H.323 is a protocol used for transmission of real-time video and audio data over a packet-switched network like Internet Protocol. It is a protocol standard for multimedia communications. H.323 protocol is maintained by the Study Group 16 within the ITU (International Telecommunication Union) Telecommunication Standardization Sector, also known as ITU-T. Most VoIP application utilizes H.323 protocol, since it supports call forwarding, call setup and teardown. A key feature of H.323 protocol is QoS (Quality of Service), which allows traffic management and real-time prioritization to be placed over Ethernet. Apart from packet switched network, it also supports multimedia communications over Public Switched Telephone Network (PSTN), 3G mobile networks and Integrated Service Digital Network (ISDN).
In 1996, International Telecommunication Union (ITU) published the first version of H.323 with an importance of enabling videoconferencing over a LAN (Local Area Network). It was quickly implemented by the companies over an IP network (including WAN) as a means of transmitting audio communication. In 1998, a new title “Packet-Based Multimedia System” was given to H.323. In 2006, the current version of H.323 was referred as H.323v6.
Protocols used in H.323 systems are –
• H.225.0 RAS (Registration, Admission and Status) to provide admission control services and address resolution between a Gatekeeper and H.323 endpoint.
• H.225.0 Call Signaling to establish communication with the remote entity.
• H.235 for security of media and signaling.
• H.239 for live videos, images and videoconferencing.
• H.245 control protocol for multimedia communication.
• H.450 for various supplementary services.
• H.460 for Firewall traversal (FW) and Network Address Translation (NAT).
• RTP (Real-time Transport Protocol) for...