[Ecrit] Consensus Call: Precise Location Information not available to End Host

[Hannes Tschofenig <Hannes.Tschofenig at gmx.net>]

Hi all, 

let me try it again (I got it wrong in my previous mail). 

Henning and Brian suggested an approach that 
* works nicely with the emergency services architecture we
investigated over the past few years, and
* addresses the case where a network operator 
does not want to disclose precise location information. 

Here is the procedure:

1. The endpoint uses an LCP to request location.  The LIS returns an LbyR
2. The endpoint dereferences the LbyR.  
3. The LIS, noticing that the dereference request is from the endpoint (or
at least not from any entity that is entitled to get fine grained location),
takes the fine grained location and uses LoST to determine the PSAP that
serves that location.
4. The LIS returns to the endpoint a location which, if submitted to LoST,
would return the same PSAP URI the fine grained location would.  In some
circumstances, this could be a civic with only a country.  An alternative
that works for all circumstances is to return the polygon that defines the
service boundary of the PSAP (which LoST can return).  Is essential that the
PSAP URI returned from a LoST query with whatever the LIS gives the endpoint
would be the same PSAP URI any querier using the fine grained location would
get.
5. The endpoint uses the (coarse) location value it obtains to query LoST.
It gets the (correct) PSAP URI
6. This is repeated at call time.  The endpoint has a valid LbyR and a valid
PSAP URI, which it uses to construct the emergency call
7. A VSP wishing to validate the PSAP URI takes the LbyR and dereferences
it.  The result will be the same (coarse) location the endpoint got.  The
VSP does a LoST query with that location, and should get the same PSAP URI
that is in the Request URI on the call.  This validation works for coarse or
fine validation, and of course works for LbyV without the dereference step.
8. The PSAP (or ESRP) which is the target of the PSAP URI gets the call.  It
dereferences the LbyR but gets the fine grained location; the LIS must have
a relationship with the ESRP/PSAP to assure this.
9. Any succeeding ESRPs or PSAPs can also dereference and get fine grained
location.

QUESTION: Is this approach acceptable for you? 

Ciao
Hannes



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