Subject: RE: [SIP] comments on draft-ietf-sip-100rel-01.txt

From: "Schroeder, Tim" <[email-masked]>
Date: Fri, 2 Jun 2000 14:14:34 -0500

> > Section 5.1, Paragraph 11: "It is not necessary to include the Supported
> > header listing the option tag 100rel in the PRACK request."

> Given the change that you can't send a reliable provisional response to
> PRACK, it seems this text is actually fine - its not needed to include
> this Supported header in PRACK.

Given the change that you can't send a reliable provisional response to
PRACK, perhaps the current text could remain, and an additional sentence
prohibiting the use of "Require: 100rel" in a PRACK request should be added.
Otherwise, somewhere we'd probably have to clarify what to do if a UAC
requires reliable provisional responses, but the UAS is prohibited from
sending them reliably.  

I'm still in the "no reliable provisional responses to a PRACK" camp.  If
they were allowed, then presumably the UAC would have the right to require
them (unlike the proposed change above).  This seems like it could lead to
trouble in an environment where the UAC and UAS are implemented by different
parties, who don't necessarily trust each other.  Suppose a UAC requires all
provisional responses to be sent reliably for all requests, and habitually
includes "Require: 100rel" in its messages.  That doesn't seem to be too
much of a stretch, or to unequivocally imply a badly written UAC.  And
suppose a UAS desires to send a provisional response to a PRACK (I can't
think of an obvious example here, but if *reliable* provisional responses
are useful, certainly provisional responses must be useful to begin with!).
This would lead to the never-ending series of PRACKs arriving at the UAS,
and the UAS would have to decide not to send provisional responses at all to
defend itself; if it sent a response, it'd be required to do so reliably,
and that would result in yet another PRACK. 

Tim Schroeder
[email-masked]
SBC Technology Resources, 9505 Arboretum Blvd., Austin, TX  78759

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From: Jonathan Rosenberg <[email-masked]>
Date: Sun, 04 Jun 2000 23:17:04 -0400

> requires reliable provisional responses, but the UAS is prohibited from

I added this wording.

> 
> I'm still in the "no reliable provisional responses to a PRACK" camp.

Well, since there were two folks speaking against it, and I spoke for it
but was on the fence, consensus seemed to be to remove it, so its gone -
issue resolved.

-Jonathan R.
-- 
Jonathan D. Rosenberg                       72 Eagle Rock Ave.
Chief Scientist                             First Floor
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