Dale Thanks for the RFC sections. As many times as I have read the spec, I have until now missed the reference to hairpinning. But your extra comments have me confused. Can you elaborate on the idea that "there can be multiple early dialogs generated by one request"? From section 8.1.1.4, the Call-ID must be the same for all messages in a dialog, but your comment implies that there can be multiple dialogs for the same Call-ID. This is where I have trouble: - What is a dialog and why would there be more than one in a call? - What is the difference between an "early dialog" and any other? - And the big kicker: if "Every dialog-starting request must have a unique Call-Id", how can there be multiple dialogs started from one request without multiple From tags?
I have been struggling with the whole dialog vs call/session concept for nearly a year, so I appreciate your explanations. Dennis > > -----Original Message----- > From: Dale R. Worley [mailto:[EMAIL PROTECTED] > Sent: Wednesday, October 26, 2005 1:59 PM > To: Sip-Implementors > Subject: [Sip-implementors] Re: [Sip] IN VITE with different from tag > ...snip... > > 8.1.1.4 Call-ID > > The Call-ID header field acts as a unique identifier to group > together a series of messages. It MUST be the same for all requests > and responses sent by either UA in a dialog. [...] > ...snip... > > Every dialog-starting request must have a unique Call-ID. It also has > to have a unique from-tag. Every successful response to the request > has to have a unique to-tag. Since there can be multiple early > dialogs generated by one request, the to-tag has to be part of the > dialog identification. In theory the from-tag could be omitted, since > it is determined by the Call-ID, but for symmetry's sake it is not. > (If the initial from-tag was omitted, an in-dialog request going in > the reverse direction would have a from-tag but not a to-tag.) > > Dale > _______________________________________________ Sip-implementors mailing list [email protected] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
