Assume Dialog identifier is : 1. Only call id : Scenarios where call made to itself like self-testing .here Call-Id is same but we would need tags to identify caller and callee dialog. 2. CallId and from-tag : Forking scenarios where callId is same for all early dialogs(A-B1,A-B2) and from-tag also same so wont able to distinguish early dialogs without using to-tags .
Hence thinking of all possible scenarios ,we would realise that we need combination of call-id,from tag and to tag to identify unique dialog even if callid is anyway generated unique across call. Regards Ankur Bansal On Tue, Oct 27, 2015 at 6:29 PM, Anand Konji <abko...@gmail.com> wrote: > Just adding more info to Brett's ans, > > Callid and from tag are added by source. > To rag is added by destination. > So dialog will be formed by contribution of both end. This would have not > possible if rfc documented as you said. > On Oct 27, 2015 6:03 PM, "Brett Tate" <br...@broadsoft.com> wrote: > > > The Call-ID is obvious. The To tag helps handle forking situations. > > > > The From tag used to be optional during call setup. It became mandatory > > because a common issue was that devices and operators occasionally > > incorrectly classified re-INVITE as INVITE because the To tag was missing > > to help with the analysis. > > > > > > > -----Original Message----- > > > From: sip-implementors-boun...@lists.cs.columbia.edu [mailto:sip- > > > implementors-boun...@lists.cs.columbia.edu] On Behalf Of Harshith > Mulky > > > Sent: Tuesday, October 27, 2015 8:20 AM > > > To: sip-implementors@lists.cs.columbia.edu > > > Subject: [Sip-implementors] Need of From/To Tag in SIP Dialog > > > > > > We all know a SIP dialog is complete when it comprises of Call-ID, From > > Tag > > > and the To Tag. > > > > > > Why do we have 3 different things to complete a Dialog when we could > > only > > > have Call-ID to complete a Dialog > > > > > > _______________________________________________ > > > Sip-implementors mailing list > > > Sip-implementors@lists.cs.columbia.edu > > > https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors > > _______________________________________________ > > Sip-implementors mailing list > > Sip-implementors@lists.cs.columbia.edu > > https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors > > > _______________________________________________ > Sip-implementors mailing list > Sip-implementors@lists.cs.columbia.edu > https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors > _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
