Hi Anjan, In this case, call is just initiated by sending INVITE request from UAC but since nothing has been received from UAS, so as per UAC behaviour from RFC 3261, UAC cannot send CANCEL for this request. Because it may be the case that INVITE has not even reached to UAS and ignored in between only.
RFC 3261 says about this: " Once the CANCEL is constructed, the client SHOULD check whether it has received any response (provisional or final) for the request being cancelled (herein referred to as the "original request"). If no provisional response has been received, the CANCEL request MUST NOT be sent; rather, the client MUST wait for the arrival of a provisional response before sending the request." Regards, Kamini -----Original Message----- From: sip-implementors-boun...@lists.cs.columbia.edu [mailto:sip-implementors-boun...@lists.cs.columbia.edu] On Behalf Of Anjan Naik Sent: 31 December 2014 12:04 To: sip-implementors@lists.cs.columbia.edu Subject: [Sip-implementors] Cancelling a call before Provisional response HI All, I have a query regarding Cancelling a call before Provisional response. As per RFC 3261, CANCEL can be sent after a provisional response (1xx response other than 100) receivecd. Suppose i make a call steps: 1) INIVITE sent to Callee 2) Callee didn't send anything Now i want to cancell the call. What shold be call flow ? Thanks, Anjan _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors "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 Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors