Hi In RFC3261, section 8.2.6.2 Headers and Tags: If a request contained a To tag in the request, the To header field in the response MUST equal that of the request. However, if the To header field in the request did not contain a tag, the URI in the To header field in the response MUST equal the URI in the To header field; additionally, the UAS MUST add a tag to the To header field in the response (with the exception of the 100 (Trying) response, in which a tag MAY be present). This serves to identify the UAS that is responding, possibly resulting in a component of a dialog ID. The same tag MUST be used for all responses to that request, both final and provisional (again excepting the 100 (Trying)). Procedures for the generation of tags are defined in Section 19.3.
I think for the dialog-creating method, like INVITE, the response with to-tag means UAS has established the dialog. And for those methods who do not create dialog, like REGISTER, the response with to-tag merely means the request is in processing. Bob ----- Original Message ----- From: "Ansari, Mohammed" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Friday, March 24, 2006 10:01 PM Subject: [Sip-implementors] To-Tag in the provisional responses to INVITE > Hi, > > According to my reading of RFC3261, it appears that sending the To-Tag > in provisional responses to an INVITE is as mandatory as in the 200OK or > final response(s). However, I have heard others mention that provisional > responses MAY not MUST contain the To-Tag. I would appreciate if some of > you can comment on this. > > Thanks. > > M. Ansari > SonyEricsson > _______________________________________________ > Sip-implementors mailing list > [email protected] > https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors > _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
