Hi Isshed, The new SDP must have a matching media stream for each media stream in previous SDP. Therefore, second offer from B is invalid and must be rejected by A. Please refer RFC-3264, section-8.
" If an SDP is offered, which is different from the previous SDP, the new SDP MUST have a matching media stream for each media stream in the previous SDP. In other words, if the previous SDP had N "m=" lines, the new SDP MUST have at least N "m=" lines. The i-th media stream in the previous SDP, counting from the top, matches the i-th media stream in the new SDP, counting from the top. This matching is necessary in order for the answerer to determine which stream in the new SDP corresponds to a stream in the previous SDP. Because of these requirements, the number of "m=" lines in a stream never decreases, but either stays the same or increases. Deleted media streams from a previous SDP MUST NOT be removed in a new SDP; however, attributes for these streams need not be present" Thanks, Alok Tiwari On Fri, Jan 10, 2014 at 12:11 PM, isshed <isshed....@gmail.com> wrote: > Hi All, > > Below is offer answer model between UA A and B. > > > [Offer From A] > > v=0 > o=alice 2890844526 2890844526 IN IP4 host.atlanta.example.com > s= > c=IN IP4 host.atlanta.example.com > t=0 0 > m=audio 49170 RTP/AVP 0 8 97 > a=rtpmap:0 PCMU/8000 > a=rtpmap:8 PCMA/8000 > a=rtpmap:97 iLBC/8000 > m=video 51372 RTP/AVP 31 32 > a=rtpmap:31 H261/90000 > a=rtpmap:32 MPV/90000 > > > [Answer From B] > > v=0 > o=bob 2808844564 2808844564 IN IP4 host.biloxi.example.com > s= > c=IN IP4 host.biloxi.example.com > t=0 0 > m=audio 49172 RTP/AVP 0 8 > a=rtpmap:0 PCMU/8000 > a=rtpmap:8 PCMA/8000 > m=video 0 RTP/AVP 31 > a=rtpmap:31 H261/90000 > > [Second-Offer From B] > > v=0 > o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com > s= > c=IN IP4 host.atlanta.example.com > t=0 0 > m=audio 51372 RTP/AVP 0 > a=rtpmap:0 PCMU/8000 > > [Second-Answer From A] > > v=0 > o=bob 2808844564 2808844565 IN IP4 host.biloxi.example.com > s= > c=IN IP4 host.biloxi.example.com > t=0 0 > m=audio 49172 RTP/AVP 0 > a=rtpmap:0 PCMU/8000 > m=video 0 RTP/AVP 31 > a=rtpmap:31 H261/90000 > > > Is it a valid offer answer model, as [Second-Offer From B] removes > one of the m line? > > Thanks. > _______________________________________________ > Sip-implementors mailing list > Sip-implementors@lists.cs.columbia.edu > https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors > -- Alok Tiwari | Consultant GlobalLogic P +91.120.406.2000 x 2477 M +91.991.034.7139 S alo...@globallogic.com<http://alok.t_globallogic.com/> www.globallogic.com <http://www.globallogic.com/> http://www.globallogic.com/email_disclaimer.txt _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
