Subject: Re: Host-based may be the way to go, but network controls are neccessary

From: "J. Noel Chiappa" <[email-masked]>
Date: Thu, 21 Nov 2002 23:11:42 -0500

> From: Iljitsch van Beijnum <[email-masked]>

    > CIDR was a very good thing to do as we are essentially now solving
    > this problem 10 years later so it bought us 10 years.

Huh? CIDR was principally supposed to stop routing-table explosion caused by
uni-homed sites, which it did quite well. It was never intended as a
solution to multi-homing, for the simple reason that it's no use there.

    > However, it does chip away at the underlying IP architecture.

Sorry? I didn't follow that, at all. Can you explain the reasoning?

	Noel

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From: Iljitsch van Beijnum <[email-masked]>
Date: Fri, 22 Nov 2002 15:47:11 +0100 (CET)

> solution to multi-homing, for the simple reason that it's no use there.

Routing table explosion is routing table explosion... But you are right
these aren't really the same as they are caused by different needs.

> Sorry? I didn't follow that, at all. Can you explain the reasoning?

Build a network using an assumption. Break the assumption. Repeat.

It used to be that if something was in the routing table, it was
reachable. Today, if there is an aggregate in the routing table, the
aggregated (sub)networks had better be reachable. If we do
locator/identifer seperation, being reachable is still a good idea but
if a set of locators isn't: too bad. We don't flood this information
throughout the network and we also don't have to repair it using
backdoor routes or tunnels. So routing becomes much less dynamic.

Signing off now, the IETF55 wlan can't be around for much longer...

Iljitsch

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From: RJ Atkinson <[email-masked]>
Date: Fri, 22 Nov 2002 13:13:10 -0500

On Friday, Nov 22, 2002, at 09:47 America/Montreal, Iljitsch van 
Beijnum wrote:
> If we do

Given that there is no specific proposal for locator/identifier
separation, the above it totally bogus.  Routing is no less dynamic
than at present.  Somehow the concept must be unclear, so I'll try
to explain a bit.

It is better to think about the separation this way:
	Currently we overload the "address" with both "identity of end system
	(or its interface)" and "location in the topology".   The proposal
	removes that overloading.  The "routing system" continues to propagate
	the location information (i.e. topology).  However, a host can move
	around the topology without being forced to change its identity.
	And there clearly will need to be an identity-->location mapping 
scheme,
	for which the existing DNS system is an existence proof that such
	name to location mappings are feasible to implement and deploy.

	In one sense, Mobile IPv6 is already doing all this.  Consider that the
	"Home Address" is functionally the identifier and the "Mobile Address"
	is functionally the locator of a mobile node in a Mobile IPv6 
deployment.

So the proposal to separate the two concepts and remove overloading is
neither new (e.g. Nimrod, Mobile IPv6), nor impossible to implement
(e.g. DNS FQDN-->IPaddr translation, Mobile IPv6's new Destination 
Option
carrying the identity).

A useful new property of such a schema is that mobility of nodes becomes
a first-order property of network, not a step-child.

Ran

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From: Kurt Erik Lindqvist <[email-masked]>
Date: Sat, 23 Nov 2002 19:55:04 +0100

> backdoor routes or tunnels. So routing becomes much less dynamic.

I am not really following this. There is not functional difference 
between having an aggregate route point to a "IGP more specific view" 
and generate a no route to host or if the route is missing from the DFZ 
and then generating a no route to host.

- kurtis -