Subject: [Ecrit] Routing of calls based on location

From: "Brian Rosen" <[email-masked]>
Date: Wed, 19 Jul 2006 17:23:44 -0400

NOTE: THIS MESSAGE IS COPIED TO SIP AND ECRIT, IF YOU REPLY, SEND IT ONLY TO
GEOPRIV

The SIP Location Conveyance document anticipates the ability to route a call
based on the location of the caller.  The original impetus for this is
emergency calling.  In ecrit, a mechanism has been defined (LoST) that takes
a service request (in the form of a newly defined service urn) and a
location and returns a URI.  This mechanism is not limited to emergency
calling, and could be used for arbitrary location based routing by defining
new service urns.

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.  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).

We propose to explicitly allow hop-by-hop security when sending location
using SIP for the purpose of location based routing.  We will specify you
MUST use TLS if sending location by reference (and there will be some words
about the choice of URI construction which is raised in another email I am
about to send).

An important issue that we need to discuss is what "Do Not Distribute" means
in this case.  We would like it to allow the data to be passed onward.
Indeed, SIP proxies shouldn't be dropping headers.  We propose that it means
that it cannot be distributed except that the location header (and body of
course) is passed as it normally would.

Note that although this is an issue that concerns the SIP working group,
because the location conveyance document is a sip document, it really is a
geopriv issue.  It also affects ecrit, since we are using its protocol
beyond its initial purpose.  We ask that this discussion be held on the
geopriv list, and not copied to either sip or ecrit.

Brian

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