Hi,
With contact headers and record routes, I don't know if it could
happend, but if the ACK got cought in a loop the Via headers are needed
to detect that...
Just a thought.
Regards,
Christer Holmberg
Ericsson Finland
Ramachandran Iyer wrote:
>
> thnx for ur response vijay..
>
> i understand that the rule for processing request
> mandates the insertion of Via..
>
> but is it just for sake of the rule that we need the
> via in ACK.. wherein in other places via makes sense..
> and is needed..
>
> is it fair to say that we necessarily dont need the
> via: in ACK for proper functioning..(assuming the
> server does'nt crib about the missing via: in ACK)
>
> rama
>
> --- Vijay Gurbani <[EMAIL PROTECTED]> wrote:
> > 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
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> >
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