[rtcweb] SDP_PRANSWER followed by SDP_OFFER scenario in JSEP

"Ravindran, Parthasarathi" <pravindran@sonusnet.com> Mon, 30 April 2012 07:01 UTC

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From: "Ravindran, Parthasarathi" <pravindran@sonusnet.com>
To: Justin Uberti <juberti@google.com>, Cullen Jennings <fluffy@iii.ca>
Thread-Topic: SDP_PRANSWER followed by SDP_OFFER scenario in JSEP
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Date: Mon, 30 Apr 2012 07:01:38 +0000
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Cc: "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: [rtcweb] SDP_PRANSWER followed by SDP_OFFER scenario in JSEP
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Could you please explain in case for an SDP_OFFER(1), the remote entity replies with SDP_PRANSWER followed by new SDP_OFFER (2) what is the expected behavior. The exact callflow is as follows:

Browser1-------------------------Browser2(SIP-JSEP gateway)
    |        SDP_OFFER(1)            |  INV with offer1
    |       SDP_PRANSWER(1)          |  183 with answer1
    |       SDP_OFFER(2)             |   UPDATE with offer2
    |       SDP_ANSWER(2?)           |

The reason for this O/A callflow is due to UPDATE method (RFC 3311) mapping in Browser 2 (SIP-JSEP gateway). 


PS: For simplicity, PRACK message exchange is not chosen in SIP side.