Thanks for reply Brian.
Probably we'll go for the SUBSCRIBE/NOTIFY option. We'd rather keep cell ids 
inside our network, but anyway it's not really possible (see Google's My 
Location). So far we won't have any 3rd parties connected to IMS though.

Do you know if there is any standard to include a cell-id into PIDF-LO?

Bartek


-----Original Message-----
From: Brian Rosen [mailto:[EMAIL PROTECTED] 
Sent: Wednesday, August 13, 2008 10:24 PM
To: Bartłomiej Kołakowski; [EMAIL PROTECTED]; [email protected]
Subject: RE: draft-ietf-sip-location-conveyance - Question about potential 
usage of the Geolocation header

You can use the "HELD" protocol, rather than a SIP SUBSCRIBE/NOTIFY for the 
dereference, if that makes it seem simpler to you.  SUBSCRIBE/NOTIFY is quite 
simple, and most devices and services implement it for other reasons.

We have discussed using cell-id as a representation mechanism, but have been 
told, many times, that operators will not divulge location of cell ids beyond 
the immediate network, which makes this form of location entirely
unsuitable for the range of applications we envisioned.   If you have
different information, please share it.

On the other hand, even if we did allow cell id as a form of location, it would 
be inside a PIDF-LO, and thus would need to be in a body.

I don't think putting actual location in the header is a good idea, as it 
cannot be protected against inadvertent disclosure.  That would be a problem in 
the IETF.

Brian
________________________________________
From: Bartłomiej Kołakowski [mailto:[EMAIL PROTECTED]
Sent: Wednesday, August 13, 2008 10:04 AM
To: [EMAIL PROTECTED]; [email protected]
Subject: draft-ietf-sip-location-conveyance - Question about potential usage of 
the Geolocation header

Hello,
I have got such concern regarding location conveyance in SIP messages: I am 
designing IMS Appilcation Server, acting as a proxy, that would query network 
elements for location information. As you wrote proxies cannot insert message 
body, so the only way is to provide location by reference.
This requires appling SUBSCRIBE-NOTIFY mechanism, which makes the architecture 
of the solution quit complex.
In order to make it simpler I thought about including location information as 
locationValue inside the Geolocation header. In fact we do not need location 
represented with coordinates, but with cell-id (that's mobile network). PIDF-LO 
does not support it, but maybe inside a header that would be possible? There 
would be also an issue in indicating loaction target whose location is included 
(we plan to include both A and B parties location). Geolocation header would 
look like this:
Geolocation: {cell-id-3gpp}
;location-target="[EMAIL PROTECTED]";inserted-by="[EMAIL PROTECTED]" 
What do you think about souch a usage of Geolocation header, maybe you could 
give us some other solution? 
Thank you in advance,
Bartłomiej Kołakowski
Service Solutions Architect
Service Development Support Department
Polkomtel S.A
tel. 601131509 

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