Hi Umesh, Since the provisional responses indicated here are reliable, the endpoints will be completing the PRACK-200 OK txns before sending failure response. one solution to this problem is when B2B is trying with CALLEE2, it can send INVITE without Offer, get CALLEE2's Offer in 180 response, forward it to CALLER as UDATE with Offer (after interworking SDP) Once B2B receives the 200 OK of UPDATE with Answer , forward it to CALLEE2 as PRACK with Answer.
So sending INVITE to CALLEE2 with or without SDP should be based on whether Answer is already forwarded to CALLER or not. rgds, Prince Umesh <[EMAIL PROTECTED]> Sent by: [EMAIL PROTECTED] 11/08/2006 11:23 AM To [email protected] cc Subject [Sip-implementors] Clarification on offer/answer Hello All, We have a B2BUA server which needs to support a particular call flow. The initial set up call flow is as shown CALLER B2BUA CALLEE1 CALLEE2 |--------INVITE(SDP1)-->| | | | |-------INVITE(SDP1)--->| | | |<--------180(SDP2)-----| | |<-------180(SDP2) -----| | | | |<---------4xx ---------| | | |----------ACK----------| | | |-------INVITE(SDP1)------------------->| | |<------180(SDP3)-----------------------| | | | The flow here is of sequential routing wherein if one user is not responding then the next number configured has to be tried until one person answers. But as you can see the issue with the flow is that the 180 with SDP3 cannot be forwarded to the caller directly. As per rules of RFC 3261,3262 as I understand when a reliable provisional response contains a session description, and is the first to do so, then that session description is the answer to the offer in the INVITE request. SDP should not be included in the subsequent 1xx-rel once offer/answer has been completed. Due to this we cannot refresh the SDP to the caller. Even use of UPDATE would result in a race condition. Please let me know if there is a solution to update the SDP( SDP3) on the caller side. Is there any other way of handling this situation? Thanks and Regards, Umesh **************************************************************************** *********** This e-mail and attachments contain confidential information from HUAWEI, which is intended only for the person or entity whose address is listed above. Any use of the information contained herein in any way (including, but not limited to, total or partial disclosure, reproduction, or dissemination) by persons other than the intended recipient's) is prohibited. If you receive this e-mail in error, please notify the sender by phone or email immediately and delete it! _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors *********************** FSS- Confidential *********************** "DISCLAIMER: This message is proprietary to Aricent 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. Aricent 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] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
