On Tue, 2008-12-09 at 10:04 +0000, Michael Procter wrote: > > The to-tag we needed to identify forked responders generating > unique early-dialogs with a common Call-ID, but why did we need the > UAC to generate a from-tag? (I'm feeling dumb that I can't figure out > the answer) > > > > In the reverse direction, the presence of a to-tag in a request > indicates an in-dialog request. Therefore, requiring a from-tag ensures > that requests in the reverse direction can have a to-tag, and thus be > correctly treated as in-dialog.
I'm looking at the code in sipX that works with tags to determine the status of a SIP message, and though the from-tag is not logically necessary, it does make the code simpler, as the To and From URIs are handled more symmetrically. In addition, it allows the SIP element to extract and compare only the tags, rather than having to compare the To/From URIs (as is required in RFC 2543), which is always fraught with problems. Dale _______________________________________________ Sip mailing list https://www.ietf.org/mailman/listinfo/sip This list is for NEW development of the core SIP Protocol Use [email protected] for questions on current sip Use [email protected] for new developments on the application of sip
