Glossary

H.323 is an “umbrella” Recommendation by ITU-T , defining protocols that support multimedia communication sessions over packet networks. H.323 provides means for call signaling and control, media transport and control and bandwidth control for both peer-to-peer and multi-party sessions.

H.323 was published in November 1996, focusing mainly on video conferencing over LAN, but was quickly adopted by the industry as a means for voice (and later video) communication over IP networks, including WAN and the public Internet.

H.323 has been revised and republished, with many enhancements and improvements. In 1998 the title of the Recommendation changed to “Packet-Based Multimedia Communication Systems”. The latest version, H.323v7, was published in December 2009.

H.323 defines four primary entities, which may be co-located:

• Terminals - provide user interface for real-time, two-way communication
• Gateways - interface between H.323 networks and other networks
• Multipoint Conferencing Units (MCUs) - allow three or more endpoints to participate in a multipoint conference
• Gatekeeper - provides call control functionality within an H.323 zone by managing the other entities as well as their authentication and usage of network resources and services

Related links

• H.323 community
• H.323 protocol stack
• H.323 specification
• H.323 Forum