On TD26 - Fast TCS and M/S negotiation in H.323v4

Dave Walker drwalker at ss8networks.com
Thu Jun 1 14:48:57 EDT 2000

I'm not sure this is correct.  H.323 section 7.3.1 mandates the use of
Q.931 Annex D procedures.  In turn, that Annex uses Q.931 clause 5.
So *that* is what applies in the absence of any overriding provisions
in H.323.  So I think that Q.931/ *should* apply.

But to re-iterate what Paul asked earlier, if we had a description of
the problem that this was intended to solve, perhaps a less contentious
solution could be found.


Dave Walker
SS8 Networks
Ottawa, Canada

> Francois Audet wrote:
> Except that the section that Paul quotes is in Q.931 and NOT in H.225.0.
> It has nothing to do with H.225.0. In fact, it talks about a message
> that is not even supported in H.225.0 (i.e., RELEASE).
> To reiterate: H.323v2 does not describe how an endpoint receiving both
> elements shall behave themselves. It just says that the sender shall not
> include both since it would cancel fast start. This particular case (wich
> apparently is not supported by any implementation) would result (if you
> follow the logic of H.323v2) in ignoring fast start and proceeding with
> H.245 tunnelling. That is NOT a backward compatibility problem, and it
> does't break anything.
> Rejecting the call with cause value 100 is definitively NOT what H.323v2 says.
> > In Q.931, the user-user IE is typically optional, so the clause that
> > Paul Long's been quoting wouldn't apply.  However, since H.323 makes
> > the UUIE mandatory, it *does* apply in the case under discussion.
> > I think that the statement contained in TD-26, that it preserves
> > backwards compatibility, is completely wrong.  The correct statement
> > should have been that it doesn't break implementations known to the
> > authors.  I agree with Paul that we should try to develop a better
> > solution.
> >
> >

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