Yes, a few comments:
1 It seems that all current implementations that we could think of
  would simply ignore the tunnelling information if the fastStart
  element is present. This means, that there would be no
  interoperability problems. Fast start would be sucessfull, but not
  tunnelling, which would mean that tunnelling would have to happen
  after the SETUP message, as per H.323v2 and v3.
2 There is a small possibility that an implementation would acutally
  give priority to the tunnelling information instead of the fastStart
  element (v2 and v3 don't say what would happen if they are present, they
  just say not to do it). In that particular case, the fastStart would fail
  but the tunnelling would be successful. So the worst case scenario is that
  fastStart fails, but "fast tunnelling" is successful. This doesn't seem to
  me to be a real interoperability problem. In any case, it seems that case
  1 is much more likely.

> -----Original Message-----
> From: Paul E. Jones [mailto:paulej@packetizer.com]
> Sent: Monday, May 29, 2000 7:46 PM
> To: Mailing list for parties associated with ITU-T Study
> Group 16; pete
> Cc: Audet, Francois [SC9:4K02:EXCH]; Alexander (Sasha) Ruditsky; Dale
> Skran
> Subject: Re: On TD26 - Fast TCS and M/S negotiation in H.323v4
>
>
> Pete, Sasha, Francois, Dale, et al,
>
> I have concerns about this document that differ from Pete's. 
> However, since
> discussion on this document has started, I thought I might as
> well express
> my concerns now while the material is fresh on people's minds.
>
> The issue has to do with the very first sentence of the
> proposal, which says
> to strike "shall not" and replace it with "may".  So, V2
> devices shall not
> send a fastStart element and an H.245 message in SETUP, but
> V4 may.  This
> seems to be a serious backward compatibility issue.  If a V2
> device were to
> receive a SETUP containing fastStart and an encapsulated
> H.245 message, what
> would it do?  I believe the behavior is not defined.
>
> Would somebody like to comment?
>
> Paul
>
> ----- Original Message -----
> From: "Pete Cordell" <pete@TECH-KNOW-WARE.COM>
> To: <ITU-SG16@mailbag.cps.intel.com>
> Sent: Saturday, May 20, 2000 1:57 PM
> Subject: On TD26 - Fast TCS and M/S negotiation in H.323v4
>
>
> > I note that TD-26 has been accepted to show how TCS can be
> conveyed in
> > parallel with fast start.
> >
> > However, the example shows the use of call proceeding for
> receiving TCS
> back
> > from the remote endpoint.  This is not typically an
> end-to-end message,
> and
> > therefore how the procedure works with the gatekeeper
> routed model needs
> to
> > be addressed.
> >
> > Possible solutions are:
> >
> > 1. Refer to the new text that says it is the responsibility of the
> > gatekeeper to forward any tunnelled message for which none
> is available
> > using FACILITY.  (There might be some objection from some to using a
> > facility message this early in the call setup process though.)
> >
> > 2. Restrict the tunnelling (and probably the fast start
> info) to Alerting,
> > Connect and Facility, which generally are end-to-end.  I
> believe this is
> > compatible with the latest procedures for deciding when
> fast start has
> been
> > ignored.
> >
> > Which ever option is chosen, it would also be nice to have
> a picture for
> it
> > also!
> >
> > Pete
> >
> > =============================================
> > Pete Cordell
> > pete@tech-know-ware.com
> > =============================================
> >
> >
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>
>