Subject: [Ecrit] Re: [Geopriv] RE: Strawman Proposal

From: Henning Schulzrinne <[email-masked]>
Date: Wed, 14 Mar 2007 08:44:28 -0400

>
> My point, however, is that the actual identity of the caller isn't the
> gating factor. Indeed, the question of whether you're using your phone
> or someone else's doesn't come up.

The whole point of disallowing SIMless emergency calls is that

- it makes it impossible to find and fine the nuisance caller

- the caller knows that and acts accordingly

I believe that traceable identity largely addresses the individual  
nuisance call problem. (Unlike for SIMless phones, where the SIM is  
tied to having a contract and paying, it is much easier to imagine no- 
fee, verified SIP accounts that only do emergency calling.)

Just like location signing, this does not have to be perfect to be  
useful. Most everyone seems to agree that not all calls will have  
signed locations, so, with any assurance scheme, PSAPs will have to  
deal with unauthenticated and unsigned calls, using the  
prioritization mechanisms Brian keeps talking about.

The advantage of verified identity is that it works today, without a  
new infrastructure or a new national CA. Thus, I see it as an  
important part of the tool kit that will lower the deployment hurdles  
and will allow us to avoid having to build a perfect location signing  
system.

Thus, I can imagine four levels of calls:

(1) assured identity and assured fine-grained location

(2) assured identity and unsigned location -> unlikely to be spoofed;  
equivalent to a large fraction of today's wireless calls

(3) no traceable identity and signed location -> equivalent to a  
payphone or SIMless wireless call today, i.e., treat with caution

(4) no identity assurance, no location signing -> suspicious, handle  
with care and drop during overload

Here, identity can be either a L2/L3 identity or a VSP identity; it  
really doesn't much matter, although VSP identity is the one that's  
currently available without extra mechanism.

The "bot net" out of area attack vector is a different issue and  
should be discussed separately.

Henning

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