H.323 is the international standard for multimedia communication over packet-switched networks, including LANs, WANs, and the Internet. It was first defined by the ITU in 1996 and has been updated regularly. The most recent version is H.323 version 7 (2009).

H.323 is an "umbrella" specification, which includes the standards H.323, H.225.0, H.245, the H.450-series documents, and the H.460-series. It allows for the use of T.120 for data collaboration and file transfer. When referring to the system and set of documents, people generally refer to "H.323", though not every document is mandatory as part of a standard H.323 system. For example, H.460.2, which describes number portability, is generally not used in enterprise videoconferencing systems.

The scope of H.323 covers real-time voice, video, and data communication over packet-switched networks. It was designd from the outset to operate over IP networks, primarily, though H.323 may also operate over other packet-switched networks. It was designed with multipoint voice and video conferencing capabilities, though most users do not take advantage of the multipoint capabilities specified in the protocol.

H.323 was the world market leader for transporting voice and video Voice over IP and video networks around the world, with literally billions of minutes of voice traffic every month alone.

Today, H.323 is primarily used in enterprise videoconferencing equipment used for communicating with people across the organization, as well as around the world using real-time video. Popular telepresence systems often utilize H.323, for example.

Resources: H.323 Information Site, H.323 Forum, VoIP Information Site

See Also: Voice over IP (VoIP), Session Initiation Protocol (SIP), H.248 (or Megaco), Media Gateway Control Protocol (MGCP)