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

From: Ted Hardie ^lt;>
Date: Mon May 07 2007 - 15:04:45 EDT

At 7:45 PM -0400 5/6/07, Henning Schulzrinne wrote:
>>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:

This isn't how all of us see this, Henning.

Imagine for a moment that we had created two headers: Routing-location: and Recipient-location: . We might have done that in order to allow the routing location
to be at a different level of precision than the location sent to a recipient, or to
disambiguate the two cases in the current location conveyance document
(intended for the end user and location-based-routing). If we had, the presence
of a Routing-location: header certainly would be sufficient indication that the
message sender was willing to have the message routed using location.
It would be stating, in essence, that the SIP proxy engaged in the location-based
routing was the intended recipient. The absence of that header might also be
sufficient to say that the proxy should not do so, as delving into a
"recipient-location:" header for data when there would be another place for
routing location to go would be more clearly reading a location object
intended for a different recipient.

That's not the current proposal, which uses the same header for two different use
cases. Since those use cases involve different intended recipients (the end recipient
and the SIP proxy which might do location-based routing), there is some ambiguity.
Using an explicit parameter for routing location gets us to the state where the
permissions can be disambiguated without having to have two headers.
Having two headers would do that too, but it's yet more stuff to carry around.

As you know by now, some of us do believe that there is an important distinction
between using standard SIP mechanisms to carry the location to an end-user
(case one, for which retransmission=no seems to work for everyone,
since the SIP proxy is just acting to forward the message) and examining the
header and managing the routing based on it (case two, for which some of us
have argued an explicit retransmission="routing-permitted" would be valuable).
Allowing "retransmission=no" to allow location-based routing via whatever
means eliminates the user's ability to distinguish between those and weakens,
at least in my opinion, the user's control over location.


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Received on Mon, 7 May 2007 12:04:45 -0700

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