2008/9/18, Sourav Dhar Chaudhuri <[EMAIL PROTECTED]>: > Hi Rockson, > Thanks for your reply. > > By my doubt come from other scenario.like for CANCEL request RFC 3261 > specifies under said line for Via header > > Sec 9.1 > A CANCEL constructed by a client MUST have only a single Via header field > value matching the top Via value in the request being cancelled. > > > So here RFC used the word "single" before "Via header" which is not present > in the line you mentioned in Sec 8 of RFC 3261 > > And another part it is saying that "top Via value in the request being > cancelled." which it seems like request can contain multiple "Via header" > value in initial INVITE request among which top "Via header" value has to be > selected
CANCEL is hop by hop, so if a proxy receives a CANCEL (with a single Via of course) it will process it and send a CANCEL (with **just** a new Via header) to on-progress branches. But INVITE is end2end, this is, an INVITE from UAC through 4 proxies would have 5 Via headers before arriving to UAS. But if A sends a CANCEL, when the CANCEL arrives to proxy1 it generates other CANCEL containing just the same Via header P2 added to the INVITE, the same in P3 and P4. Hope it helps. -- Iñaki Baz Castillo <[EMAIL PROTECTED]> _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
