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H.323 definition

H.323 is a set of protocols and standards for audio, video, and data communication over the internet in real time (such as phone and video calls). Developed by the International Telecommunication Union (ITU), H.323 covers various aspects of audio and video communication — from call setup to network management.

See also: communication protocol

How does H.323 work?

  • When two devices want to start an audio or video call, H.323 sends a signal to help them find each other on the network.
  • H.323 uses a signaling protocol (like H.225) to exchange messages with information about the communication type, how to compress audio/video, and other parameters.
  • H.323 uses the RTP for sending and receiving real-time audio and video data.
  • When the call is complete, H.323 devices exchange signaling messages to end the session gracefully.

History of H.323

  • Early 1990s. As the internet was growing, there was a need for standards to enable real-time audio and video communication. In the early 1990s, the International Telecommunication Union (ITU) began working on establishing these protocols.
  • 1990-2000. The first, second, and third versions of the H.323 protocol were released in the first ten years of its existence. Each version brought further improvements and additional features to the previous versions.
  • Recent years. H.323 continued to evolve with subsequent versions, addressing security concerns, enhancing video and audio quality, and adapting to changing network environments. However, it began facing competition from other protocols, such as SIP, which gained popularity in voice and video communication applications.
  • Today. H.323 remains used in video conferencing systems, especially in corporate and government settings. However, SIP and other communication protocols have replaced it in many contexts (like telephony services and consumer video calling apps).