RE: [Sip] RE: Delivering request-URI and parameters to UAS via proxy

"Elwell, John" <john.elwell@siemens.com> Tue, 15 January 2008 11:50 UTC

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Date: Tue, 15 Jan 2008 11:50:41 +0000
From: "Elwell, John" <john.elwell@siemens.com>
Subject: RE: [Sip] RE: Delivering request-URI and parameters to UAS via proxy
In-reply-to: A <CA9998CD4A020D418654FCDEF4E707DF0410E399@esealmw113.eemea.ericsson.se>
To: Christer Holmberg <christer.holmberg@ericsson.com>, Francois Audet <audet@nortel.com>
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Christer, 

> -----Original Message-----
> From: Christer Holmberg [mailto:christer.holmberg@ericsson.com] 
> Sent: 15 January 2008 10:41
> To: Elwell, John; Francois Audet
> Cc: sip@ietf.org; Paul Kyzivat; DRAGE, Keith (Keith)
> Subject: RE: [Sip] RE: Delivering request-URI and parameters 
> to UAS via proxy
> 
> 
> Hi John,
> 
> >I guess what still confuses me is, when both Target and P-CPI 
> >are used, which comes first, i.e., which represents the 
> >earlier target? When I read the draft, I thought Target was 
> >earlier. From various clarifying emails I now get the 
> >impression that Target is later. Can you confirm?
> 
> I am not sure what you mean by "earlier" target. 
[JRE]Assuming that the target changes as the request progresses
downstream, I meant the one that occurs first.

> 
> Target, if present, always represents the current target. A receiving
> entity that receives a request without a Target header has to assume
> that the Request-URI represents the current target. When no Target
> header is available on the request then the Target is inserted when a
> reroute is performed.
> 
> P-CPI is ONLY used to maintain the R-URI which is rewritten by the
> contact of the UAS. I.e. by the home proxy which is usually at the end
> of a chain of proxies.
> 
> When both Target and P-CPI are used: Target always represents the
> current target. P-CPI always represents the AOR received by the home
> proxy which may in some cases be the same as the current target but it
> may also be the last route (not equal to the current target) taken to
> deliver the request. 
[JRE] I think I am getting there. So the target could be some sort of
call centre group, for example, and P-CPI could be the AoR of the
selected member of that group. Correct?
I am a little concerned about using the term "AoR" in the definition of
these AoRs. What about a request targeted at a GRUU? I would imagine the
Target and P-CPI would both contain the GRUU, which is not an AoR.

John
 


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