Subject: Re: [RPSEC] Definition of Routing Protocol - Routing System

From: Radia Perlman - Boston Center for Networking <[email-masked]>
Date: Fri, 15 Nov 2002 15:56:36 -0500 (EST)

Re: Russ's note, below

It's not so intractable. That's what my thesis did..how to get
the data there even if routers are being really obnoxious.
It was fairly straightforward to do with link state routing,
and source specified routing (at least as a backup if the "default"
computed route doesn't work for you). But without that, I couldn't
figure out how to do it (which doesn't mean it can't be done of course :-)  )

Radia
	
	The problem is that routing is a hop by hop affair.... Just
	because you've secured the generation of a routing table doesn't
	mean you've secured the forwarding of the packet. If we are to go
	further than being able to verify/validate the routing
	information, and into validating the forwarding information, and
	forwarding behaviour, of each device in a network, the problem
	becomes much more complex, and, I would argue, outside the pervue
	of the routing group at all, most likely.
	
	You would then be delaing with how to secure the devices
	themselves against having false routing information manually
	installed on them, for instance, and how to prevent the
	forwarding table from being attacked through icmp redirects,
	etc. This, then, would take us into the territory of passwords on
	devices, etc.
	
	Do we really want to go there?
	
	:-)
	
	Russ

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From: Iljitsch van Beijnum <[email-masked]>
Date: Fri, 15 Nov 2002 23:40:11 +0100 (CET)

> figure out how to do it (which doesn't mean it can't be done of course :-)  )

As a BGP consultant, this is (part of) what I do for a living. Traffic
flows over a path that has an undesirable property. For instance, two
large ASes in the middle find it easier to peer on another continent.
For outgoing traffic, this is fairly easy to fix by lowering the
preference for a route if a certain combination of ASes shows up in the
path. For incoming traffic, this is harder. Fortunately, many of the
larger transit networks give their customers the option of influencing
how their routes are announced further upstream using BGP communities.

It would be better if there was a protocol to do this automatically,
though...

Iljitsch