Re: [Ecrit] Solution Approaches

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

Hi Henning,

Henning Schulzrinne wrote:
> > 2) Provide LbyR + Dial String + PSAP URI to the end host.
> > We could ignore the potential security vulnerabilities if charging 
> > does not work on a call-by-call basis.
> >
> > CONSEQUENCE: No changes needed.
>
> We still would need to define how the UA acquires the dial string and 
> PSAP URI.
Right. I forgot that part.

> Using LoST would require a change to LoST (resolving LbyR) and a 
> business relationship between the LoST server and the ISP (as well as 
> a way to discover the LoST server that can resolve the LbyR).
>
> The alternative is to provide the country code (via LCP/DHCP/...) to 
> the UA and have the dial string be looked up via LoST, with the PSAP 
> configured via SIP configuration.
>
> Thus, whichever way it's done, this requires additional protocol work.
Correct.

> > 3) Provide LbyR + Dial String + PSAP URI to the end host. VSP does a 
> > reverse LoST lookup to verify the PSAP URI.
> >
> > CONSEQUENCE: Solution needs to be developed.
>
> This seems to be the same as #2.
No. Item (2) just assumes that we ignore the security vulnerability 
(fraud) because we believe it is not a real problem.
For item (3) we believe it is a problem and provide a solution to it.

> > 4) Provide LbyR + Dial String + PSAP URI to the end host. VSP 
> > verifies the PSAP URI with the PSAP URIs being flooded (using the 
> > LoST synchronization mechanism). This mechanism is potentially 
> > similar to (3) -- details might vary. (3) might use a distributed 
> > approach whereas this is brute force.
> >
> > CONSEQUENCE: Solution needs to be developed.
>
> Again, I'd like to separate the verify-URL-is-PSAP problem from the 
> location problem. These are completely separate issues, as the 
> verification problem only affects the VSP, as it charges for calls.
There are many aspects that play an important role for the solution:
* location
* verification
* authentication
* deployment considerations
* callback aspects

All these issues have to be considered and cannot be treated 
independently. For some of the solutions we solve the PSAP URI 
verification with call routing through a SIP proxy in the access. This 
also addresses the location aspect.


Ciao
Hannes

> Henning


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