If Route Header is field is present in INVITE then ACK MUST be sent to the
first element of Target Set (which will be the the same element to which the
original INVITE was sent).

ACK is NOT matched to Server Transaction as Server Transaction is destroyed
the moment UAS passes it a 2xx response.

ACK will rather be matched to the Dialog at UAS.

Regards,
Salman

-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of M.
Ranganathan
Sent: Friday, September 20, 2002 6:23 PM
Cc: [EMAIL PROTECTED]
Subject: Re: [Sip-implementors] Signaling path for ACK (RFC 2543 vs RFC
3261)


One more clarification:

If I understand correctly,  provided the INVITE  had Record-Routing 
enabled then the ACK  must traverse the same set of  proxies and if not, 
the ACK can go directly to the UAS. If the INVITE was Routed through 
another set of proxies (for example, if it had a Route header)  and the 
ACK is now directly sent to the UAS  the top via haeder of the ACK will 
be different from the top via header of the original INVITE  received at 
the UAS  (but the first via header of the invite will, however match)  
so how do we find the server transaction corresponding to the ACK? 
Should I look at the first via header when record routing is not enabled 
and last via header when record routing is enabled ? Will this always work?

Thanks.


Ranga.

Brett Tate wrote:

>>For an INVITE transaction, MUST the 
>>ACK traverse the same signaling path
>>(i.e. set of intermediate proxies) 
>>as the  INVITE that is being ACKed
>>regardless of whether Record-Routing 
>>is enabled or not?
>>    
>>
>
>Concerning 2xx responses, a proxy must 
>record-route to receive the ACK.
>
>Concerning other final responses, the
>proxy should receive the ACK.
>
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>


-- 

M. Ranganathan
N.I.S.T. Advanced Networking Technologies Division 
100 Bureau Drive, Stop 8920, Gaithersburg, MD 20899
Tel:301 975 3664; fax:301 590 0932

Advanced Networking Technologies for the people!



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