Subject: [Sip] Unify & offers in responses (Question on bis-07)

From: "Mark Watson"<[email-masked]>
Date: Tue, 19 Feb 2002 19:48:47 -0000

Jonathan,

If I understand rightly, the Unify proposal rules out SDP offers in
responses to the INVITE, except the first offer (in the case of no offer in
the INVITE).

This is on the basis that after the initial offer/answer exchange, we would
need to be able to reject such offers to deal with 'offer glare', and we
have no means of rejecting an offer in a response, right ? (NB: it is just
the SDP offer that we would need to reject, not the whole response)

Is it possible that future extensions might plug this hole, and allow
'subsequent offers' in responses ? Or, are we requiring now that any such
subsequent offers from the UAS use UPDATE ?

I am wondering whether there are requirements for a new SDP offer to be
semantically linked with a response to the INVITE, and in particular the 200
OK. e.g. your Early Media is 'sendonly' and the UAS wants to change the
stream to 'sendrecv' on Answer. Is it OK to have separate operations for the
change in dialog state and the change in media state ? or might these need
to be linked in a single operation ?

Regards...Mark

---

From: Jonathan Rosenberg <[email-masked]>
Date: Thu, 21 Feb 2002 03:38:17 -0500

Mark Watson wrote:
> responses to the INVITE, except the first offer (in the case of no offer
> in the INVITE).

Correct.

> 
> This is on the basis that after the initial offer/answer exchange, we
> would need to be able to reject such offers to deal with 'offer glare',
> and we have no means of rejecting an offer in a response, right ? (NB:
> it is just the SDP offer that we would need to reject, not the whole
> response)

Yes; there are also ordering problems, since you can't order responses
with requests in the same direction. 

> 'subsequent offers' in responses ? Or, are we requiring now that any
> such subsequent offers from the UAS use UPDATE ?

Extensions can relax constraints if there are ways to do so in a
backwards compatible manner. I believe that would be possible here, but
I don't think its needed.

> semantically linked with a response to the INVITE, and in particular the
> 200 OK. e.g. your Early Media is 'sendonly' and the UAS wants to change
> the stream to 'sendrecv' on Answer. Is it OK to have separate operations
> for the change in dialog state and the change in media state ? or might
> these need to be linked in a single operation ?

Separate is just fine! One of the big ideas of the unify draft was to
separate the evolution of dialog state from session state.

-Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.            72 Eagle Rock Avenue
Chief Scientist                         First Floor
dynamicsoft                             East Hanover, NJ 07936
[email-masked]                 FAX: (973) 952-5050
http://www.jdrosen.net                  PH:  (973) 952-5000
http://www.dynamicsoft.com

_______________________________________________
Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use [email-masked] for questions on current sip
Use [email-masked] for new developments on the application of sip