Re: [Geopriv] Location in SIP and "retransmission-allowed"

From: Henning Schulzrinne ^lt;hgs@cs.columbia.edu>
Date: Sun May 06 2007 - 19:45:33 EDT

>
> I'm sorry, nothing in the archive jumps out at me as a concrete
> proposal. Could I request a retransmission?
>

Let me try to be more specific, collecting thoughts across multiple
postings:

The goals are two-fold:

- achieve logical consistency that doesn't make artificial distinctions

- create predictable behavior that users can understand

We have agreed that no-forward does not affect the proxying of
location information by SIP proxies. There is no logical distinction
between routing SIP messages and copying a subset of the information
to some other protocol, from a privacy perspective. Bits are bits,
whether they are in XML or SIP bodies. Thus, even if we ignore the
privacy difference between identity-less location and LOs, there are
two possible logically consistent rules:

(1) Use of location information for call routing and proxying are
allowed if the information remains within the administrative control
of the domain named in the SIP request URI, as long as the
information flow is protected to the same extent as the SIP
signaling. (Thus, a SIPS call requires use of HTTPS for LoST.)

This covers the emergency calling and PizzaHut case since the LoST
hierarchy is operated by the same administrative entity (government
or PizzaHut) that is addressed by the request URI and avoids the
silliness that the PSAP can see the location and identity if it
arrives via SIP, but can't see the location only if it were to arrive
at the LoST server it operates.

Thus, retargeting to a different administrative domain or lookups
outside that destination domain require explicit permission.

A slightly more liberal interpretation is

(2) No explicit permission is needed when the operator of the SIP
proxy ensures that the data used for lookups remains private, even if
the data is handed to a third party (such as a governmental LoST
hierarchy).

The only other logically consistent rule is to disallow SIP proxying
and location lookups unless a flag is specified, but since such a
flag would need to be specified in almost all cases of practical
interest, this becomes essentially meaningless.

Henning

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Received on Sun, 6 May 2007 19:45:33 -0400

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