H.323 Fast Connect and Versioning

Paul E. Jones paulej at packetizer.com
Mon Oct 20 22:43:46 EDT 2003


Time permitting, I will probably try to take something to the TIA TR30.5
meeting.  I may not write a concrete proposal, but just present the problem
formally and propose a few alternatives.  Perhaps through the discussion, we
may end up with something we can take to the ITU.  Will you be present at
that meeting?


----- Original Message ----- 
From: "Hiroshi Tamura" <tamura at toda.ricoh.co.jp>
To: <paulej at packetizer.com>
Cc: <tamura at toda.ricoh.co.jp>; <PeterP at vegastream.com>;
<itu-sg16 at external.cisco.com>; <tsg16q14 at itu.int>
Sent: Monday, October 20, 2003 10:13 PM
Subject: Re: H.323 Fast Connect and Versioning

> Paul,
> Thanks for your explanation.
> It seems that I did not notice the important points.
> I quote them for other members.
> ---------------------------------------------------------
> in H.323 (regarding fast connect procedure)
> ...
> A called endpoint may choose to repeat the fastStart element in all
> messages up to and including Connect: the contents of the fastStart
> shall be the same.
> ...
> NOTE - The called endpoint is only allowed to alter fields in a proposed
> OpenLogicalChannel structure as specified in this clause. An endpoint is
> allowed, for example, to alter the number of frames per packet or other
> characteristics of the proposed channel not specifically stated in this
> ---------------------------------------------------------
> > the Called Device.  The problem is really the fault of the Called
> > because it accepted a version it did not support.  However, the reason
> > a called device would do this is because there is nothing in Annex
> > or Annex B/T.38 that tells the called endpoint not to accept the
> > proposal or to modify the version to match the actual supported version
> > the endpoint.
> OK. I understand.
> > Probably the best solution would be to modify the T.38 and Annex D/H.323
> > text to allow the following:
> >
> >   Calling Device                         Called Device
> >     (Version 3)                           (Version 0)
> >    Setup(fastStart(T38Version=3))-------------->
> >    <------------------------------------Connect(fastStart(T38Version=0)
> >                                                                     ^^^
> >                                                                      |
> >     Responds with actual supported Version----------------------------
> Yes.
> > Also, note that we have precisely the same problem with SIP, too.  The
> > INVITE message and the 200 message looks almost exactly the same.
> > as far as I know, does it say how a SIP device should handle the T.38
> > version field when replying to an INVITE.
> As there are no SIP devices for T.38 fortunately, we should handle soon.
> Anyway, we should discuss and decide at the next SG16 meeting.
> Do you plan to propose something at TIA TR30.5 meeting in December?
> Best regards,
> --
> Hiroshi Tamura

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