Subject: [Geopriv] Radius-Geopriv: Precision

From: Tschofenig Hannes <[email-masked]>
Date: Wed, 2 Mar 2005 11:22:05 +0100

hi all, 

the text paragraph about precision raised some discussions, see below:

[lionel]
   Additionally, the Precision field provides further information about
   the location information provided via Radius.  For large networks
   information about the location of the user can be provided in
   different degrees of accuracy.  This field gives a hint.  Ideally the
   location of the user is returned to the home network but in some
   cases it might not be available.  It has to be noted that the user
   does not provide the location information itself.

==> (1) I don't understand the end of this paragraph! What kind of user
location are you referring  to here? Whatever the precision and the nature
of the location information, the location of the  user could always be
returned to the home network. Maybe you are talking about the location of
the  user's end point (which could be far away from the NAS)?

==> (2) only two formats of location information are defined at this
stage: civil and geospatial. What about some "location ID" that could be
sent to the AAA server to  retrieve location info? I mean that the location
info attribute may convey either explicit  ("self-explicit") location
information or any identifier if there is a mean for the receiver to
extract explicit information from this ID, such as the CellID in GSM.

[bernard]
I was confused about this as well.

[Hannes] regarding bullet (2): we do not provide some location id tokens
(such as cellids) with  our proposal. 

[lionel] 

     Precision (8 bits):
       Describes which location this attribute refers to:
       (0) describes the location of the NAS
       (1) describes the location of the AAA server
       (2) describes the location of the end host (user)
       (3) describes the location of the network

==> What is the meaning of the fourth value? How could it be possible to
have less than the NAS or  the visited RADIUS location information?

[hannes] the current format allows to specify location information very
precisely. if you have a  larger network you might want to indicate only the
location of the network rather than the  location of each access point
(particularly if we configure the loc-info of the access points  manually).
indicating the precise information of the aaa server might not always what
you want. in  this case you might indicate, for example, a city destrict as
a whole rather than indicating the  floor where the aaa server can be found.

maybe the aspect of precision needs some more text. maybe the terminology
needs to be changed. 

ciao
hannes

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From: "Brian Rosen" <[email-masked]>
Date: Wed, 2 Mar 2005 08:29:18 -0500

I think you need a new term.
Precision usually implies something related to accuracy, that is, what is
the range of error of the reported position.  That idea is useful, although
complicated.  Here, you aren't dealing with accuracy but with what,
precisely, is being located.  For example, you may have the location of the
NAS within .02 meters.  That's high accuracy, but may not be near the user.
So, I would use a term like: location-reference, and change the text
accordingly.

Brian

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On Behalf
> Of Tschofenig Hannes
> Sent: Wednesday, March 02, 2005 5:22 AM
> To: [email-masked]; [email-masked]
> Subject: [Geopriv] Radius-Geopriv: Precision
> 
> hi all,
>

---

From: Bernard Aboba <[email-masked]>
Date: Wed, 2 Mar 2005 05:59:42 -0800 (PST)

> maybe the aspect of precision needs some more text. maybe the terminology

I think the document needs to clearly differentiate NAS location from user
location.

Today shipping 802.11 APs can estimate the user location to a significant
degree of precision, and AAA server products are making
authentication/authorization decisions based on that information.

For example, in a secure 802.11 environment, it may be forbidden for
users to access the network outside of authorized areas.  Therefore the
RADIUS server may require the user's geospatial location in order to
determine if an Access-Request can be granted.

I'd note that in these situations it is even possible for the user's civil
location to be different from that of the NAS device.  For example, if
directional antennas are being used, the user could be a substantial
distance away from the AP.

If NAS location and user location are clearly delineated, then it will not
be necessary to take that into account within a precision attribute.

---

From: Jari Arkko <[email-masked]>
Date: Fri, 04 Mar 2005 14:48:09 +0200

>Today shipping 802.11 APs can estimate the user location to a significant
(snip)

>be necessary to take that into account within a precision attribute.
I agree. Here are some text suggestions. Change

     Precision (8 bits):

to

     Entity (4 bits):
        Describes whose location this attribute carries:
        (0) Describes the location of the user's client device,
             as estimated by the network.
        (1) Describes the location of the NAS

Justification: I could not think of any case where the location
of AAA server would have to figured out. Also, "NAS" and
"network" are too imprecise to be useful. What about a
distributed NAS, a concentrator/dummy AP combination?
I would just give a the user's location or no location at all
if we get into that kind of things. But if you really need the
network's location, you might consider adding a subfield
for "cell size", that shows how large area this "NAS" covers.
But I don't think its essential functionality.

--Jari