Re: [Geopriv] Location-by-value in a SIP Location Header

>> The use case is proxy-inserted location, where the proxy does not have 
                    ^^^^^^^^^^^^^^

I'm assuming that the proxy knows whether it has access to a web server 
or not. The UA really wouldn't know or care in that case.

> ok, but how would a UA know it's behind a corporate NAT/FW, instead of 
> at a home using the SP's LIS beyond the NAT/FW, to know to use a data 
> URL instead of by-value or by-reference PIDF-LO?

I would expect a UA to always use by-attachment unless it used an L7 
location mechanism that provided a reference to an object on a LIS 
somewhere. (This, by the way, raises some additional issues; how can the 
  UA know that the pointer it got from the LIS is accessible, by policy, 
to a random third party?)


> We're talking about all SIP elements that understand this extension now, 
> if we do as you and Hannes are suggesting, include a third 
> representation.  That's more code for every UA to include, and every 
> location aware SIP server.

I generally share concerns about code complexity, but we're talking 
pretty trivial code here. In a PHP-like language, it would be something like

if (url['scheme'] == 'http') {
   $fd = fopen($url);
   $lo = fread($fd);
} elseif (url['scheme'] == 'data') {
   $u = split(',', $url);
   $lo = base64_decode($u[1]);
}

Only the last elseif is data-specific. In other words, not exactly a big 
deal.

> 
> I hear your arguments below essentialling meaning location by-reference 
> is a woefully underspecified user-case, and that it is the one that 
> ought to be the one that may be dropped from the list within this 
> extension proposal (because there is not enough there).  Are you going 
> down that path here?

There may well be deployments where by-reference is valuable (such as 
where the LIS already provides by-reference location information to the 
proxy), but I fear that if we only do S/MIME attachments, the practical 
outcome is going to be lots of SBCs modifying SIP bodies.


> should by-reference be taken out as an incomplete piece to an 
> underspecified solution, IYO?

I believe it is currently underspecified; I won't go as far as 
suggesting it be taken out as noted above.


> 
> 
>> Henning

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