H.323 is the ITU-T's standard, which was originally developed for multimedia conferencing on LANs but was later extended to cover Voice over IP. The standard encompasses both point-to-point communications and multipoint conferences. H.323 defines four logical components: Terminals, Gateways, Gatekeepers and Multipoint Control Units (MCUs). Terminals, gateways and MCUs are known as endpoints. The ITU-T H.323 protocol supports a distributed VOIP Network architecture.
H.323 Network Elements
- Terminals: a network endpoint which may provide audio, data and video, communications with another H.323 terminal.
- Gateways: a network function that provides access to terminals on a circuit switched network (such as the PSTN) or another H.323 network.
- Gatekeepers: a network function that provides address translation, access control, bandwidth management, and other management operations.
- Multipoint Control Units: a network function that allows three or more terminals to participate in a multipoint conference.
Main ITU-T H.323 Standards
| Standard# | Description |
| H.323 | An umbrella recommendation from the ITU-T that defines the protocols to provide audio-visual communication sessions on any packet network. |
| H.225.0 | A protocol for call signaling, the media (audio and video), the stream packetization, media stream synchronization and control message formats. |
| H.235 | For security in H.323 network. |
| H.239 | For dual stream use in videoconferencing. |
| H.245 | A control protocol for multimedia communication |
| H.246 | H.323/PSTN Interworking |
| H.350 | Directory Services Architecture for Multimedia Conferencing |
| H.360 | An architecture for end-to-end QoS control and signaling |
| H.450 | For supplementary services such as call waiting, call forwarding, etc. |
| H.460.x | Supplements in H.323 |
| H.501 | Protocol for mobility management and intra/inter-domain communication in multimedia systems |
| H.510 | Mobility for H.323 multimedia systems |
H.323 Architecture
Related Terms: H.323
Reference Links: http://www.javvin.com/protocolVOIP.html: VOIP Protocols