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

[Paul Kyzivat <[e-mail]>]

James,

I have not been following this discussion closely, so apologies if this 
comment doesn't make sense...

It seems like a key issue is understanding *who* will need location 
information for routing purposes, and how it is that they would know 
that they should do so.

I don't think a UAC will be inserting location information in every 
call, so it must have some way of knowing that it will be needed for 
some purpose. Has there been any discussion of that? (If I just dial the 
number for Pizza Hut, my phone won't know. Either I must press some 
special button that says to include location, or else there must a 
response from downstream to the first request indicating that location 
is needed. If the specification of "recipient" must be included, then 
that error response will need to indicate the desired purpose. And then 
the UAC will still have to decide if it is ok to include this.

Next, lets take the Pizza Hut case. If I am calling 
sip:[e-mail], then to me pizzahut.com *is* target 
destination. It is probably not difficult for me to decide if I want to 
give pizzahut my location or not. And it is probably irrelevant to me 
whether it is so that the closest branch can be selected for routing, or 
if it is so the pizza can be delivered to me. *If* Pizza Hut wants to do 
routing based on location of caller then it will be done at or 
downstream from pizzahut.com.

The significance of recipient=routing-entity only seems to make sense if 
it is used for routing *before* reaching pizzahut.com. But I don't see 
that as a very valid or plausible use case - at best it is meddling by 
SPs that IMO they ought not be doing.

Perhaps that is more significant and valid if the destination is a 
service URN - e.g. urn:service:pizza. The translation from from a 
service urn to a URI might be a valid reason to use location 
information, and might be done by any routing entity. Its also 
predictable by the UAC that location might be needed for this.

But maybe that isn't a real distinction. With the URN, in effect any 
node on the route can decide to take on the role of translating the URN. 
If it does, then it is in effect the intended recipient of the request.

I don't have a clear suggestion here, but IMO the distinction among 
categories of users of location information seems not quite right.

	Thanks,
	Paul

James M. Polk wrote:
> At 11:35 AM 11/22/2007, Hannes Tschofenig wrote:
>> Hi Daniel,
>>
>> daniel grotti wrote:
>>> I believe that if a UA puts "recipient=routing-entity" paramenter 
>>> into locationValue, the location information should be read only by 
>>> Proxy Server for location-based routing. But if a UA wants its own 
>>> location information to be known and seen by endusers, then UA have 
>>> to insert the "recipient=endpoints" paramenter. In this case Proxy 
>>> server, from my view, should only forward the message to the 
>>> destination. UA would just like to bring its own location to an 
>>> endpoint, and    could not interested in location-based routing.
>>>
>>> Does this make sense?
>>>
>>>
>>
>> Correct and makes sense.
>>
>> The recipient parameter is just a hint for processing.
> 
> Ted's tone doesn't indicate this is "just a hint", he's making this seem 
> like a mandatory prevention mechanism.  That I think is a fool's errand, 
> and it is not enforceable in cleartext.
> 
> That said, "hinting" that proxies SHOULD NOT view location when 
> "recipient=endpoint" is not a problem.  What I am resisting, is that 
> UA's don't know if a message might need location to route the message to 
> the endpoint. Contacting a UAS, like Pizza Hut, might need location to 
> route the message to the nearest store, the user might know this, but 
> the UA might not. This would result in a rejection of the initial 
> message (because location isn't readable by a proxy that needs the 
> location-info). Would the UA understand that the rejection means sent 
> "recipient=both" in a subsequent request? Or does the implementation of 
> that UAC need to prompt the user to acknowledge this is necessary to 
> complete the call set-up?  This seems to me to be complicated and 
> against normal user behavior, and I'm thinking about whether or not this 
> is being expected to become normal user behavior?  I think this might be 
> preventing calls to any store/service that implements a network routing 
> plan based on the UAC knowing where it is to route the call to the right 
> destination. I cannot understand how this would be differentiated by users.
> 
>> It does not have security properties.
> 
> I agree
> 
> 
>> Ciao
>> Hannes
>>
>>
>>
>>> Regards,
>>> Daniel
>>>
>>>
>>>
>>>
>>> -----------------------------
>>>        Daniel  Grotti
>>> DEIS - Universita' di Bologna
>>> -----------------------------
>>>        Via Venezia, 52
>>>   47023 Cesena (FC) - ITALY
>>> -----------------------------
>>> email:[e-mail]
>>> -----------------------------
>>>
>>>
>>> -----Messaggio originale-----
>>> Da: Ted Hardie [mailto:[e-mail]]
>>> Inviato: gio 11/22/2007 12:36
>>> A: James M. Polk; daniel grotti; IETF SIP List
>>> Oggetto: Re: [Sip] a question about IETF draft location conveyance 09
>>>
>>> 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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> 
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