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

["James M. Polk" <[e-mail]>]

At 05:36 PM 11/21/2007, Ted Hardie wrote:
>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.

I think this is what we disagree about.  Aside the emergency 
scenario, it is there types of requests that I find it a little hard 
to believe a UA will know that a "routing-entity" will not be needed 
to get the message to the ultimate UAS. How can the UA logic know 
that when calling Pizza Hut or a specific verses nearest garage needs 
to have location used or not?

This almost makes a practical use of this parameter (and this 
RFC(to-be) to RECOMMENDED that "recipient=both" is the default unless 
the UAC _knows_ it doesn't want a server ("routing-entity") to view 
the location.

>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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