The SIP proxy gets a location URI via SIP. Now, it wants todo location based
routing for the emergency call. It will dereference the location URI as you
mention in Section 4.5 of your document. The LIS does not know that this is
request is only for location sufficient for routing and it tries to
determine location at a best possible extend. This takes time. Then, when
location is available the NOTIFY is sent. The SIP proxy can route the call
but had to wait longer (potentially longer than Brian states in Phone BCP
regarding the maximum call setup time).
If I understood the HELD mechanism correctly then there is a way to indicate
what type of reference the URI should point to (this relates a bit to the
HELD context document). And the same stuff is available in HELD deref as
well.
Now, I was wondering whether this would be useful in
draft-ietf-geopriv-loc-filters-05.txt as well. Namely, to let the SIP proxy
tell the LIS when it sends a SUBSCRIBE that it wants location for routing
(and that typically means faster>
If it does not make sense to anyone then I remove it from
draft-ietf-geopriv-loc-filters-05.txt.
Ciao
Hannes
>-----Original Message-----
>From: James M. Polk [mailto:jmpolk@cisco.com]
>Sent: 28 July, 2009 13:02
>To: Hannes Tschofenig; 'Thomson, Martin'; geopriv@ietf.org
>Subject: RE: [Geopriv] Another Update to
>draft-ietf-geopriv-loc-filters-05.txt
>
>At 11:54 AM 7/27/2009, Hannes Tschofenig wrote:
>>Hi James,
>>
>> >> >More seriously: I'm not entirely sure how to interpret
>> >> >responseTime in the context of a SIP PA. This might work as you
>> >> >have described, but I would suggest that it complicates things
>> >considerably. There's
>> >> >discussion on this point in my draft here:
>> >> >
>> >>
>><http://tools.ietf.org/html/draft-thomson-simple-cont-presence->va
>> >> >l
>> >> -req-02#section-4.6.1.1>
>> >> >
>> >> >I don't know how to solve this problem yet.
>> >> >
>> >>
>> >>I am not sure I see the problems.
>> >>
>> >>Imagine a SIP proxy receives a SIP message with an LbyR
>and wants to
>> >>retrieve location information for routing. Depending on the
>> >URI scheme
>> >>(HTTP vs. SIP) he would either use
>> >>http://tools.ietf.org/id/draft-winterbottom-geopriv-deref-prot
>> >ocol-03.t
>> >>xt
>> >>Or
>> >>http://www.ietf.org/internet-drafts/draft-ietf-geopriv-loc-fil
>> >ters-04.t
>> >>xt
>> >
>> >I'm confused.
>> >
>> >For SIP, why would the filters doc be used when Conveyance already
>> >has how a server dereferences a location URI for routing?
>> >
>> >This isn't a soliciting action requiring filters.
>>
>>How does SIP Location Conveyance dereference location URIs?
>>My reading of draft-ietf-sip-location-conveyance was that it conveys
>>location by value and/or by reference.
>
>I have a section on this. Specifically it is section 4.5
>
> "Using sip/sips/pres as a Dereference Scheme"
>
>I even have a pretty diagram.
>
>
>>What "indication" is used in a SIP SUBSCRIBE to indicate "Please give
>>me location information suitable for routing."?
>
>err, a proxy routes based on the location information it is
>given (if it initiates a dereference transaction in the first
>place, there is no "suitable-ness" to it.
>
>The location-based routing process asks for, and receives (or
>not) the PIDF-LO of the Target, then processes the message
>(i.e., making routing decisions) as if it were sent the
>PIDF-LO in the original SIP request. There's no magic to a
>location URI to get a routable location vs. an unroutable
>location -- especially since there is no difference in our
>that same proxy receives location by value.
>
>If you believe there needs to be a suitable-ness to location
>information, then we need a new error code for cases in which
>the supplied location isn't suitable, with exactly what an
>inserter is supposed to do with that error code (i.e., in that
>error code, there needs to be an indication what was missing -
>other than the whole location - that needs to be in the
>subsequent SIP request to make is worthy of being routed.
>
>Which do you want -
>
>#1 - route based on the available location supplied (by-value
>or by-reference)?
>or
>#2 - a new error code and inserter behavior to know what to do
>when insufficient location was provided in the initial SIP request?
>
>#1 is easy, cuz that's the way Conveyance is written now.
>
>#2 is much more complicated - both to the routing proxy, and
>the burden on the location inserter to understand what isn't
>enough location, and to correct for just that amount - to
>satisfy the proxy's determination of what it thinks it needs
>to route the message propoerly.
>
>James
>
>
>>Ciao
>>Hannes
>
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