Hi Vivek, As per RFC 3261 Section 9.1, To tag is compulsary for all the requests. See the snippet below ....
The following procedures are used to construct a CANCEL request. The Request-URI, Call-ID, To, the numeric part of CSeq, and From header fields in the CANCEL request MUST be identical to those in the request being cancelled, including tags. .... Now as per your question, If UAS is sending 481, it means it does not have any matching transaction i.e. it has not received INVITE or the headers in CANCEL do not match with that of any present INVITE transactions in server. Solution: For the first part, UAC must ensure not to send CANCEL before receiving provisional response from UAS. For the second part, UAC must ensure the header values to be same as described in above snippet. Thanks and Regards Gaurav Khare ----- Original Message ----- From: "Vivek Batra" <[email protected]> To: <[email protected]> Sent: Tuesday, January 22, 2013 9:37 AM Subject: [Sip-implementors] Canceling INVITE Transaction... > Hi folks, > > > > I am facing issue with one specific service provider where caller wants to > cancel the transaction and sends CANCEL message but UAS responds with 481 > Call Leg/Transaction Does Not Exist. I assume that as per RFC 3261, CANCEL > message should not contain the To tag however in the below message, I can > see To tag coming in CANCEL message from service provider. > > Do you think UAS should ignore the To tag and complete the CANCEL > transaction? > > > > Best Regards, > > Vivek Batra > > > > Request-Line: INVITE sip:[email protected]:5060 SIP/2.0 > > From: > sip:[email protected]:5060;user=phone;tag=ccid-615150755-355499422 > > Via: SIP/2.0/UDP 69.132.136.5:5060;branch=z9hG4bK-355499422-1 > > To: sip:[email protected]:5060 > > Call-ID: [email protected] > > CSeq: 1 INVITE > > > > Status-Line: SIP/2.0 180 Ringing > > From: > <sip:[email protected]:5060>;tag=ccid-615150755-355499422;user=phone > > To: > <sip:[email protected]:5060>;tag=5ffef8-8801a8c0-13c4-50efa087-15a2 > dc08-50efa087 > > Call-ID: [email protected] > > CSeq: 1 INVITE > > Via: SIP/2.0/UDP > 69.132.136.5:5060;received=69.132.196.11;branch=z9hG4bK-355499422-1 > > Contact: <sip:[email protected]:5060;transport=udp> > > > > Request-Line: CANCEL sip:[email protected]:5060 SIP/2.0 > > Via: SIP/2.0/UDP 69.132.196.11:5060;branch=z9hG4bK-355499422-1 > > From: > sip:[email protected]:5060;user=phone;tag=ccid-615150755-355499422 > > To: > <sip:[email protected]:5060>;tag=5ffef8-8801a8c0-13c4-50efa087-15a2 > dc08-50efa087 > > Call-ID: [email protected] > > CSeq: 1 CANCEL > > Contact: sip:69.132.196.11:5060 > > > > Status-Line: SIP/2.0 481 Call Leg/Transaction Does Not Exist > > From: > <sip:[email protected]:5060>;tag=ccid-615150755-355499422;user=phone > > To: > <sip:[email protected]:5060>;tag=5ffef8-8801a8c0-13c4-50efa087-15a2 > dc08-50efa087 > > Call-ID: [email protected] > > CSeq: 1 CANCEL > > Via: SIP/2.0/UDP 69.132.196.11:5060;branch=z9hG4bK-355499422-1 > > > > > > Best Regards, > > Vivek Batra > > > > > > _______________________________________________ > Sip-implementors mailing list > [email protected] > https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors > ________________________________ DISCLAIMER: The information in this message is confidential and may be legally privileged. It is intended solely for the addressee. Access to this message by anyone else is unauthorized. If you are not the intended recipient, any disclosure, copying, or distribution of the message, or any action or omission taken by you in reliance on it, is prohibited and may be unlawful. Please immediately contact the sender if you have received this message in error. Further, this e-mail may contain viruses and all reasonable precaution to minimize the risk arising there from is taken by OnMobile. OnMobile is not liable for any damage sustained by you as a result of any virus in this e-mail. All applicable virus checks should be carried out by you before opening this e-mail or any attachment thereto. Thank you - OnMobile Global Limited. _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
