Hi Paul, If A has 2 contact address 1.1.1.1 and 1.1.1.2 for the same AOR. Now if A and B are in session using 1.1.1.1. And if A wants to change it to 1.1.1.2. Can A use Re Invite as a target refresh request with contact 1.1.1.2? If yes, how UA with Ip 1.1.1.2 will know about the existing call.
Thanks Vivek On Tue, 22 Jun 2004 Paul Kyzivat wrote : > > >SiM wrote: >>Hi All, >> Under what scenarios are a Target Refresh Request issued, to change the >> remote target URI of a Dialog, using a Re-INVITE ? >> some examples would be appreciated. > >Most of the applications of this that I know of are pretty obscure, related to fault >tolerance schemes. The most common case that comes to mind is in the transition of a >2-party call into conference with a conference focus. In simple cases the original >node will remain as the focus, but the contact is supposed to change to indicate that >it is a focus. It might look something like: > > A B C > | | | > | 1) INVITE | | > |------------>| | > | 2) 200 | | > |<------------| | > | 3) ACK | | > |------------>| 4) INVITE/Join | > | |<---------------| > | | 5) 200 | > | 6) INVITE |--------------->| > |<------------| | > | 7) 200 | | > |------------>| 8) ACK | > | 9) ACK |<---------------| > |<------------| | > >2) 200 OK > To: B > From: A > Contact: sip: [EMAIL PROTECTED] > >5) 200 OK > To: B > From: C > Contact: sip:[EMAIL PROTECTED];isFocus > >6) INVITE > To: A > From: B > Contact: sip:[EMAIL PROTECTED];isFocus > >Here, when B receives the request from C to join into the call with A, it sets up a >contact denoting the conference to be, and uses that for the new dialog with C. Then >it does a reINVITE with A to accomplish the target refresh request, letting it know >it is now in a conference. > >Its clearer when the contact address actually changes, as above, but the same thing >can be accomplished without, as in: > >2) 200 OK > To: B > From: A > Contact: sip: [EMAIL PROTECTED] > >5) 200 OK > To: B > From: C > Contact: sip:[EMAIL PROTECTED];isFocus > >6) INVITE > To: A > From: B > Contact: sip:[EMAIL PROTECTED];isFocus > >Here the target refresh doesn't change the contact address itself, but does add >contact header parameters. > >Paul > >_______________________________________________ >Sip-implementors mailing list >[EMAIL PROTECTED] >http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
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