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H323

H.323 is an international ITU standard for voice, data and video communication over packet-oriented networks that specifies the specific capabilities of end devices in the IP environment. H.323, which is functionally comparable to the Session Initiation Protocol( SIP), was developed for the transmission of multimedia applications and forms the basis for VoIP and video-over-IP.

The H.323 standard is used to define real-time communication in LANs that cannot provide guaranteed quality of service. It consists of several protocols for signaling, exchange of terminal functionality, connection control, exchange of status information and data flow control. The standard has been revised several times and in its third version defines the transmission of features.

Video conferencing standards of the ITU

Video conferencing standards of the ITU

The multimedia standard recognizes three different signaling functions between the H.245 control channel, the Q.931 signaling channel, and the RAS channel, Registration, Admission, and Status (RAS).

H.323 structural model

H.323 structural model

The standard is derived from the H.320 multimedia standard for ISDN. It has defined network transitions between ISDN and ATM and guarantees interoperability among vendor products, with four main groups defined: H.323 gateways, gatekeepers, terminals and multipoint control units( MCU).

For Internet telephony, the gatekeeper is the most important component because it includes the necessary software for the management of so-called zones and call services.

Informations:
Englisch: H323
Updated at: 03.10.2020
#Words: 207
Links: international telecommunication union (ITU), standard (STD), data, video, communication (COM)
Translations: DE
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