H.323 Annex D

[Paul Long]

Paul,

H.323v3 requires H.245v5, not H.245v3.

Summary/H.323v3: "Version 3 products can be identified by H.225.0 messages
containing a protocolIdentifier = {itu-t (0) recommendation (0) h (8) 2250
version (0) 3} and H.245 messages containing a protocolIdentifier = {itu-t
(0) recommendation (0) h (8) 245 version (0) 5}."
    and
Summary/H.323v3: "Support of H.225.0 (1999) and H.245 (1999 or later) as
identified in messages above, shall be the singular requirement and
definition of H.323 systems which are H.323 Version 3 compliant."

Interesting... Note that the second passage conflicts with the first in that
the second says that H.245v5 "or later" shall be used but the first passage
says that H.245v5 _only_ shall be used with H.323v3. Which is it? IMO, we'll
run into even more interoperability problems by decoupling H.245 versions
from H.323 versions. Also, H.323v2 (1998) is Decided, so it cannot be
modified to allow other versions of H.245.

Paul Long
Smith Micro Software, Inc.

-----Original Message-----
From: Paul E. Jones [mailto:paul.jones at TIES.ITU.INT]
Sent: Sunday, February 27, 2000 12:47 AM
To: ITU-SG16 at MAILBAG.INTEL.COM
Subject: Re: H.323 Annex D


Francois,

By default, I believe that editor would be me.  This annex was intended
to work with H.323v2 systems and later, but you are correct that there
was no way to specify T.38 until H.245v4.

Of course, H.323v2 systems used H.245v3.  H.323v3 systems used H.245v3
or higher (the key element).  So, I suppose the question is: is H.323v3
required?  Surely not, as there are implementations out there.  We have
argued about whether H.323v2 systems could use later versions of H.245.
The outcome was "no"-- perhaps that needs to be revisited.

There have been recent changes to H.245 ASN.1 to support T.38.  At least
there have been some proposed changes.  Unfortunately, I missed much of
that discussion.  The meeting report says that those changes were added
to H.245v6.

Mike, is it true that the T.38-related changes from H.245v4 to H.245v6
were nothing more than additions to H.245-- not "changes", per se.
Also, did the proposed changes (from TD8/WP2, I believe) make it into
H.245v6?

As for Annex D, I am considering just pulling that into the H.323
document, rather than keeping it as a separately published annex-- does
anybody object to that?  That would certainly address questions related
to references going forward.  However, we need to reach a decision about
the current publication.  I suspect we need something for the IG, but
the problem is that H.323v2 is "old news" now.  What to do....

Paul