Hi, Please take a look at the draft-ietf-sipping-sip-offeranswer draft. Regards, Christer
________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Yuantao Zhang Sent: 22. toukokuuta 2008 11:55 To: [email protected] Subject: [Sip] MUST 200 OK contain SDP? Thanks Dear all I am really confused by the following part in RFC_3261. Could you please help us to explain it? Thank you very much. " 13.2.1 Creating the Initial INVITE . . . o If the initial offer is in an INVITE, the answer MUST be in a reliable non-failure message from UAS back to UAC which is correlated to that INVITE. For this specification, that is only the final 2xx response to that INVITE. That same exact answer MAY also be placed in any provisional responses sent prior to the answer. 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. . . ." Let's break it into 2 parts, in part 1, "If the initial offer is in an INVITE, the answer MUST be in a reliable non-failure message from UAS back to UAC which is correlated to that INVITE. For this specification, that is only the final 2xx response to that INVITE. " Does that mean if "Invite" contains SDP offer, "200 OK" MUST contain SDP answer. In part 2, "That same exact answer MAY also be placed in any provisional responses sent prior to the answer. 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 that mean if "Invite" contains SDP offer, the answer SDP MAY be in "180 ring" and not in "200 OK"? I think part 1 and part 2 are inconsistent. The attached sequence chart is the real problem we meet. Sx1 sends "bye" to sx2 after the "200 OK" because there is no SDP answer in "200 OK". But the producer of sx2 argues that the SDP answer is in "180 ring" already. No need to repeat it in "200 OK". Could you please tell me who is right? MUST 200 OK contain SDP? Thank you very much. Sx1 xs2 ====1 invite(SDP) ====> <====2 100 trying ==== <====3 180 ringing(SDP)==== ====4 prack ====> <====5 200 ack ====> <====6 200 OK (no SDP)====> Best Regards Yuantao Zhang
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