See section 9.1 of RFC 3261. You cannot send a CANCEL request until you have received a provisional response of some sort for the INVITE for the very same reasons you mention below.
Venkatesh On 1/8/07, Bob Liu <[EMAIL PROTECTED]> wrote: > > Hi > I have some question on following scenario. > 1. Alice send INVITE to Bob. > 2. Before receiving any message, Alice terminated the call. In the other > word, it send CANCEL to Bob. > 3. Because of using UDP or some other reasons, Bob receives CANCEL before > INVITE. > 4. Bob send 481 for CANCEL, and then process INVITE, 180 or 200 will be > sent. > 5. Alice receive 481, then cease retransmission of CANCEL. After that > Alice receive 180 or 200. > > Q1. Now what should be taken to inform Bob to cease the retransmission, or > just let it be? > > Q2. The other reason in 3 may be that the retransmission of INVITE cannot > ceased by sending CANCEL. So can the INVITE transaction be ceased by sending > CANCEL? > _______________________________________________ > 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
