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Re: [Ecrit] LoST

Subject: Re: [Ecrit] LoST
From: Hannes Tschofenig
Date: Wed, 11 Jul 2007 11:54:38 +0200
Hi Martin,

Dawson, Martin wrote:
Thanks Hannes,

Yes, I'm suggesting that since the profile spec is about to go RFC, that
the LoST spec might just as well reference it so we have a consistent
ecology of specs. I think that having a subsequent spec make the profile
mandatory would only be an issue if it came after LoST was implemented.
On the other hand, if we assume it will happen before LoST is
implemented, then why not just include the requirement now.
I would like to let the group decide.

With respect to GPS - a LIS (LCS, whatever) could utilize any suitable
protocol, including SUPL, to do GPS interactions with the client - it
still casts the result as a PIDF-LO in the response. I'm not really
thinking of the situation where the device does a GPS fix or gets it
from some other non-PIDF-LO source. In that case, I'd certainly agree
that the device may as well transcode it into the basic form. I'm not
really concerned about that situation.

I know about this feature in SUPL.
Still, do most GPS devices today use SUPL?


Ciao
Hannes

Cheers,
Martin

-----Original Message-----
From: Hannes Tschofenig [mailto:Hannes.Tschofenig@xxxxxxx] Sent: Wednesday, 11 July 2007 7:33 PM
To: Dawson, Martin
Cc: Winterbottom, James; ECRIT
Subject: Re: [Ecrit] LoST

Hi Martin,

Dawson, Martin wrote:
Hi Hannes,

This seems a bit bogged down in the here and now... A LIS for almost
any
access technology, with or without GPS, could produce a geo-shape as a
consequence of the location-determination technique it employs. What
3GPP may be thinking now doesn't seem particularly pertinent.
True. A LCS (this is the correct terminology now) can indeed produce a PIDF-LO with the Geo-Shapes format.

When you use a GPS receiver today (and probably for a long time) then it

does not produce a format in XML format since there is just no LCP involved.

There's already a pdif-lo-profile draft ([sic] is the spelling ever
going to get corrected btw or is a title immutable?) that states what
shapes should be used and defines what the LIS clients can expect to
receive.
We decided not to change the file name. When the document gets published

as RFC then the filename does not matter anway.
Btw, we recognized the wrong spelling with version -04 or so.

While I accept that a LoST implementor could add support for that
profile, as long as it is optional to do so, the client cannot be sure
that anything other than a point will be supported.
A new document can also say that the new location profile is mandatory to implement. Do you think that will be a problem?

 This adds the dual
issue of making the client always convert to a point form and/or
eliminating the prospect of LoST servers being able to do more
sophisticated routing based on weighted coverage by uncertainty.

Rather than invite the compatibility issue at a later date, wouldn't
it
be more prudent just to add the requirement now?
No doubt that we could add an additional location profile right now.

I am just repeating what we agreed earlier in the working group on this particular issue. If the working group now thinks that this is a problem

then we should re-consider it. I just want to open-up previously closed or postponed issues too quickly.


Ciao
Hannes

Cheers,
Martin

-----Original Message-----
From: Hannes Tschofenig [mailto:Hannes.Tschofenig@xxxxxxx] Sent: Wednesday, 11 July 2007 6:55 PM
To: Winterbottom, James
Cc: ECRIT
Subject: Re: [Ecrit] LoST

Hi James,

Winterbottom, James wrote:
Hi Hannes,

That makes perfect sense.

The issue that I am most concerned about is the limitation in the
shape
representation in the basic location profile. As it currently stands
I
cannot use standard GPS related shapes, my end-point has to interpret
location and put into a profile. This is incompatible with a large
number of solutions deployed today on which many deployments will be
based, at least initially. I strongly urge this WG to reconsider this
restriction and include circle, and ellipse at a minimum.
Some time back we also discussed this issue and the conclusion was the

following:
* Let us build a mechanism in there to have a mechanism to extend the location shapes.
* Let us specify simple location shapes first.

I know that there is this limitation with geodetic shapes and a
separate
location profile would be needed to address GPS and the cellular
world.
On the cellular aspect we also had a discussion with the 3GPP. There they are currently not using LoST at the end point since they are focusing on a different architecture (see
http://tools.ietf.org/html/draft-tschofenig-ecrit-architecture-overview-
00). Even if they would use LoST at the end point they most likely want to hide the location information of the end point or to make use of information like cell ids (as recorded in the issue tracker a while
ago:
http://www.tschofenig.com:8080/lost/issue16).

Now, everything boils down to the question of GPS. Since GPS produces data in a format that is not PIDF-LO alike we can already assume that the end host has to understand the format. It can now encode it in different ways. In previous discussions a couple of us wanted to add a

polygon as a location profile to the LoST document since it would also

address the location hiding requirement. Since this issue came also up

in the location hiding context we postpone this topic entirely.

Hence, it is up to us to come up with a location profile that supports
* a circle
* an ellipse
* a polygon,
* a combination of the above
* cell-ids
if we think there is a need todo so.

Ciao
Hannes

Cheers
James

-----Original Message-----
From: Hannes Tschofenig [mailto:Hannes.Tschofenig@xxxxxxx]
Sent: Wednesday, 11 July 2007 4:58 PM
To: Winterbottom, James
Cc: ECRIT
Subject: Re: [Ecrit] LoST

Hi James,

let me pick a concrete example: LoST server discovery.
Currently, we have specified the usage of DHCP and DNS. Only the
former
allows to discover the LoST server in the access network. I am,
however,
aware of the work on HELD discovery, see

http://tools.ietf.org/wg/geopriv/draft-thomson-geopriv-lis-discovery-
01.txt,
that aims to discover a HELD server in the access network using DNS
mechanisms.

Now, even though the current LoST draft does not describe how to
discover a LoST server using DNS in the access network that can be
extended later when the above document is generalized (which I think
would be a good idea).

Does that make sense to you?

Ciao
Hannes

Winterbottom, James wrote:
Hi Hannes,

What exactly do you mean by postponed?

Cheers
James





-----Original Message-----
From: Hannes Tschofenig [mailto:Hannes.Tschofenig@xxxxxxx]
Sent: Wednesday, 11 July 2007 5:58 AM
To: ECRIT
Subject: [Ecrit] LoST

Hi all,

during the WGLC we have received a number of comments. Then, we

delayed

the completion of the work because of the location hiding
discussions.
Now, you can find the latest version of the document at:


http://www.tschofenig.com/svn/draft-ietf-ecrit-lost/draft-ietf-ecrit-los
t-

06.txt

We have also updated the DHCP-based LoST discovery draft (based on
the
comments we received from the DHC working group). The document can
be
found here:


http://www.tschofenig.com/svn/draft-tschofenig-dhc-lost-discovery/draft-
ietf-ecrit-dhc-lost-discovery-02.txt

Now, here is the unfortunate news: It seems that we did not submit
the
LoST draft :-(
Everyone was assuming that someone else is going to submit it.

Ciao
Hannes

PS: James has recently sent a number of comments. Some of them got
reflected in the document (namely the editorial onces). Others got
intentionally postponed since we discussed them already in the
past.
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