Hi Paul, Let me modify Thangarajan flow a bit so that the flow is valid from both ends.
Alice Bob 1) | Invite (SDP offer )------> | 2) | <------- 183 (SDP answer)- | 3) | Prack (for 183)----------> | 4) | <------- 200 Ok for Prack- | 5) | <------- 180 ------------- | 6) | --Prack (SDP offer)------> | //Messages 6 & 7 cross on wire 7) | <--- 200 Invite(SDP offer) | //Messages 6 & 7 cross on wire Suppose that messages 6 & 7 cross on wire. One offer/answer exchange has already happened (1&2). So at 6 Alice can send an offer in Prack. Also, before this Prack reaches Bob, he can send a 200 OK, with offer, for INVITE (Note: he did not send an SDP in 180). What should be the behavior at both ends in this case? Thanks and regards, Vibhuti -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: Saturday, December 03, 2005 9:54 AM To: Paul Kyzivat Cc: [EMAIL PROTECTED]; Kavita Rai; Seshu; '[email protected]'; [EMAIL PROTECTED]; Vibhuti V Natraj Subject: Re: [Sip-implementors] Prack Offer/answer scenario Hi Paul, Invite (SDP offer )------> <------- 180 (no SDP) <------- 200 Ok for Invite (SDP answer) Prack (SDP)------> In the above case PRACK should not have SDP(offer). But if UAC misbehave, by sending SDP in the PRACK request. Then what UAS should do. What error code(4xx) is appropriate here. UAS can not discard this PRACK message because "If the UAS does send a final response when reliable responses are still unacknowledged, it SHOULD NOT continue to retransmit the unacknowledged reliable provisional responses, but it MUST be prepared to process PRACK requests for those outstanding responses. " Regards, Thangarajan. Paul Kyzivat <[EMAIL PROTECTED] om> To Sent by: [EMAIL PROTECTED] sip-implementors- are.com [EMAIL PROTECTED] cc ia.edu Seshu <[EMAIL PROTECTED]>, Vibhuti V Natraj <[EMAIL PROTECTED]>, 12/02/2005 07:22 "'[email protected]' PM " <[email protected]>, Kavita Rai <[EMAIL PROTECTED]> Subject Re: [Sip-implementors] Prack Offer/answer scenario [EMAIL PROTECTED] wrote: > > > > Hi kavitha, > > I have few doubts about the call flow given > > Rfc 3262 says "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 ". > In this call flow the answer must be generated either in 18x or 2xx but in > call flow given neither 18x or 2xx contain the Answer. > > Even though lets assume that you generated the answer in 2xx (final > response), I am not sure whether RFC mentions the UAC handling > for pending PRACK with SDP ?? In case PRACK without SDP is received then > 2xx for PRACK may be the proper response. > > Waiting for the reply from sip gurus......... I agree the flow below is wrong. More below. Paul > Rgds, > Gururaj. > > > > > > Kavita Rai > <[EMAIL PROTECTED] > ch.com> To > Sent by: "'[email protected]' > sip-implementors- " > [EMAIL PROTECTED] <[email protected]> > ia.edu cc > Seshu <[EMAIL PROTECTED]>, > Vibhuti V Natraj > 12/01/2005 11:40 <[EMAIL PROTECTED]> > AM Subject > [Sip-implementors] Prack > Offer/answer scenario > > > > > > > > > > > Hi, > Section 3 of RFC 3262 mentions > > "The UAS MAY send a final response to the initial request before having > > received PRACKs for all unacknowledged reliable provisional responses, > > unless the final response is 2xx and any of the unacknowledged reliable > > provisional responses contained a session description." > > In a scenario the reliable 1xx did not have SDP and we go ahead and > > send 2xx for Invite without waiting for Prack. What if the Prack for the > relaible 1xx we receive has an offer? > > Invite (SDP)------> The above SDP is the offer > <------- 180 (no SDP) > > <------- 200 Ok for Invite (No SDP) The above violates 3261. The 200 MUST contain an answer. > Prack (SDP)------> And this violates both 3262 and 3264 - it is sending another offer in a prack when there has been no answer to the earlier offer. > <------ 200 OK(SDP) > > By sending the offer in PRACK user wanted to re-negotiate the parameters, > but in this case we have already sent 2xx for invite and other side will > respond with ACK and the session will be established as per SDP exchange in > Invite and 1xx. > > How does above statement mentioned above from the RFC take care of this > scenario?? > > Will be grateful to have some direction from you on this.. > > Regards, > > Kavita Rai > E-mail: <mailto:[EMAIL PROTECTED]> [EMAIL PROTECTED] > > This message (including any attachments) is a confidential and Privileged > communication to the intended addressee. If you are not the Intended > addressee, you have received this message in error. In that case, please > permanently delete this message and notify the sender so that we can avoid > this inconvenience in the future. Thank you. > > > _______________________________________________ > Sip-implementors mailing list > [email protected] > http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors > > > > *********************** FSS-Unclassified *********************** > "DISCLAIMER: This message is proprietary to Hughes Software Systems Limited > (HSS) and is intended solely for the use of the individual to whom it is > addressed. It may contain privileged or confidential information and > should not be circulated or used for any purpose other than for what it is > intended. If you have received this message in error, please notify the > originator immediately. If you are not the intended recipient, you are > notified that you are strictly prohibited from using, copying, altering, or > disclosing the contents of this message. HSS accepts no responsibility for > loss or damage arising from the use of the information transmitted by this > email including damage from virus." > > _______________________________________________ > Sip-implementors mailing list > [email protected] > http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors > _______________________________________________ Sip-implementors mailing list [email protected] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors *********************** FSS-Private *********************** "DISCLAIMER: This message is proprietary to Hughes Software Systems Limited (HSS) and is intended solely for the use of the individual to whom it is addressed. It may contain privileged or confidential information and should not be circulated or used for any purpose other than for what it is intended. If you have received this message in error, please notify the originator immediately. If you are not the intended recipient, you are notified that you are strictly prohibited from using, copying, altering, or disclosing the contents of this message. HSS accepts no responsibility for loss or damage arising from the use of the information transmitted by this email including damage from virus." _______________________________________________ Sip-implementors mailing list [email protected] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
