Dear Pranab, I have not understood the call flow and it looks like that this wrong call flow for me. Please refer to RFC 3264 for offer/answer Model with the Session Description Protocol (SDP.
>>The question is - In response to the last offer by UA3, what should >>the UA2's reply ? Can it send the same SDP that it had sent in step 2 >>? >> >> My concern is, if it does so, wouldn't UA3 discard it as a duplicate SDP? RFC 3264 (section 8, Modifying the Session): The offer MAY be identical to the last SDP provided to the other party (which may have been provided in an offer or an answer), or it MAY be different. If the version in the origin line does not increment, the SDP MUST be identical to the SDP with that version number. The answerer MUST be prepared to receive an offer that contains SDP with a version that has not changed; this is effectively a no-op. However, the answerer MUST generate a valid answer (which MAY be the same as the previous SDP from the answerer, or MAY be different), according to the procedures defined in Section 6. Thanks & Best Regards, Pankaj Nath www.symphonysv.com -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Pranab Bohra Sent: Thursday, April 30, 2009 9:04 PM To: [email protected] Subject: [Sip-implementors] Question about answer with "held SDP" Hi, Following is the call flow (based on the traces taken at UA1 and UA2): 1. UA1 sends offer to UA2 (proxy) 2. UA2 forwards the offer in INVITE to another proxy UA3 3. UA3 answers to the offer with a held SDP in 200 response (because it probably does not yet know who is going to receive the call eventually) 4. UA2 ACKs the 200 response 5. UA3 sends INVITE back to UA2 immediately, this time with an updated SDP. The question is - In response to the last offer by UA3, what should the UA2's reply ? Can it send the same SDP that it had sent in step 2 ? My concern is, if it does so, wouldn't UA3 discard it as a duplicate SDP ? Thanks, Pranab _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors "This email and any files transmitted with it contain confidential, proprietary, privileged information of Symphony Services Corp (India) Pvt. Ltd. and are intended solely for the use of the recipient/s to whom it is addressed. Any unauthorized notifying, copying or distributing of this e-mail, directly or indirectly, and the contents therein in full or part is prohibited by any entity who is not a recipient. Any email received inadvertently or by mistake should be deleted by the entity who is not a recipient thereof. You may be pleased to notify the sender immediately by email and the email should be deleted from your system". _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
