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H.323 Definition
H.323 standard is defined by the International Telecommunication Union (ITU), which states that the protocols to provide audio-visual communication sessions on packet switched network.
The H.323 standard addresses call signaling and control, multimedia transport and control, and bandwidth control for point-to-point and multi-point conferences.
It is widely implemented by voice and videoconferencing equipment manufacturers, is used within various Internet real-time applications such as VoIP, Video conferencing over IP.
H.323 is now considered to be the standard for interoperability in audio, video and data transmissions as well as Internet phone and voice-over-IP because it addresses call control and management for both point-to-point and multipoint conferences as well as gateway administration of media traffic, bandwidth and user participation.
What are H.323 Components?
Terminals
Terminals are the client endpoints on the LAN that provide real-time bidirectional multimedia communications. An H.323 terminal can either be a personal computer (PC) or a stand-alone device, running an H.323 stack and the multimedia applications.
It supports audio, video and data communications. H.323 specifies the modes of operation required for different audio, video and/or data terminals to work together.
H.323 terminal plays a key role in IP-telephony services, and is the dominant standard of the next generation of Internet phones, audio conferencing terminals, and video conferencing technologies.
Gateways
A gateway connects two or more networks. An H.323 gateway provides connectivity between an H.323 network and a non-H.323 network.
For example, a gateway can connect and provide communication between an H.323 terminal and TDM networks (Time Division Multiplexing networks include all switched telephony networks, e.g., PBX, public switched telephone network [PSTN]).
The connectivity of dissimilar networks is achieved by translating protocols for call setup and release, converting media formats between different networks, and transferring information between the networks connected by the gateway.
For example, in the case of video conferencing a gateway may be required to call H.323 end point or VC in remote site and also to call a VC in remote end point on ISDN. Basically gateways convert TDM traffic to IP packets.
Gatekeepers
The gatekeeper is the most important H.323 components. The gatekeeper’s primary job is to act as the central point for all calls within its zone and provide call control services for registered H.323 endpoints.
Basic function of the gatekeeper is address translation, Calls originating within an H.323 network may use an alias to address the destination terminal. Calls originating outside the H.323 network and received by a gateway may use an E.164 telephone number to address the destination terminal.
The gatekeeper must be able to translate the alias or the E.164 telephone number into the network address for the destination terminal. The destination endpoint can be reached using the network address on the H.323 network. The translation is done using a translation table that is updated with Registration messages.
For example in Voice over IP which is driving voice traffic over IP network, we dial the extension number of the remote IP phone. IP network only handles IP not decimal numbers, because we cannot remember IP address of remote equipment we are dialing by number.
This conversion of decimal numbers to IP address and IP address to decimal number is done by gatekeeper. Besides these function gatekeeper also does Admission Control, Bandwidth Control, and Zone Management.
About the Author
Author is a telecom professional having vast knowledge and experience in converged network. For more information please visit this website “www.voicevideodatablog.com”
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