Jo There is text in the bis draft (10.46.6 of bis-04) about the computation of a branch that would indicate that it is built as a unique value for each proxy. >From this, it appears reasonable to conclude that the branch parameter in the VIA uniquely identifies the proxy the request came from. It would be reassuring, of course, to have this explicitly stated in the specification. Regards, Venkat
-----Original Message----- From: Jo Hornsby [mailto:[EMAIL PROTECTED]] Sent: Friday, October 26, 2001 4:02 AM To: Arunachalam Venkatraman; Jonathan Rosenberg; [EMAIL PROTECTED] Subject: RE: [Sip-implementors] RE: [Sip] Isomorphic Request Definition > Is it acceptable for a UA to merely use the presence of a branch > parameter in the VIA to distinguish a request as having been > received from a proxy instead of from another UA. I would see this as bogus. I can see no reason why a UA might not logically combine the roles of UAC and proxy, and fork, for instance; in which case it would have to weave branch magic. > I am also interested in determining whether all parameters in a > VIA need to be used or just the branch alone will do to > distinguish one proxy from another, in the case of a merged > request at the UA. I would consider it unlikely that you would get branch collisions from different proxies; however, I am struggling to find anything in bis-05 &:) that actually mandates this. In any case, for robustness, it would seem wise to always inspect the topmost Via's "sent-by" when involved in such procedures. (I might note that this would seem to be a slight augmentation of step 2 of Section 13.3.1.) > Finally, is the branch a mandatory parameter when a proxy adds > a VIA to the request? Neither the rfc nor the bis-04 specify > this explicitly. But they seem to strongly imply this. For > example, bis04 states in 10.46.6 Syntax > [The "branch" parameter is included by every proxy.] The branch parameter is mandatory. See step 3 of Section 16.5. (It was also mandatory as viewed by bis-04; see section 17.3.1.) - Jo. _______________________________________________ Sip-implementors mailing list [EMAIL PROTECTED] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
