1.1 Glossary

This document uses the following terms:

acknowledgment (ACK): A signal passed between communicating processes or computers to signify successful receipt of a transmission as part of a communications protocol.

big-endian: Multiple-byte values that are byte-ordered with the most significant byte stored in the memory location with the lowest address.

client: A computer on which the remote procedure call (RPC) client is executing.

coalesced payload: A special form of payload that consists of multiple traditional payloads combined into a single packet.

command frame (CFRAME): A special DirectPlay 8 control frame that does not carry application payload data. For more information, see the DirectPlay 8 Protocol: Reliable Specification ([MC-DPL8R] section 2.2.1). See Also, data frame.

CRC-16-IBM algorithm: The CRC-16-IBM algorithm polynomial is x^16 + x^15 + x^2 + 1. Normal and reversed representations are "0x8005" or "0xA001".

cyclic redundancy check (CRC): An algorithm used to produce a checksum (a small, fixed number of bits) against a block of data, such as a packet of network traffic or a block of a computer file. The CRC is a broad class of functions used to detect errors after transmission or storage. A CRC is designed to catch random errors, as opposed to intentional errors. If errors might be introduced by a motivated and intelligent adversary, a cryptographic hash function should be used instead.

data frame (DFRAME): A DirectPlay 8 frame that exists in the standard connection sequence space and typically carries application payload data. The total size of the DFRAME header and payload should be less than the Maximum Transmission Unit (MTU) of the underlying protocols and network. For more information, see the DirectPlay 8 Protocol: Reliable Specification ([MC-DPL8R] section 2.2.2). See Also, command frame.

DirectPlay: A network communication library included with the Microsoft DirectX application programming interfaces. DirectPlay is a high-level software interface between applications and communication services that makes it easy to connect games over the Internet, a modem link, or a network.

DirectPlay 4: A programming library that implements the IDirectPlay4 programming interface. DirectPlay 4 provides peer-to-peer session-layer services to applications, including session lifetime management, data management, and media abstraction. DirectPlay 4 first shipped with the DirectX 6 multimedia toolkit. Later versions continued to ship up to, and including, DirectX 9. DirectPlay 4 was subsequently deprecated. The DirectPlay 4 DLL continues to ship in current versions of Windows operating systems, but the development library is no longer shipping in Microsoft development tools and software development kits (SDKs).

DirectPlay 8 protocol: The DirectPlay 8 protocol is used by multiplayer games to perform low-latency communication between two or more computers.

DirectPlay 8 server application: A DirectPlay 8 application that is hosting a DirectPlay 8 session. When connected, the actual communication between nodes in a DirectPlay 8 session may be client/server or peer to peer. The term "server" in this definition is meant to indicate the role that the DirectPlay 8 server application is taking in the host enumeration process, which is the DirectPlay 8 application that is currently hosting a DirectPlay 8 session.

DirectPlay host: The player in a DirectPlay peer-to-peer game session that is responsible for performing game session management duties, such as responding to game session enumeration requests and maintaining the master copy of all the player and group lists for the game. It has connections to all DirectPlay peers in the game session.

DirectPlay Name Server (DPNSVR): A forwarding service for enumeration requests that eliminates problems caused by conflicts between port usages for multiple DirectPlay applications.

DirectPlay protocol: Refers to either the DirectPlay 4 or the DirectPlay 8 protocol.

DirectX: Microsoft DirectX is a collection of application programming interfaces for handling tasks related to multimedia, especially game programming and video, on Microsoft platforms.

DirectX Diagnostic (DXDiag): DXDiag.exe is an application that uses the DirectPlay DXDiag Usage Protocol [MS-DPDX] traffic.

DirectX runtime: A set of libraries created for the family of Windows operating systems that provide interfaces to ease the development of video games.

DPNID: A 32-bit identification value assigned to a DirectPlay player as part of its participation in a DirectPlay game session.

game: An application that uses a DirectPlay protocol to communicate between computers.

game session: The metadata associated with the collection of computers participating in a single instance of a computer game.

globally unique identifier (GUID): A term used interchangeably with universally unique identifier (UUID) in Microsoft protocol technical documents (TDs). Interchanging the usage of these terms does not imply or require a specific algorithm or mechanism to generate the value. Specifically, the use of this term does not imply or require that the algorithms described in [RFC4122] or [C706] must be used for generating the GUID. See also universally unique identifier (UUID).

group: A named collection of users who share similar access permissions or roles.

host: In DirectPlay, the computer responsible for responding to DirectPlay game session enumeration requests and maintaining the master copy of all the player and group lists for the game. One computer is designated as the host of the DirectPlay game session. All other participants in the DirectPlay game session are called peers. However, in peer-to-peer mode the name table entry representing the host of the session is also marked as a peer.

host migration: The protocol-specific procedure that occurs when the DirectPlay peer that is designated as the host or voice server leaves the DirectPlay game or voice session and another peer assumes that role.

instance: A specific occurrence of a game running in a game session. A game application process or module may be created more than one time on a single computer system, or on separate computer systems. Each time a game application process or module is created, the occurrence is considered to be a separate instance.

Internet Protocol security (IPsec): A framework of open standards for ensuring private, secure communications over Internet Protocol (IP) networks through the use of cryptographic security services. IPsec supports network-level peer authentication, data origin authentication, data integrity, data confidentiality (encryption), and replay protection.

Internet Protocol version 4 (IPv4): An Internet protocol that has 32-bit source and destination addresses. IPv4 is the predecessor of IPv6.

Internet Protocol version 6 (IPv6): A revised version of the Internet Protocol (IP) designed to address growth on the Internet. Improvements include a 128-bit IP address size, expanded routing capabilities, and support for authentication and privacy.

Internetwork Packet Exchange (IPX): A protocol that provides connectionless datagram delivery of messages. See [IPX].

little-endian: Multiple-byte values that are byte-ordered with the least significant byte stored in the memory location with the lowest address.

local area network (LAN): A group of computers and other devices dispersed over a relatively limited area and connected by a communications link that enables any device to interact with any other device on the network.

modem link (or modem transport): Running the DXDiag application over a modem-to-modem link. See Also, serial link.

name table: The list of systems participating in a DXDiag, DirectPlay 4, or DirectPlay 8 session, as well as any application-created groups.

name table entry: The DN_NAMETABLE_MEMBERSHIP_INFO structure ([MS-DPDX] section 2.2.33) along with associated strings and data buffers for an individual participant in the DXDiag session. These could be considered players.

network address translation (NAT): The process of converting between IP addresses used within an intranet, or other private network, and Internet IP addresses.

network byte order: The order in which the bytes of a multiple-byte number are transmitted on a network, most significant byte first (in big-endian storage). This may or may not match the order in which numbers are normally stored in memory for a particular processor.

partner: A computer connected to a local computer through either inbound or outbound connections.

payload: The data that is transported to and from the application that is using either the DirectPlay 4 protocol or DirectPlay 8 protocol.

peer: In DirectPlay, a player within a DirectPlay game session that has an established connection with every other peer in the game session, and which is not performing game session management duties. The participant that is managing the game session is called the host.

peer-to-peer: A server-less networking technology that allows several participating network devices to share resources and communicate directly with each other.

peer-to-peer mode: A game-playing mode that consists of multiple peers. Each peer has a connection to all other peers in the DirectPlay game session. If there are N peers in the game session, each peer has N–1 connections.

player: A person who is playing a computer game. There can be multiple players on a computer participating in any given game session. See also name table.

poll packet (POLL): A packet in which the sender has set the PACKET_COMMAND_POLL bit in the packet header ([MS-DPDX] section 2.2.16). POLL indicates that the receiver must immediately acknowledge receipt of the packet when it arrives.

round-trip time (RTT): The time that it takes a packet to be sent to a remote partner and for that partner's acknowledgment to arrive at the original sender. This is a measurement of latency between partners.

selective acknowledgment (SACK): A cumulative mechanism that indicates successful receipt of packets beyond the next receive indicator. Next receive reports all packets prior to when its sequence ID has been received, but subsequent packets can arrive out of order or with gaps in the sequence. SACK masks enable the receiver to acknowledge these packets so that they do not have to be retried, in addition to the packets that were truly lost. See also acknowledgment (ACK), next receive, and next send.

send mask: A bitmask mechanism indicating that previously sent packets might have been dropped, were not marked as reliable, and will never be retried.

sequence ID: A monotonically increasing 8-bit identifier for packets. This is typically represented as a field named bSeq in packet structures.

serial link (or serial transport): Running the DXDiag application over a null modem cable connecting two computers. See also modem link.

server: A DirectPlay system application that is hosting a DirectPlay game session. In the context of DirectPlay 8, the term is reserved for hosts using client/server mode.

session packet: A session packet is associated with client/server session management. A session packet begins with a zero byte and is used for locating sessions and testing network paths. See transport packet.

tick count: In DirectPlay, the count from when the system was booted, in milliseconds.

transport layer: The fourth layer in the Open Systems Interconnection (OSI) architectural model as defined by the International Organization for Standardization (ISO). The transport layer provides for transfer correctness, data recovery, and flow control. The transport layer responds to service requests from the session layer and issues service requests to the network layer.

transport packet: A transport packet has a nonzero first byte and is further divided into command, user data, and acknowledgment packet types. See session packet.

Unicode: A character encoding standard developed by the Unicode Consortium that represents almost all of the written languages of the world. The Unicode standard [UNICODE5.0.0/2007] provides three forms (UTF-8, UTF-16, and UTF-32) and seven schemes (UTF-8, UTF-16, UTF-16 BE, UTF-16 LE, UTF-32, UTF-32 LE, and UTF-32 BE).

User Datagram Protocol (UDP): The connectionless protocol within TCP/IP that corresponds to the transport layer in the ISO/OSI reference model.

wide characters: Characters represented by a 2-byte value that are encoded using Unicode UTF-16. Unless otherwise stated, no range restrictions apply.

MAY, SHOULD, MUST, SHOULD NOT, MUST NOT: These terms (in all caps) are used as defined in [RFC2119]. All statements of optional behavior use either MAY, SHOULD, or SHOULD NOT.