Subject: [Geopriv] Consensus on changes to location-conveyance

From: "Rosen, Brian" <[email-masked]>
Date: Tue, 25 Jul 2006 13:38:11 -0400

I have put out a number of emails on proposed changes to location
conveyance.  Some of them have sparked a number of comments.  My summary
of consensus on these issues is:

1. We proposed to explicitly disallow use of a Data URI, which would
allow specification of a Location-by-value in a header.  There was a lot
of list traffic on this, currently in the state where Keith asked for a
real use case for it.  So far, we don't see a use case that cannot be
provided by location-by-reference in a header.  If we don't get a good
use case, I think consensus is to disallow location-by-value in a
header.

2. Dereferencing location-by-reference.  We had initially proposed to
document a process to use a raw HTTP(S) Get to dereference.  There was a
lot of discussion, and then I made a new proposal, see item 6. 

3. We proposed to allow a Reason header with a 424 Bad Location
response.  This seems to be acceptable to the WG.  Geopriv will create
and populate the registry in a separate draft.

4. We proposed to explicitly allow hop-by-hop TLS security for location
when the endpoint wished to allow routing based on location.  We further
proposed to interpret "Do not Distribute" flags as allowing sending of
the location to the routing database (LoST for example).  Hannes pointed
out that there was a proposal to allow two Location headers, one of
which could be used for routing and another for onward forwarding to the
recipient.  Hannes' message seemed to agree that "Do not distribute"
would allow sending of the location to the routing-by-location database,
but would obligate the proxy that did that to remove the location before
it forwarded the message.  There were no other messages on this thread.
We conclude that allowing hop-by-hop security for location based routing
is acceptable, and Do Not Distribute DOES allow forwarding to a routing
database, but requires that the proxy doing the location based route to
remove the location it uses for that purpose.

5. We proposed to create a parameter and a registry to distinguish
multiple ways to dereference a location where HTTP(S) was the transport.
Resolution of this issue depends on resolution of issue 6.

6. We proposed to allow sip/sips and pres: in the location header.  I
later speculated that if we allow this, it forms a simple way to do
location-by-reference, and we could eliminate the raw HTTP(S) Get
proposal, with the parameter and registry entirely.  There was some list
traffic in favor of this.  Martin Thompson is skeptical that SIP
Presence Subscribe/Notify is actually allowed as a geopriv "using
protocol".  Several of think that it is.  If we don't get any more
comments on this proposal, we will allow sip/sips and pres, not have any
http(s) resolution text, and not propose a parameter and accompanying
registry.

If this does not reflect your position, please speak up now.

Brian

_______________________________________________
Geopriv mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/geopriv

---

From: Ted Hardie <[email-masked]>
Date: Tue, 25 Jul 2006 11:18:43 -0700

>it forwarded the message.  There were no other messages on this thread.

Actually, I commented on the same problem, though it may have been
connected to one of the related threads; here's the text of that message:

>At 5:23 PM -0400 7/19/06, Brian Rosen wrote:
>>NOTE: THIS MESSAGE IS COPIED TO SIP AND ECRIT, IF YOU REPLY, SEND IT ONLY TO
>>GEOPRIV
>>However, this opens up the issue of geopriv privacy concerns because the
>>sender does not know the identity of the element (proxy) that will route the
>>call using LoST.  It may be that the UAC itself does this, but it may be
>>some other intermediary.
>>
>>If the identity of the intermediary is not known, then protecting the
>>location information becomes more difficult, because we cannot encrypt using
>>keying material from the intended recipient.
>
>Just to mention this, it appears to also rule out the idea of encrypting
>with the user's key, since there is no way of knowing whether the "intended
>recipient" has that key material either.  Intended recipient is actually
>a bit of a problematic term here, since it's really the on-path network elements
>which consume the information.  They aren't the intended recipient of
>the communication, they are the recipients of the signaling (of which location
>is now a part).
>
>This is a bit confusing because it seems to be possible to include a
>"re-transmission allowed"  rule with a value of "no" (intended to be
>consumed by the "intended recipient" of the underlying communication),
>while still wanting to allow the location to be passed along the path.
>
>>In fact, we would need to use
>>hop-by-hop security, with transitive trust.  This is what the emergency case
>>does, but it also allows no channel security if necessary (usually meaning,
>>try it with TLS and if that fails, try again without TLS).
>
>While I certainly encourage hop-by-hop security, I don't think it really
>meets the geopriv privacy concerns.  I think you  have to have some way of
>expressing "re-transmission for routing permitted" (and likely retention
>limited), since that is a separate statement.
>
>Just typing aloud here, but could we come up with a way to use an
>external ruleset to express this?  With an embedded cid, that would
>not actually require dereferencing.
>					Ted
>

>remove the location it uses for that purpose.

To reiterate this, I do not believe that this is sufficient; I think you have to
have some way of saying "re-transmission for routing permitted" before
you meet the geopriv privacy concerns.

>Resolution of this issue depends on resolution of issue 6.

I believe that an HTTP GET of a PIDF-LO object is a reasonable baseline.
Saying that other mechanisms should update this document with their
dereferencing mechanisms if they could be confused with the baseline
seems to me to be sufficient.  I'm not sure a registry is needed.  In practice,
I don't think we would hit the interoperability problems often. These days,
extensions to HTTP commonly use different  mime types to indicate the special
handling, and I expect anyone creating a more feature-rich dereferencing
mechanism built on HTTP would not end up using pidf-lo.  

That means the "uri confusion" aspects of the discussion are probably not
that severe.  The only issue is if someone supports only the more feature-rich
alternative and not a baseline GET of the pidf-lo.  I think we should
discourage that, by establishing a real baseline.

Note also that HTTP URIs don't indicate the HTTP Method directly; often they
support multiple methods (e.g. HEAD and GET).

>http(s) resolution text, and not propose a parameter and accompanying

I share some of Martin's skepticism here, but I won't fall on my sword
if the WG goes in this direction.

Thanks for the clear set of issues and opportunity to comment,
				
					Ted Hardie

---

From: "Marc Linsner" <[email-masked]>
Date: Tue, 25 Jul 2006 15:29:13 -0400

In-line..... 

> -----Original Message-----
> From: Rosen, Brian [mailto:[email-masked]] 
> Sent: Tuesday, July 25, 2006 1:38 PM
> To: [email-masked]
> Cc: [email-masked]
> Subject: [Geopriv] Consensus on changes to location-conveyance
> 
> I have put out a number of emails on proposed changes to 
> location conveyance.  Some of them have sparked a number of 
> comments.  My summary of consensus on these issues is:
> 
> 1. We proposed to explicitly disallow use of a Data URI, 
> which would allow specification of a Location-by-value in a 
> header.  There was a lot of list traffic on this, currently 
> in the state where Keith asked for a real use case for it.  
> So far, we don't see a use case that cannot be provided by 
> location-by-reference in a header.  If we don't get a good 
> use case, I think consensus is to disallow location-by-value 
> in a header.
> 

I see a problem here.  Location-by-reference is nothing more than 'magic
happens here'!  Please point to a wg item documenting the
location-by-reference mechanism.  How can you state the
location-by-reference will cover all the use cases that the Data URI would
when location-by-reference hasn't even been defined anywhere?  You're
loading up the magic with a lot of assumptions.  Location-by-reference is an
individual submission as a solution to a set of requirements that haven't
been fleshed-out in geopriv.  

I believe that Henning/Hannes also recognized this issue, hence the
suggestion of a Data URI.  Dismissing this suggestion based on an already
accepted non-existent mechanism seems like getting the cart before the
horse.

..........snip

> 6. We proposed to allow sip/sips and pres: in the location 
> header.  I later speculated that if we allow this, it forms a 
> simple way to do location-by-reference, and we could 
> eliminate the raw HTTP(S) Get proposal, with the parameter 
> and registry entirely.  There was some list traffic in favor 
> of this.  Martin Thompson is skeptical that SIP Presence 
> Subscribe/Notify is actually allowed as a geopriv "using 
> protocol".  Several of think that it is.  If we don't get any 
> more comments on this proposal, we will allow sip/sips and 
> pres, not have any
> http(s) resolution text, and not propose a parameter and 
> accompanying registry.

I certainly think it's more prudent to define the dereferencing mechanism
prior to making claims about the protocol.

Do I believe location-by-reference will happen?  Probably, but making
assumptions about the mechanism now is quite premature.

-Marc-

---

From: Andrew Newton <[email-masked]>
Date: Tue, 25 Jul 2006 16:21:44 -0400

> assumptions about the mechanism now is quite premature.

Perhaps nothing will save us.  We've had by-value since step one, and  
now by-value take 2 is being proposed.

-andy

---

From: Hannes Tschofenig <[email-masked]>
Date: Thu, 27 Jul 2006 16:33:59 +0200

Hi Brian,

I guess you are only talking about the current Location Conveyance 
document.

> use case, I think consensus is to disallow location-by-value in a

I don't agree with your statements but I am (in the meanwhile) convinced 
that we need to cover this in a separate document.

> remove the location it uses for that purpose.

Ok.

> http(s) resolution text, and not propose a parameter and accompanying

I disagree with location-by-reference being added to the document (or 
suggest to get it removed from the document).

Ciao
Hannes