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H.323 Version 5 Approved

August 11, 2003

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As many of you may already know, H.323 version 5 was officially approved at the end of July 2003. Unlike previous revisions of the Recommendation, H.323 version 5 aimed to maintain stability in the protocol by introducing only modest additions to the base protocol, rather than introducing sweeping changes as was the case in prior revisions. Look to version 5 as "maintenance" release of H.323 version 4, with just a few new fields added and only one new message type.

Of course, standardization activities surrounding H.323 are still quite active. Most of the new enhancements to H.323 have been introduced through the "Generic Extensibility Framework" (GEF) that was introduced in H.323 version 4. Since the approval of H.323 version 4 in 2000, we have added 9 new features to H.323 which utilize GEF. What's nice about GEF is that we are now able to add new features to H.323 without altering the base protocol. People have asked for stability and this is one step in that direction.

Some of the new additions to H.323 since version 4 include:

  • Annex M.3 - Tunneling of DSS1 signaling within H.323 systems
  • Annex O - Defines how to use the H.323 URL and other DNS services within the context of H.323 systems
  • Annex P - Describes how to do modem relay within H.323 systems
  • Annex Q - Far-end camera control for video conferences
  • Annex R - Provides for fault tolerance— calls do not drop when a single intermediate signaling entity, such as a softswitch, fails while the calls are in progress. (GEF)
  • H.460.1 - Overview of the Generic Extensibility Framework and "author's guide"
  • H.460.2 - Number portability (GEF)
  • H.460.3 - Circuit Status Map (GEF)
  • H.460.4 - Call priority designation (GEF)
  • H.460.5 - Transport of duplicate Q.931 IEs (GEF)
  • H.460.6 - Extended Fast Connect (GEF)
  • H.460.7 - Digit maps (GEF)
  • H.460.8 - Querying for alternate routes (GEF)
  • H.460.9 - QoS monitoring and reporting (GEF)

As you can see, virtually all of the new enhancements utilize the GEF. In fact, the entire H.460.x series of documents are devoted to adding enhancements to H.323 via the GEF. Developers can pick and choose which of the GEF enhancements to support in their products.

A lot of work has gone into enhancing the H.323 version 5 protocol and post-v4 additions. There are still a number of on-going activities, so look to see additional H.460.x documents in the future.

From time to time, Packetizer is asked about the status of H.323 in the industry. As most of you know, H.323 is the only IP-based communication protocol that fully defines the usage of video and data collaboration tools. For video conferencing applications, H.323 "owns" that market without a doubt. The ITU has reported that, as has been the case nearly every year for several years, H.323 was once again the #1 downloaded standards document from the ITU web site. There is a lot of interest from new developers.

Traffic statistics are hard to find, and Packetizer would love to get some official numbers from service providers, but it is well-known that the largest VoIP networks in the world are running H.323. Companies like ITXC and China Unicom are carrying millions of minutes of traffic every month. Unconfirmed reports say that some traffic estimates actually range around 1 billion minutes of traffic each month. The H.323 Forum reports that there are nine service providers that have carried over 1 billion minutes to date. Based on other reports, we suspect those numbers are "several billion" now.