Re: [Sip] a question about IETF draft location conveyance 09

[Ted Hardie <[e-mail]>]

At 4:18 PM -0600 11/21/07, James M. Polk wrote:
>\
>Ted -- This header parameter is for a PIDF-LO, yes -- but it pertains to the SIP WG's expertise in knowing and agreeing with SIP's ability to foresee the type of topology from UAC to UAS, and each server (whether there even is one) in between.  I'm not so sure the SIP WG agrees that a UAC can make this determination, and am soliciting their input here in a broad way.
>
>Can a UAC understand enough about the topology of the Internet to understand where it is sending a request, including how SIP servers may or may not act upon that request?
>
>I believe, if the answer is no, the the "recipient=" parameter is a flawed SIP header parameter.
>
>If the answer is yes, then it stays with no further arguments from me.


I think we have fundamentally different ideas of how much understanding of the
topology this implies.  My view is that the header as currently specified says
either "This is meant for the person answering the call/taking the session" or
"This is meant to help get the call through/get the session to the right responder".
Within the latter case, it requires no knowledge at all of topology; it does
not distinguish among the many different routing elements which might be
trying to make that happen. 

A UA that does not care whether it is used for routing can enter "both"
and all is well.  A UA that *wants* it to be used this way can enter "routing-entity".
The availability of "endpoint" as a separate possibility makes sure that
an endpoint can indicate that use by the routing system is not intended. 
If the SIP community believes "routing-entity" is too vague
and needs to be broken out, I do not see how the GeoPRIV could object or
why it would want to; certainly this working group should have the final word
on that.  But collapsing things so that entering "endpoint" is
not an indicator to the routing entities that they should just pass things along
would find opposition (at the very least from me).  That would break a pretty
fundamental assumption that users are in control of the pidf-lo distributions.

Hope you have a great Thanksgiving,
				Ted


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