A BYE will terminate a specific dialog. A CANCEL is intended to cancel all branches (all early dialogs) of a potentially forked INVITE. If an INVITE was forked by a forking proxy, the CANCEL is sent on all branches of the fork. Sending BYE on an early dialog can be used to cancel/terminate a single branch and let the INVITE complete on the remaining branches.
Also, if the CANCEL does not reach a given UAS before it answers (sends a 2xx response), the session will continue. If a BYE is sent on an early dialog, it will be terminated whether or not the BYE arrives before a 2xx response is sent. cheers, (-:bob -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Romel Khan Sent: Monday, July 25, 2011 2:01 PM To: [email protected] Subject: [Sip-implementors] BYE before call answer RFC3261, sec 15 : "Typically, when the user hangs up, it indicates a desire to terminate the attempt to establish a session, and to terminate any sessions already created. For the caller's UA, this would imply a CANCEL request if the initial INVITE has not generated a final response, and a BYE to all confirmed dialogs after a final response.". So in this text, it is implying CANCEL is to be sent to terminate a session & dialog before call answered. But an earlier paragraph in same section sec 15:: "The caller's UA MAY send a BYE for either confirmed or early dialogs". Why has the RFC left open the option to send BYE before call has answered? If CANCEL is meant to be the METHOD to send before INVITE in accepted to terminate the session & dialog, why also allow BYE? Or to ask the other way, why create & define the CANCEL method if BYE can be used to terminate the session & dialog before call answered? _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
