Hi

If UAC (party A) adds a new media stream in the Re-INVITE, UAS (party B) can 
always reject it by setting port to 0. UAC should release any resources 
reserved for the new stream on getting offer rejection from the UAS.

Further, failure of Re-INVITE does not necessarily cause the call to fail. UAC 
can revert media changes to the previous state and session can continue with 
the previously negotiated media parameters.

Regards
Rohit Aggarwal
Aricent

-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Neranza Bundova
Sent: Thursday, September 18, 2008 4:48 PM
To: [email protected]
Subject: [Sip-implementors] reject sdp offer with multiple media lines

Hi All,



I am not sure how a user agent should reject an offer when:



UA "A" and UA "B" are in call and they have negotiated an audio session.

UA "A" sends re-INVITE request to "B" with SDP that rejects the media by
setting the port number to 0. UA "A" adds another media to the SDP offer
that "B" understand but can not accept.



1.      When UA "A" should release the resource used for the media
stream?

        a.      when an sdp answer from "B" is received
        b.      when "A" sends the sdp offer.

2.      What B will do in this situation?

        a.      Will send sdp answer with all media ports set to 0?
Should B close the dialog
        b.      Will send 488 response

                                                               i.
A will close the dialog

                                                             ii.      A
and B will continue the dialog and will use already negotiated media
stream

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