That isn't entirely accurate. The branch parameter is indeed a transaction identifier, and can be used to distinguish forked REQUESTS at the UAS, but UASs don't generally need to distinguish forked requests from each other[1].
I think that Varun's real problem is distinguishing multiple RESPONSES from each other. Under these circumstances, the branch parameter is not useful, since all the responses will use the same one (by the time the response is routed back to the forking proxy). To distinguish responses, you must use the to-tag, as Paul Kyzivat has already explained. Regards Michael [1] Actually, UASs do need to detect multiple requests arriving due to forking. See RFC3261 Sec 8.2.2.2 > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:sip-implementors- > [EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] > Sent: 15 March 2007 03:45 > To: varun > Cc: [EMAIL PROTECTED]; sip- > [EMAIL PROTECTED] > Subject: Re: [Sip-implementors] Sip Registration and Invite forking > > Hi Varun, > Using Branch parameter of the Via header you can distinguish forked > branch's. The branch ID parameter in the Via header field value serves as > a transaction identifier. > > Regards > Nagendra > > > > > varun <[EMAIL PROTECTED]> > Sent by: [EMAIL PROTECTED] > 03/15/2007 08:52 AM > > > To > "Singh, Indresh \(SNL US\)" <[EMAIL PROTECTED]>, > [email protected] > cc > > Subject > Re: [Sip-implementors] Sip Registration and Invite forking > > > > > > > Hi, > Lets say Proxy srever gets an invite and it forks the > Request( since user is registered at multiple places). > I think the forked requests will have the same From,To > and call-id header fields. > So how do you distinguish them? > > > Thanks > Varun > > --- "Singh, Indresh (SNL US)" > <[EMAIL PROTECTED]> wrote: > > > > > > > -----Original Message----- > > From: [EMAIL PROTECTED] > > [mailto:[EMAIL PROTECTED] On > > Behalf Of varun > > Sent: Wednesday, March 14, 2007 2:19 PM > > To: [email protected] > > Subject: [Sip-implementors] Sip Registration and > > Invite forking > > > > Hi, > > Is contact header mandatory in SIP Registration. > > > > No > > The TO header field being the address of record is > > mapped to Contact address in Registrar when a > > registration request is received. > > In case, contact is optional then how is the mapping > > done in Registrar? > > > > > > No mapping is done in this case. A registration > > request can be received > > to fetch the existing binding information ( It is > > called query like new > > registeration, refresh, un-register, there is a > > query registration when > > a REGISTER method is received without any contact > > information ) > > > > > > Another question is about Invite forking.How are the > > forked Invite requests distinguished from each other > > or rather their responses. > > > > > > Forking requests are identified by the > > dialog-identifiers ( the from and > > to tags ). For the case where there are multiple > > bindigns associated > > with a DN and the call is forked by proxy/B2BUA, the > > call-id/session > > identifier remains same, but the dialog-ids ( > > from-tag is populated > > differently in the initial invite ). > > > > Now the responding UAS will populate different > > to-tag for each forked > > INVITE request received by them. But the proxy/B2BUA > > based on the > > call-id and tags can still figure out which session > > these responses are > > associated with and in that session which dialog > > that response is > > associated with. > > > > > > > > Thanks > > Varun > > > > > > > > > > > ________________________________________________________________________ > > ____________ > > TV dinner still cooling? > > Check out "Tonight's Picks" on Yahoo! TV. > > http://tv.yahoo.com/ > > _______________________________________________ > > Sip-implementors mailing list > > [email protected] > > > https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors > > > > > > > > > > > ________________________________________________________________________ __ > __________ > Looking for earth-friendly autos? > Browse Top Cars by "Green Rating" at Yahoo! Autos' Green Center. > http://autos.yahoo.com/green_center/ > _______________________________________________ > Sip-implementors mailing list > [email protected] > https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors > > > > *********************** Aricent- Confidential *********************** > "DISCLAIMER: This message is proprietary to Aricent and is intended solely > for the use of > the individual to whom it is addressed. It may contain privileged or > confidential information and should not be > circulated or used for any purpose other than for what it is intended. If > you have received this message in error, > please notify the originator immediately. If you are not the intended > recipient, you are notified that you are strictly > prohibited from using, copying, altering, or disclosing the contents of > this message. 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