Re: [rtcweb] SDP_PRANSWER followed by SDP_OFFER scenario in JSEP

Hi Charles,

UPDATE is allowed in the early dialog and I haven't shown in the callflow for simplicity as I mentioned in PS of below mail as " PS: For simplicity, PRACK message exchange is not chosen in SIP side."

Thanks
Partha

>-----Original Message-----
>From: Charles Eckel (eckelcu) [mailto:eckelcu@cisco.com]
>Sent: Monday, April 30, 2012 9:53 PM
>To: Ravindran, Parthasarathi; Justin Uberti; Cullen Jennings
>Cc: rtcweb@ietf.org
>Subject: RE: [rtcweb] SDP_PRANSWER followed by SDP_OFFER scenario in
>JSEP
>
>Hi Partha,
>
>I believe such a flow illegal, per RFC 3311:
>
>      o  If the UPDATE is being sent before the completion of the INVITE
>         transaction, and the initial INVITE contained an offer, the
>         UPDATE cannot be sent with an offer unless the callee has
>         generated an answer in a reliable provisional response, has
>         received a PRACK for that reliable provisional response, has
>         not received any requests (PRACK or UPDATE) with offers that it
>         has not answered, and has not sent any UPDATE requests
>         containing offers that have not been answered.
>
>Cheers,
>Charles
>
>> -----Original Message-----
>> From: rtcweb-bounces@ietf.org [mailto:rtcweb-bounces@ietf.org] On
>> Behalf Of Ravindran, Parthasarathi
>> Sent: Monday, April 30, 2012 12:02 AM
>> To: Justin Uberti; Cullen Jennings
>> Cc: rtcweb@ietf.org
>> Subject: [rtcweb] SDP_PRANSWER followed by SDP_OFFER scenario in JSEP
>>
>> Justin/Cullen,
>>
>> 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).
>>
>> Thanks
>> Partha
>>
>> PS: For simplicity, PRACK message exchange is not chosen in SIP side.
>>
>>
>>
>>
>>
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