Hi, I agree with Christer. Additional comments inline.
> > Hi, > > Some comments inline ([CHH]) > > >>2. RFC 3261 says in 13.2.1 that :- > >> "The UAC MUST treat the first session description > >>it receives as the answer, and MUST ignore any session descriptions in subsequent > >>responses to the initial INVITE." > >> > >> - Does this mean that if an INVITE is sent with SDP > >>(offer) and then if it receives a non reliable provisional response > >>with SDP and then it gets a 200 OK with SDP, then only the SDP in non-reliable > >>provisional response must be considered as answer and the SDP in 200 OK > >>must be blindly ignored ? > > In my understaning, this means also that the SDP in non-reliable provisional responses following the first non-reliable provisional response with SDP must be blindly ignored. So the SDP in the second 183 response in your scenario will be ignored. If you want change the session parameters from the callee before INVITE transaction completes, the callee can use UPDATE method if "UPDATE" is included in Allow header in the INVITE request it received. Regards, Takuya > >Yes. > > [CHH] As was said earlier, non reliable provisional responses may get lost, so from > that perspective you should be able to use also the SDP in the 200 OK (which, if the remote node behaves correctly, shall be the same as in the non reliable provisional response). > > >>3. Is the following scenario possible :- > >> > >> A B > >> | | > >> | INVITE (SDP OFFER) | > >> |--------------------->| > >> | | > >> | | > >> | 183 (SPD ANSWER) | > >> |<---------------------| > >> | PRACK (NO SDP ) | > >> |--------------------->| > >> | PRACK 200 OK(NO SDP) | > >> |<---------------------| > >> | | > >> | | > >> | | > >> | 183 (SDP OFFER) | > >> |<---------------------| > >> | PRACK ( SDP ANSWER) | > >> |--------------------->| > >> | PRACK 200 OK(NO SDP) | > >> |<---------------------| > >> | | > >> | | > >> | | > >> | 200 OK(NO SDP) | > >> |<---------------------| > >> | ACK (NO SDP ) | > >> |--------------------->| > >> | | > >>In the above diagram, I specifically wanted to know whether > >>calle party (B) can send an OFFER SDP in the second reliable > >>provisional response ? > >I believe this is OK. > > [CHH] My understanding is that only the first reliable provisoinal response may > contain an offer, and only in the case that the initial INVITE didn't contain one (in which the answer is sent in the first PRACK). > > I think that there can only be one offer/answer exchange per transaction, so once a > SDP (offer or answer) has been sent in a provisional response no more can be sent for that transaction (INVITE). Or? > > IF we were allowed to send more offers in provisional responses, how would we handle > race conditions if the UAC at the same time sends a new offer (we can't send 491 to a provisional response)? > > Regards, > > Christer Holmberg > Ericsson Finland > > _______________________________________________ > Sip-implementors mailing list > [EMAIL PROTECTED] > http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors -------- Takuya Sawada KDDI Corporation (KDDI) Garden Air Tower, 3-10-10 Iidabashi Chiyoda-ku Tokyo 102-8460, Japan Tel: +81-3-6678-2997 Fax: +81-3-6678-0285 [EMAIL PROTECTED] _______________________________________________ Sip-implementors mailing list [EMAIL PROTECTED] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
