An ITU standard for real-time voice and videoconferencing over packet networks, including LANs, WANs and the Internet. Although H.323 is a very comprehensive standard that supports voice, video, data, application sharing and whiteboarding, the parts relating to audio protocols have been widely used for IP telephony applications.
H.323 defines various elements including media gateways for conversion to packets, gatekeepers for call control and multipoint control units (MCUs) for conferencing. Following are the various protocols referenced under the H.323 umbrella. See
videoconferencing,
codec,
H.225,
H.245,
IP telephony,
gatekeeper,
SIP and
MGCP/MEGACO.
Standard Function
G.711 Audio codec
G.722 Audio codec
G.723 Audio codec
G.728 Audio codec
G.729 Audio codec
H.261 Video codec
H.263 Video codec
H.264 Video codec
H.225 Call control
H.245 Control messages
Q.931 Connection messages
RAS Control channel
T.120 Data collaboration