H.323 Protocol Overview

Protocol Standard

The H.323 protocol is an International Telecommunication Union (ITU-T) standard that describes transmission for packet-based video, audio, and data conferencing. The current ITU-T recommendation, known as Version 2.0, was ratified by Study Group 16 of the Telecommunications Sector. H.323 is an umbrella standard that refers to these other standards:

The H.225.0 standard includes the following:

Q.931 for call signaling (setup, teardown)

RAS for Registration, Admission, and Status

RTP/RTCP for media stream packetization and synchronization

H.235 for security

H.245 for call control (capabilities, master/slave, logical channel)

H.261 and H.263 video codecs

H.450 for supplementary services

G.711, G.728, G.729, G.723 audio codecs

Allows Multimedia

The H.323 protocol is used for multimedia (audio, video, and data) conferencing over packet networks. The goal of H.323 is to allow multimedia communication devices to interoperate regardless of the type of network those devices are connected to.

H.323 in Packet Networks

H.323 can be used on top of any packet network transport layer, such as Ethernet, IP/TCP/UDP, ATM, and Frame Relay. H.323 uses the Internet Protocol (IP) for internetwork conferencing.