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

From: Richard Barnes ^lt;>
Date: Thu May 10 2007 - 10:26:46 EDT


I certainly agree that our foundational documents are due for revision.
  However, until that revision is done, our work needs to be consistent
with those documents, even the parts we'd like to revise.

As to forwarding at layer 3: This seems like a valid distinction to me.
  Regardless of whether location is involved, by submitting a message
for store-and-forward processing, the user implicitly authorizes the
network to deliver that message to the proper recipients via necessary
relays. In SIP, the recipients are UASs and the relays are proxies on
the signaling path. This is the extent of the authorization.

What a store-and-forward transmission does not do is authorize
transmission outside the store-and-forward network, e.g., to LoST
servers or Google Maps. This needs to be explicitly authorized (by
something in the LO or by a tag in the header).


Henning Schulzrinne wrote:
> I should probably heed Ted's advice, but can't resist: privacy is all
> about distribution and access to information; it has nothing to do with
> processing. According to your logic, it would be perfectly ok to
> multicast the LO to anybody, given that it would only be
> stored-and-forwarded at layer 3. I have to admit that I find the
> distinction between a protocol 'reading' the LO when it does normal SIP
> protocol processing and when it invokes some logic to be a stretch and
> not supported by anything having to do with privacy.
> I think the discussion shows that our foundational documents lack
> clarity and motivation, as they don't actually explain the goals and
> provide guidance that corresponds to these goals (presumably, privacy
> from third parties).
> Henning
> On May 9, 2007, at 5:29 PM, Richard Barnes wrote:
>> Ok, we're back to this:
>> The difference is in whether the proxy is a Recipient of the LO. If
>> it passes the bits along blindly, without interpreting them, then it
>> has not, for privacy purposes, received the LO. This is why you can
>> pass an LO with retransmission-allowed=no through a store-and-forward
>> network (be it SIP, email, whatever).
>> If the proxy reads and acts on the LO, then it becomes a Location
>> Recipient, and is bound by the privacy rules in the LO (and possibly,
>> as we've discussed, in the SIP header). Then, if
>> retransmission-allowed=no, that indicates that the proxy should not
>> send the LO -- or the LI within it -- to another party. And, as I've
>> discussed before, there's some flexibility in "party", but there's no
>> sensible definition that allows arbitrary LoST queries.
>> The trouble with -conveyance is that it allows both UASs and proxies
>> to be the recipients of the location, even though the UAC might want
>> to send different locations with different privacy rules to these two
>> different sets of recipients. I think indicating destinations (with
>> header fields or tags) is a simple way to disambiguate this.
>> --Richard

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