Subject: Re: [Ecrit] Emergency Context Routing of Internet Technologies-Architecture Considerations

From: "Stastny Richard" <[email-masked]>
Date: Wed, 7 Sep 2005 09:54:43 +0200

>[AJW]
>I think that this approach is at odds with NENA, which does not want
>every Tom, Dick and Harry having the ultimate address of the PSAP. I
>tend to agree with the NENA approach. It may be prudent to provide the
>address of the ESRP, but an ESRP is likely to service a number of PSAPs.
>This gives the flexibility within the emergency services network to
>determine how internal routing is performed, without revealing its
>internals to the rest of the world.

Both approaches are valid and need to be supported. Basically
it is a matter of the local authorities where the SIP URI for
a given location points to. The ESRP is needed especially
in the migration scenarios where you may point a whole country
to one ESRP and do the whole mapping behind the scenes
e.g. routing to an ESGW to access TDM PSAPs.

I also cannot fully see the argument to provide Toms and Harrys
not with the ultimate PSAP address, but the address of the ESRP
instead. It is a single point of failure and may also be the easy focus
of DoS attacks. This problem has to be solved anyway.

-richard

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From: Andrew Newton <[email-masked]>
Date: Wed, 7 Sep 2005 08:02:06 -0400

> of DoS attacks. This problem has to be solved anyway.

I agree with Richard on this.  But I sense a recurring meta-issue  
here.  Just how much information is to be considered publicly  
visible?  Such as the PSAP URIs or the polygons of the PSAP coverage  
area...

-andy

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From: "Brian Rosen" <[email-masked]>
Date: Wed, 7 Sep 2005 10:51:26 -0400

There is a piece of mythology at work here.
There are VENDORS who believe that service boundaries of PSAPs are secret.
There are VENDORS who believe that URIs of PSAPs are secret
NENA has no position, to my knowledge, on this issue.

I have asked, repeatedly, for any PSAPs who have such beliefs to please let
me know.  So far, no PSAPs have stepped up.  From that I conclude that it's
a myth, possibly a self serving myth, to claim that PSAPs believe service
boundaries or URIs of PSAPs ought to be secret.  

PSAPs do have legitimate concerns about denial of service, and they want to
understand the issues associated with widely publishing their URI, in the
same sense anyone with an email address worries about their address being
widely known.

ESRPs are useful in this regard, as they provide a boundary where defenses
may be mounted with more expertise than the average PSAP can muster.  I do
think however, that [email-masked] is a perfectly reasonable
URI to get out of the mapping function.  The domain, psap.state.pa.us, could
provide an ESRP adequately protected, while the fact that the Pittsburgh
PSAP is the ultimate destination is plain for all to see.  There is a
certain balance between making routing of emergency calls simple enough that
it works when great parts of infrastructure die, and making it trivial to
DoS attack a PSAP.  I'm not sure I want to make the URI
[email-masked], because I really do worry about the
ability of that domain to protect itself adequately.

Brian

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of
Andrew Newton
Sent: Wednesday, September 07, 2005 8:02 AM
To: Stastny Richard; ECRIT
Subject: Re: [Ecrit] Emergency Context Routing of
InternetTechnologies-Architecture Considerations

-andy