Differences Between an On-Premises Deployment of UM and UM Deployment in the Cloud

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Applies to: Office 365 for enterprises

If you are planning to migrate your UM mailboxes to the cloud or to set up your organization to support UM coexistence, you need to understand the following differences between an on-premises deployment of UM and UM deployment in the cloud:

  • Management interfaces   If your UM deployment is cloud-based only, you use the Web-based Exchange Control Panel to manage UM. In a coexistence scenario, where you have both on-premises and cloud-based UM users, you use the Exchange Management Console.
  • UM server requirements   If your UM deployment is cloud-based only, you don't need to set up and maintain UM servers on-premises. You use the UM service in the cloud instead. This means you don't have to associate your UM dial plans with a UM server, and many server-side configuration options, such as language pack management and server logs, aren't necessary. If you are setting up your organization for UM coexistence, you have to set up and maintain UM servers for your on-premises UM deployment.
  • VoIP security options   In a cloud-based UM deployment, communication between your Private Branch eXchange (PBX) and the UM servers occurs over the Internet, so the VoIP security setting is automatically set to Secured. This enforces Transport Layer Security (TLS) and Secure Real-time Transport Protocol (SRTP) when VoIP traffic is routed between your on-premises session border controller (SBC) and the UM service in the cloud. In an on-premises UM deployment, you can choose the security setting.
  • UM IP gateway configuration   When you configure your UM IP gateway in the cloud, point the gateway to your on-premises SBC, instead of directly to the IP PBX. For more information, see Create a New UM IP Gateway. In an on-premises UM deployment, you point your UM IP gateway directly to your IP PBX.
  • Forwarding address   For an on-premises deployment of UM, you point your UM IP gateway directly to your UM server. In a cloud-based UM deployment, the UM server addresses aren't static, so you have to configure your SBC to point to a forwarding address for the UM service in the cloud. For more information, see Forward Calls from Your Physical Telephone Device to UM.
  • Speech functionality   Speech functionality is limited in some areas of UM in the cloud. Outlook Voice Access in the cloud uses speech for most functionality, but switches to Telephony User Interface (TUI) when users search in the shared address book. Also, speech-enabled auto attendants aren't supported in cloud-based UM deployments.
  • Licensing   For Microsoft Office 365 for enterprises, you must have a license that includes UM for the mailboxes that you UM-enable. You manage licensing in the Microsoft Office 365 portal. For more information, see Assign a License to New Mailboxes in Office 365.