Subject: [SIP] Open issues from manyfolks draft: PRECONDITION-MET and others

From: William Marshall <[email-masked]>
Date: Wed, 5 Apr 2000 09:07:45 -0400 (EDT)

At the Adelaide meeting, I believe there was general consensus on the
method described in draft-manyfolks-sip-resource-00 for qos and
security preconditions.

Two remaining issues were identified
  (1) the method needs a new name
  (2) whether the UAS can specify preconditions if the UAC doesn't

PRECONDITION-MET is clearly a bad choice of a method name.  However
with one vote each for PRE-INFO, ASSERT, CONFIRM, QUACK, PROGRESS,
ADMITTED, PRDONE, PRMET, PREMET, and PREDONE, there was clearly
no consensus among the authors.  Plenty of nominations.  Need votes.

If the UAC does not put a precondition line into the SDP, and the UAS
does, the main question is how the UAS knows that it will be honored.
(If it inserts the line and doesn't ask for a confirmation, then it 
clearly won't know if it is honored or not.  sharp stick.)

If the UAC supports reliable provisional responses, then the UAS can
ask for a PRACK, and get a PRACK with SDP with a precondition line.
UAS then knows to expect a FOOBAR message (or whatever it gets called).

If the UAC doesn't include an SDP with the PRACK, or includes an SDP
without the precondition line, then the UAS knows to not expect a FOOBAR.

So the case left open is if there is no support indicated for 100rel.
I'd consider that to mean no support for preconditions either.

Comments?

Bill Marshall
[email-masked]

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From: Henning Schulzrinne <[email-masked]>
Date: Wed, 05 Apr 2000 11:22:28 -0400

> PRECONDITION-MET is clearly a bad choice of a method name.  However

Why is that? At least it reflects what's going on...

> no consensus among the authors.  Plenty of nominations.  Need votes.

SATISFIED?

> I'd consider that to mean no support for preconditions either.

Yes, or we could use Supported to make it more explicit.

-- 
Henning Schulzrinne   http://www.cs.columbia.edu/~hgs