Subject: (IPng 7017) Re: route distribution via ND

From: Richard Draves <[email-masked]>
Date: Wed, 6 Jan 1999 13:58:15 -0800

> I think that is the only way to build a robust network.
> Having "half-routers" that forward some packets but drop other packets
> on the floor will, when something goes wrong, cause black 
> holes that are
> very hard to find.

Yes, I agree with this.

> > Btw, I think multi-homed hosts are a very important case - 
> a host with a
> > single physical interface can also have virtual interfaces,
> 
> The multihomed case where you need more information for 
> optimal routing
> is when a host has multiple *physical* interfaces (so that 
> the node can
> select the outgoing interface). Virtual interfaces doesn't
> add any new requirements here as far as I know.

I don't see the difference between physical interfaces & virtual interfaces.
(By definition :-). For example a multi-homed host with a physical ethernet
interface and a virtual 6-over-4 interface is faced with the same problems
as a multi-homed hosts with two physical ethernet interfaces.

> If we go this path I fear we will soon be getting requests 
> for being able
> to authenticate the content of this routing option (but not 
> using AH for
> the whole packet) since RIPng has such support. Thus I fear 
> we will end up
> with a discussion of what parts of RIP to move into ND and 
> that we might
> end up with most of RIPng functionality in ND. What for?

I think pretty much all the other information in RAs would want the same
security/authentication as routes. RAs are already used to communicate
information about default routes and "on-link" routes. This information
should be authenticated. Information used for address auto-configuration
should be authenticated. Etc.

So in fact it would seem simpler to me to have a single system to
authenticate RAs, then to authenticate RAs and RIPng separately.

Rich
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From: Erik Nordmark <[email-masked]>
Date: Wed, 6 Jan 1999 15:26:44 -0800 (PST)

> as a multi-homed hosts with two physical ethernet interfaces.

Correct (at least in principle).
I didn't understand what you meant by "virtual".
What I was trying to point out that that while the definition for
multihomed is >1 IPv6 address it is really the number of interfaces
that creates an issue.

But in your specific case (an ethernet and a 6-over-4 interface) it would make
most sense to only use one of those at a time.
One way of implementing this would be:
	When the host finds a default router on the ethernet it would 
	effectively turn off (or at least stop transmitting on) the 6-over-4
	interface.
	When there are no default routers on the ethernet (or no non-link-local 
	addresses assigned to the ethernet interface) it would switch back
	to transmitting on the 6-over-4 interface.
	[I personally think preferring the ethernet over 6-over-4 since it
	avoids encapsulating overhead as well as reduces IPv4 multicast
	traffic.]

> authenticate RAs, then to authenticate RAs and RIPng separately.

I spoke without checking RIPng. RIPng uses IPsec for authentication
thus there won't be any pressure to add any RIPng specific authentication
to your proposed new ND option. (But key distribution and authorization
checks will be hard problems for anybody building ND/RIPng security.)

But that doesn't change my basic argument: there will be pressure to
ensure that your new ND option has all the features and capabilities
of RIPng. Why invent a new packet/option format when RIPng can be used
for this today?

   Erik