Subject: Re: [Sip] mayfolks

From: William Marshall <[email-masked]>
Date: Fri, 15 Mar 2002 09:08:40 -0500 (EST)

Salva wrote:
> 	is it allowed to send an answer with preconditions to an offer 
> that didn't contain them (not even the none option tag)?

This is the case that led to my suggestion that a MUST be added
to the last paragraph of section 5.1.  If the offerer MUST generate
the SDP by the rules of 5.1.1 and section 4, then there will be a
precondition line containing "none" and the answer can upgrade it.

Otherwise, when the offer is made by the UAS, there is no mechanism
for the UAC to know whether preconditions were supported or not.
(When the offer is made by the UAC, then the Supported header can
indicate this, but this doesn't work the other direction).

Bill Marshall
[email-masked]

-----original message-----
From: "Salva Rey Calatayud" <[email-masked]>
To: [email-masked]
Date: Fri, 15 Mar 2002 14:17:08 +0100
Subject: [Sip] mayfolks

Hi,

	is it allowed to send an answer with preconditions to an offer 
that didn't contain them (not even the none option tag)?

thanks
Salva

**********************************
Salvador Rey Calatayud,  M.Sc.
Siemens AG                       Room 53521
[email-masked]           Munich, Perlach 
Phone number : +49-16095178051
**********************************

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---

From: Gonzalo Camarillo <[email-masked]>
Date: Fri, 15 Mar 2002 19:59:02 +0200

Hi

> indicate this, but this doesn't work the other direction).

Exactly. Besides, the supported header does not tell anything about the
preconditions types (e.g., qos) supported. Lines with none tags do.

Regards,

Gonzalo

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---

From: Jonathan Rosenberg <[email-masked]>
Date: Sun, 17 Mar 2002 20:22:01 -0500

> preconditions types (e.g., qos) supported. Lines with none tags do.

Whilst I don't disagree that its better to insert preconditions only in
the answer if the none precondition was present in the offer, I actually
do think Supported ought to be allowed in the 1xx. This is not the case
according to table 2, unfortunately, which makes no mention of its
presence in anything but 2xx. However, I would think that it is sensible
in any response that establishes a dialog, which includes, but is not
limited to, 2xx. The same goes for other headers like Accept,
Accept-Encoding, Allow, etc.

-Jonathan R.

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