Ramachandran Iyer wrote:
>
> hi,
>
> as we know that
>
> Via is always used to forward responses.
> Route is always used to determine where to forward
> requests
>
> Also let us consider a typical call flow..assume two
> intermediate proxies..( A-->p1-->p2-->B)
>
> INVITE -- RecordRoute: p2,p1
> 200 (invite) -- RecordRoute: p2,p1
> ACK -- Route : p2,b
> BYE -- Route : p1,b
> 200 (bye)
> ---------------------------------------------
>
> Now my query is what is the need for the Via: list
> being built up for ACK as it traverses from
> (A-->p1-->p2-->B)as Via: is used by responses to trace
> back the path, but ACK does not generate any
> responses.
[...]
> In a Nut-shell is it fair to say that the Route for
> subsequent transaction is known to both client and
> server upon the receiving of a 200 from B-->A. (when B
> relays it through the record-route).
Yes; the UAS can build the route set on receiving the INVITE (and generating
a 200 OK, of course), and the UAC can build the route set on receiving the
200 OK. Once the route set has been built, subsequent requests, including
ACK, will follow it.
Even though ACK does not generate a response, any intermediate SIP entities
processing it have to follow the rules of processing requests, including
inserting a Via.
Regards,
- vijay
--
Vijay K. Gurbani vkg@{lucent.com,research.bell-labs.com,acm.org}
Internet Software and eServices Group
Lucent Technologies/Bell Labs Innovations 263 Shuman Blvd., Rm 1A-413
Naperville, Illinois 60566 Voice: +1 630 224 0216 Fax: +1 630 713 0184
_______________________________________________
Sip-implementors mailing list
[EMAIL PROTECTED]
http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
