can access their mailbox by using Outlook Voice Access. Authenticated users consume Unified Messaging server resources in several ways, including by directly calling in to a subscriber access number, logging on to their mailboxes, accessing their messages, calendar, contacts or the directory, and by using a Unified Messaging server to play voice messages over a telephone using the Play on Phone feature. They can also indirectly consume resources by transferring a call, sending a voice message, or calling a user's extension number and leaving a voice message or sending a fax.

  • Unauthenticated   Users who call in to a Unified Messaging auto attendant or call in to a subscriber access number but do not log on to their mailbox are unauthenticated callers. However, Unified Messaging resources are used to service their requests. Every time that a caller calls in to a UM auto attendant or uses a subscriber access number but does not log on to their mailbox, they still consume resources by transferring a call, sending a voice message, transferring to another auto attendant, transferring to another telephone number, or listening to recorded audio prompts.

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IP Gateways and Unified Messaging Scalability

Unified Messaging relies on the ability of the IP gateway to translate TDM or telephony circuit-switched based protocols, such as Integrated Services Digital Network (ISDN) or QSIG, from a PBX to protocols based on VoIP or IP, such as SIP, RTP, or T.38 for real-time facsimile transport.

IP gateways are available from multiple manufacturers in sizes and models that range from 4 ports to 32 ports. You can deploy as many IP gateways as necessary to provide for capacity and fault tolerance. If the number of calls or ports that are required is larger than the number of calls or ports that are supported by a single IP gateway, you can scale horizontally and increase the number of calls that can be accepted or the number of ports by installing and configuring additional IP gateways, creating the UM IP Gateway object, and configuring the appropriate hunt groups to support your environment.

It is equally important to match the number of IP gateways that you have in your environment with the number of Unified Messaging servers that are available. For example, you should not configure 10 IP gateways that are each connected by using a T-1 line to a single Unified Messaging server. This would mean that the Unified Messaging server would have to support 240 concurrent incoming calls. You should consider this and scale your IP gateways to Unified Messaging servers appropriately.

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Unified Messaging Availability

Minimum uptime requirements may vary among organizations. However, every organization wants to achieve a high level of uptime, especially for their telephony system. An organization's telephony system is frequently business-critical and must be highly available to users. One of the factors that you must consider when you deploy a Unified Messaging system is the ability for the system to provide services for users when a key component such as a Unified Messaging server or an IP gateway becomes unavailable.

• Unified Messaging servers   In Exchange 2007, Unified Messaging is designed to run as a service and a worker process. This means that if the service is using lots of system resources or has become unresponsive, the worker process can be recycled. The UM worker process is responsible for dealing with outages in Mailbox servers, Hub Transport servers, and domain controllers. If, for example, a Mailbox server for a user is unavailable, the Unified Messaging server will continue to accept calls on behalf of the user. However, the user's custom greeting will not be played. Instead, a standard greeting will be used for calls to that user. Additionally, if the Hub Transport server is unavailable, the Unified Messaging server will continue to accept calls and queue the calls, depending on how you have configured the queuing limit, until the Hub Transport server is available. However, in a situation where all domain controllers are unavailable, the Unified Messaging server will be unable to accept calls.

  Unified Messaging deployments can be made more flexible and more available by adding Unified Messaging servers to a single dial plan in an N+1 configuration. This means that if you need two Unified Messaging servers, you would install and configure an additional Unified Messaging server so that you would have a Unified Messaging server to replace a Unified Messaging server that is failing or must be taken offline.

  When you add multiple servers to a single dial plan, the IP gateway will try to connect to a Unified Messaging server that is listed in the configuration on the IP gateway by IP address, or by fully qualified domain name (FQDN) for TLS deployments. If the Unified Messaging server is unavailable, the IP gateway will try to connect to the Unified Messaging server again after 5 seconds. If there is no response from the Unified Messaging server, the IP gateway will try to connect to the next Unified Messaging server in the list that is configured on the IP gateway.

• IP gateways   If you want to create redundancy to provide for IP gateway availability, you should add multiple IP gateways in an N+1 configuration. This means that, if you need two IP gateways, you would install and configure an additional IP gateway so that you would have an IP gateway to replace an IP gateway that is failing or must be taken offline.

  You must configure your PBX so that it will send the incoming calls that it has received to different IP gateways. After you configure the PBX, the PBX will detect a failure or no signal or that a port is not answering calls. This will enable the PBX to redirect calls to an IP gateway that can answer incoming calls.

  The IP gateways that are supported by Unified Messaging can be configured to route calls to Unified Messaging servers in a round-robin manner. To enable an IP gateway, you must configure each IP gateway with the IP addresses for your Unified Messaging servers that will be answering calls from the IP gateway. These are the Unified Messaging servers that are associated with the same dial plan as the UM IP Gateway object that logically represents the IP gateway. This will enable all the UM IP gateways to forward incoming calls to the Unified Messaging servers that are associated with the same dial plan. Then, if an IP gateway fails, the PBX will send the call to an IP gateway that can answer the call. The IP gateway, in turn, will forward the call to a Unified Messaging server within the same dial plan. If the call is sent to a Unified Messaging server that is not available, the IP gateway will try to contact the Unified Messaging server again. If it is unsuccessful in contacting the Unified Messaging server, it will then use the next Unified Messaging server in the list that is configured on the IP gateway to answer the call. However, not all supported IP gateways can be configured to support both load balancing and to be able to detect if a server has been taken offline or is failing.

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Load Balancing in Unified Messaging

Exchange 2007 Unified Messaging deployments can be made more flexible by deploying multiple Unified Messaging servers to a single dial plan to balance the load of incoming calls. The IP gateways that are supported by Unified Messaging can be configured to route calls in a round-robin manner to balance the load between multiple Unified Messaging servers that are within a dial plan.

Round robin is a method for distributing the workload among multiple servers. However, round robin does not by itself enable an IP gateway to detect a server failure. If one of the Unified Messaging servers fails and if the IP gateway cannot detect that a Unified Messaging server is unavailable, the IP gateway will continue to send incoming calls to the Unified Messaging server until you detect the failure and remove the server from the dial plan. After you remove the Unified Messaging server from the dial plan, you should also remove the IP address or FQDN for the Unified Messaging server from the configuration on the IP gateway.

Unified Messaging does not use round-robin DNS or Network Load Balancing (NLB) to distribute incoming calls. Round-robin DNS can be used on multi-homed computers and can be used to distribute the load for other services, but not for Unified Messaging. NLB is used with other services to distribute client requests and to automatically detect whether a server is unavailable, and then to redistribute other client requests to the remaining server. However, it also cannot be used with Unified Messaging. The only way to distribute or balance the load between Unified Messaging servers in a dial plan is to configure the IP gateway to use the IP addresses or FQDNs of the Unified Messaging servers in the dial plan. The IP gateway will use the list to distribute the load across all the Unified Messaging servers in the dial plan and can also detect a server failure if the IP gateway supports this functionality.

Another way to load balance your Unified Messaging deployment is to configure PBX hunt groups to connect to multiple IP gateways and then configure the hunt groups to load balance across the IP gateways.

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Conclusion

This white paper outlines the general information that you must have to plan your Unified Messaging deployment for Exchange Server 2007. After you have read White Paper: Unified Messaging Technical Overview and this white paper, you should be prepared to plan your Unified Messaging deployment.

Additional Information

For more information about the technical concepts for Unified Messaging, see White Paper: Unified Messaging Technical Overview.

For more information about how to deploy Unified Messaging, see White Paper: Deploying Exchange 2007 Unified Messaging - Part 2.

For more information about how to manage Unified Messaging, see White Paper: Managing Exchange 2007 Unified Messaging - Part 3.

For more information about educating users for Unified Messaging, see White Paper: Educating Information Workers About Unified Messaging - Part 4.

For more information about how to test and troubleshoot your Unified Messaging deployment, see White Paper: Testing and Troubleshooting Unified Messaging - Part 5.

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