Subject: [Sip] refusing early media

From: "Brett Tate" <[email-masked]>
Date: Wed, 1 May 2002 17:13:31 -0400

What draft reflects the "accepted" working 
group solution for early media?

There were various discussions and drafts 
attempting to resolve the forking issues 
related to two devices attempting to provide 
early media.  I cannot recall or find which 
solution/message-flow was finally chosen.

Thanks in advance.

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From: Jonathan Rosenberg <[email-masked]>
Date: Wed, 01 May 2002 19:44:44 -0400

> group solution for early media?

There is no current document that explicitly addresses early media (and
is current). The consensus was that the UNIFY proposal
(draft-rosenberg-sip-unify) provided the framework we would move forward
with. In that framework, the session state is totally decoupled from the
dialog state. The offer/answer exchange affects session state, and those
exchanges could be mapped into several sip message sequences. By mapping
them into messages exchanged before the sip invite completes (inv/183)
you get early media. Aspects of this were incorporated into bis,
therefore allowing early media to be provided with bis + 100rel.
However, bis+100rel alone is not sufficient, since you will need to
modify aspects of the session before the call is answered (to handle
forking, for example). That is the reason for the UPDATE draft
(draft-ietf-sip-update) now in IETF last call. The UPDATE draft actually
has a flow that shows early media.

I do think it would be valuable to have some more early media specific
call flows, as supported by bis and update. I am not sure we need a
separate document on early media per se. Perhaps just some example call
flows in the call flows or service examples doc would be sufficient.

-Jonathan R.

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