[sg16-avd] Recent progress in H.323 and H.325
Paul E. Jones
paulej at packetizer.com
Tue Sep 17 16:40:35 EDT 2013
For the benefit of those who have not attended SG16 meetings recently, I
want to share some of the more exciting work the group is doing in the area
of IP-based multimedia communications (IPMC). Specifically, this message is
focused on H.323 and H.325 (AMS) work.
The work on H.325 has been moving forward slowly, partly due to changes in
peoples' priorities due to the global economic crisis, but also do to
challenges with finding the right path forward. The vision for what H.325
will enable has not substantially changed, but we had to find a way to
realize that vision in a way that can actually be easily implemented.
In recent meetings, I think that's starting to become clearer with new
concepts being introduced in H.323 called "Assets". An Asset is a an
application that implements a subset of the H.225.0 and H.245 protocols to
provide a very specific function (or set of functions), such as an
electronic whiteboard, file transfer, or application sharing. Each
application type will be defined in its own Asset application specification.
At a high level, the user's terminal and an Asset associate with each other
using call-independent supplementary service messages, which are a type of
message already defined and supported in H.323. In this way, we do not
introduce new message types and messages will work over the existing H.323
infrastructure. Once devices are associated, they can be queried, invoked,
and terminated using similar message constructs.
Assets themselves register with the Gatekeeper as a "Simple Endpoint Type"
(SET). Presently, H.323 defines two SET device types, so Assets will be a
third type of SET.
During the IMTC meeting that will be held in Portugal next month
(http://imtc.org/forum2013/agenda.html), Spranto (http://www.spranto.com)
will be there providing a live demonstration of the H.323 Asset concept.
Not only that, but it will be a demonstration working through NAT/FW
devices. This should be really interesting since, in my opinion, this
represents the next-step in multimedia communications by bringing together a
plurality of devices and applications to provide for a richer user
In parallel, we are now modeling the same approach in H.325. We're defining
the H.325 signaling messages, working to ensure that we keep the number of
message primitives to a minimum and to reduce the complexity of every
entity. We also decided to switch to using JSON for signaling in H.325,
which should be very interesting to developers. It should make it easier to
build a web-based H.325 application, but it is also much easier to explain
the protocol, extend it, etc. JSON has proven to be a very flexible and
If you are interested in getting involved either the H.323 Asset work or the
H.325 work, feel free to reach out to me. I've have been neglectful of the
H.325 design mailing list for a while now, I know, due to my other
priorities preempting a lot of my direct involvement. However, I would very
much like to re-start the interim electronic meetings on H.325 if there is
interest. We can do that following the upcoming SG16 meeting (28 October -
8 November). Just let me know and I'll make plans accordingly.
In the meantime, I would definitely encourage you to try to make it to the
IMTC meeting to see some of this new stuff in action.
Paul E. Jones
Rapportuer, ITU-T Q2/SG16
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