What is H.323?

The article is about the H.323 protocol that describes the transmisson of audio and video data. Have more information about the protocol, get an insight how a H.323 call is set up with the help of a picture and learn what the elements of H.323 are.

H.323 is an ITU (International Telecommunication Union) VoIP protocol. It is a base for audio, video and also data communication via the Internet. It is applied by service providers for audio and video services in real-time applications. VoIP traffic is transmitted through H.323 networks.

A H.323 call

A H.323 call can be set up like this: a VoIP phone starts communication with the help of a gateway through the Ozeki Phone System XE and the gateway connects the initiated call with the called end-point, another VoIP phone. This process can be seen in the following picture (Figure 1):

what is h323
Figure 1 - What is H323?

The H.323 system describes different network elements that are supposed to work together to be able to send multimedia (audio, video) communication capabilities. These elements can be different terminals, multipoint control units, gateways, gatekeepers etc that are also called endpoints. To build up communication at least two terminals are needed.

H.323 elements

  • Terminals: they are key elements in the communication process. Terminals can be IP/ VoIP phones or video-conferencing systems.

  • Multipoint Control Units: they handle multipoint conferences and consist of 2 elements (MCU and MP). MCU is responsible for mixing and switching video and with the help of this, video calls are also possible to make.

  • Gateways: they are such devices (servers) that make communication possible between H.323 and another network, like PSTN or ISDN.

  • Gatekeepers: they are optional elements in H.323 network and offers several different services like end-point registration, address solution, admission control etc.

Ozeki Phone System serves as a great option for exploiting the functionalities of VoIP technology. Ozeki Phone System uses H.323 protocol to deliver rich multimedia (both video and audio) communication.

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What is H.323? (Video tutorial)

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