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Question 2/16 – H.323 real-time multimedia system
(Continuation of Questions 2/16 and 5/16)


ITU-T Recommendation H.323 is the most widely used communication protocol supporting audio, video, and data collaboration over packet-based networks. Typical applications of H.323 are audio and video conferencing, which improves communication quality and efficiency and contributes to reduction of greenhouse gas emission by reducing the need for travel. Its utility includes the Internet, private global networks, corporate LANs, and corporate WANs. While it may operate over a variety of transports, H.323 is almost exclusively used only on IP networks. This has not limited the use of H.323. In fact, H.323 is successfully used for communication between users over wired and wireless links, including satellite and microwave links.

In the last study period (2005-2008), this work focused on, among other things, robustness, interworking with SS7 and other networks, quality of service, and NAT and firewall traversal. Particularly for the NAT and firewall traversal issue, a series of Recommendations codified robust solutions that will make the deployment of H.323 multimedia communication easy for service providers, enterprises, and home users, especially in light of increased security requirements and the increasing deployment of H.323 multimedia applications.

There is a continued focus on maturing the protocol, adding functional capability where vendors and service providers identify a need for specific enhancements to the base protocol or extension thereto.

Study items

Study items to be considered include, but are not limited to:

  • Ongoing work in H.225.0, H.245, H.246, H.249, H.323, H.332, H.341, H.450.x and H.460.x
  • Identification of changes or additions to H.323 for operation over NGN
  • Increase accessibility features for the H.323 multimedia conferencing systems
  • Consideration of the use of H.323 within the context of broadcast systems
  • NAT and firewall traversal
  • Standardizing the means for interworking between H.323 systems and other systems, including the legacy telephone network and advanced multimedia system, through additions to Recommendation H.246 and other Recommendations as necessary. A particular focus will be H.323 – SIP interworking
  • Considerations on how to help measure and mitigate climate change


Tasks include, but are not limited to:

  • New and enhanced feature development
  • Produce additional extensions to the H.323 protocol through the addition of H.450-series and H.460-series Recommendations
  • Enhance H.323 system to align it with the NGN architecture
  • Define the requirements and the procedures for interworking between H.323 and SIP
  • Produce amendments to and/or new revisions of H.225.0, H.235-series, H.245, H.246, H.249, H.323, H.332, H.341, H.450 sub-series, and H.460 sub-series, H.501 and H-series Supplement 4

An up-to-date status of work under this Question is found in the SG 16 work programme (




  • Q.931, G.700-series audio codecs, H.260-series video codecs, H.300-series systems, X.680


  • 1, 4, 6, 7, 9, 10, 14, 21, 22, 26/16

Study Groups:

  • ITU-T SG 2 for service aspects and human factors
  • ITU-T SG 11 for signalling
  • ITU-T SG 12 for quality aspects
  • ITU-T SG 13 for future networks aspects, in particular NGN aspects
  • ITU-T SG 15 for transport aspects
  • ITU-T SG 17 for security and ASN.1

Other Bodies:

  • ISO/IEC JTC1/SC29/WG11 for MPEG aspects
  • IMTC for interoperability aspects and enhancements to existing Recommendations


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Updated : 2008-12-05