North American Network Operators Group

Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

Re: How relable does the Internet need to be? (Was: Re: ConvergedNetwork Threat)

  • From: Paul Jakma
  • Date: Sat Feb 28 21:56:15 2004

On Fri, 27 Feb 2004, Alex Bligh wrote:

> Anycast topology tends to follow AS topology, as people prefer
> their own routes.

Indeed yes.

> routes. If you take a rural situation where you have your nearest
> (geographically) E911 service on some long link into Sprint, and
> the customer on some long link into UUnet, it is most unlikely they
> will be close (network wise)


But who said anything about having anycast addresses routed /that/ 
widely? The anycast address can simply be the well-known 'emergency 
service' address. It can then be up to each service provider to route 
calls from customers to the appropriate emergency service provider.

Eg, in your example above, if we decide we do not want to put the
onus on customers to configure their 911 service, then UUNet are in
the best position, indeed noone else is in a better position, to know
that $long-haul-customer is located in Ruralville, so UUNet's E911
'switch' would need to have a table of (customer or POP) ->
(appropriate emergency service provider). UUNet can deploy as many or
as few of these switches/gateways as they want.

Ie, anycast == well-known-address, every VoIP phone could be
pre-configured with it even. From users POV, it'd just work presuming
the network provider does the needed work. Even for mobile users.

And even if they dont, it would still allow for the provision of
public emergency service switches/gateways as a fallback which have
some chance of being on the same continent, occasionally even the
same country, where a 'best guess' could be made (eg by looking to
see whether the inetnum for the source has a country: attribute or by
some other IP->locality mapping technology).

This presumes SIP has the facilities to support the needed

> Anycast is arguable good for finding the best *connected* (i.e.
> closest using a network metric) server, 

Indeed, however you are presuming the servers are far and few
between. It need not be.

> need to. For E911, it does.

Yes of course. Difficult problem though. And the best place to decide
is as close to the person making the call as possible.

> Alex

Paul Jakma	[email protected]	[email protected]	Key ID: 64A2FF6A
	warning: do not ever send email to [email protected]
Use what talents you possess: the woods would be very silent if no birds
sang there except those that sang best.
		-- Henry Van Dyke