On Tue, 2002-03-05 at 08:57, Luo, Helen wrote: > Hi, > > I just start to dig into SIP. When I read RFC 2543, couldn't find anywhere > mention about retransmission SIP response, mainly 4xx, 5xx and 6xx. > > The following is one of the case I confused: > > If something goes wrong before final 200 response received, CANCEL > will be sent to the UAS. > > UAC UAS > | | > | | > ---------CANCEL--------------> > | | > |<--------200 -------------------| > | | > |<--------487 call cancelled| > | | > |----------ACK ---------------->| > > > 1) Do we need retransmission 487? The state machine for the INVITE transaction is not affected by the CANCEL transaction (the TU on top of that state machine will get affected, assuming it hasn't already sent a final response to the INVITE).
So, over a non-reliable hop (UDP), the 487 will be retransmitted if the ACK doesn't arrive in time. > 2) Is there timers after send out 487 to wait ACK? The same timers that you would have run if you returned a 404 (or any other non-2xx final response). > 3) Is it possible 487 is received before 200? Sure. The INVITE and CANCEL transactions complete independently. > > Thanks in advanced, > > Helen Luo > 972-461-6330 > > > _______________________________________________ > Sip-implementors mailing list > [EMAIL PROTECTED] > http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors _______________________________________________ Sip-implementors mailing list [EMAIL PROTECTED] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
