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 ? > >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
