Comments inline > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED]]On Behalf Of Arun Patra > Sent: 14 December 2001 11:44 > To: 'Jonathan Rosenberg' > Cc: [EMAIL PROTECTED] > Subject: [Sip-implementors] Multiple dialogs in Forking Scenario > > > Hi, > I have following question.Just look into following lines which are from > 2543bis.05 > > ----page-45, section 13.1, last paragraph--- > A 2xx response to an INVITE establishes a session, and it also creates a > dialog between the UA that issued the INVITE and the UA that generated the > 2xx response. Therefore, when > multiple 2xx responses are > received from different remote UAs (because the INVITE forked), each 2xx > establishes a > different dialog. > All these dialogs are part of the same call. > ----------------------- > > In above why different dialogs for forking case. After proxy fork > a request > received from a UAC, the first 2xx response it got from any of > those forked > endpoints is the valid one. Other 2xx responses received later than first > 2xx assumed to be in-valid
Hi Arun, Other 2xx responses are not invalid. If a second phone is ringing and somebody answers at that second phone, then it's perfectly legitimate for a 200 to be sent. The second phone can't know that the first phone has already answered. > and proxy sends a CANCEL to each > forked endpoint > other than the first one. The 200 from the second phone could be sent before the second receives the CANCEL from the proxy. The messages could pass eachother on the wire. > If proxy is call-statefull all the > dialogs created > for that call are maintained in proxy level. > So multiple 2xx will never reach to originator UAC. The discussion of stateful proxies in bis-05 is concerned with transaction-stateful proxies. Multiple 2xx can reach the UAC. This is explained in a few parts of bis-05, but it's stated quite clearly that this can happen in section 16.6 for example: After a final response has been sent on the server transaction, the following responses MUST be for- 2342 warded immediately: 2343 Any 2xx class response to an INVITE request 2344 A stateful proxy MUST NOT immediately forward any other responses. 2345 > Then why different > dialogs for same call at UAC in a forking scenario? A dialog is "a peer-to-peer SIP relationship between a UAC and UAS that persists for some time." If a 2xx repsonse is received by a UAC from a second UAS, then it has a signalling relationship with that second UAS. Bye, Brian > Ofcourse if UAC forked the request, then it has to. But should UAC fork a > message? > > p.s. Apologies if this topic already discussed. > > regards > Arun > _______________________________________________ > 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
