Subject: Re: [GEOPRIV] draft-winterbottom-location-uri-01

From: John Schnizlein <[email-masked]>
Date: Mon, 20 Feb 2006 15:43:53 -0500

A few comments on this draft:

On Jan 31, 2006, at 11:19 AM, Winterbottom, James wrote:

> An update to the Location Reference draft is available.
>  

section 1

    This document is intended to provide a guide to making a choice
    between the two approaches, as well as providing some additional
    information on providing LI by-reference.

It is not clear that a choice is required.  It may be that location 
by-reference has a different set of conditions under which it is 
useful.  Section 4 appears to identify a situation where by-value is 
better.

section 3

The claim that by-reference provides useful decoupling is not 
substantiated.  A (hypothetical) presence subscription could provide 
locations as well as references.  The location format similarly is 
independent of an additional de-referencing operation required by the 
proposal.  The presumption that Location Servers should translate 
between civic and geographic formats is a mistake because it could 
obscure which is the original and most precise format.  Errors in 
locating an address that are obvious to users of popular mapping web 
services should be avoided by the simple expedient of providing the 
best known location.  Location users can employ whatever degree of 
effort to get the level of precision in the translation appropriate to 
the application.

section 4

    Using Location URIs places the control over when location is
    generated with the LR.  Again, in a time-critical application this
    also means that the LR may be forced to wait for location generation
    to occur.

By-reference is neither necessary nor sufficient for the requester to 
control when location generation occurs.  A location server could incur 
the cost of a new generation when a request by-value occurs just as 
well, and a location server could de-reference without invoking a new 
location generation process.

section 4.1

Delegating responsibility from the host to a server in the network does 
appear to be the largest implication of by-reference.  It is worth 
considering whether this direction of shifting responsibility is 
consistent with the Internet model.  Moore's law, with its implied 
favor for ubiquitous rather than centralized computing, is expected to 
continue for another 10 years, based on technology in the pipeline.  
This is no time to abandon the guiding principle of the Internet that 
difficult decisions are best left to hosts at the edge of the network.

section 4.2

The implication that by-reference protects location values from threats 
of "open medium" is vacuous.  Before location is useful, the reference 
must be de-referenced to a value.  The requester then has the location 
(value) and can do anything it wants with it beyond the reach of 
whatever policy enforcement is in the location server.

section 5

The premise that references would be sufficiently stable where hosts 
are mobile is unjustifiable outside of legacy (pre-Internet) networks 
such as cellular phone service.  There is no reason to think that 
mobile Internet hosts would have their locations tracked inside the 
network.  The best authority for a mobile host's location is the mobile 
host with GPS available and getting cheaper, and with Galileo coming 
online to overcome some of GPS's limitations.

section 6

No security advantages of by-reference over by-value are claimed, but 
fraudulent location information is considered.  It remains unclear what 
the threat is, and it appears that misrepresenting the validity of a 
reference is as problematic as that of the location value.

Summary: it is unclear that all the complexity and work of by-reference 
is justified by the ability to pass references through untrusted 
intermediaries.  The value of passing references through untrusted 
intermediaries is also unclear.

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