Re: draft-ietf-multi6-multihoming-requirements-03

[Iljitsch van Beijnum <iljitsch@muada.com>]

On Tue, 2 Jul 2002, Joe Abley wrote:

> > Ok, nothing wrong with that. But BGP doesn't provide any functionality
> > to really help with this.

> Well, BGP plus CIDR abuse does. If I operate 203.97.0.0/17, and I obtain
> transit from two providers as vaguely described, I can hang all my
> satellite-tolerant gear in (say) 203.97.2.0/24 and advertise just
> 203.97.2.0/24 over the satellite circuit.

And you must also make sure the servers you communicate with are routed
over the satellite link. If you don't, you'll have to use policy routing.

> The fact that I am able to
> advertise covered routes to make things work is central to the way that
> multi-homing is made to work with v4, and is one example of things we
> are trying to provide core-safe alternatives for in v6.

Basically you are using two different address ranges here, one multihomed
and one single homed. (The fact that they overlap in this particular
instance is not important.) This is such a basic capability that I can't
even imagine a multihoming solution that conflicts with it.

> >  Since it can be done now without help from BGP,
> > there is no reason an IPv6 solution should specifically cater to this
> > need. Just not getting in the way of more specific routes or policy
> > routing should be enough.

> It seems feasible to me that there will be solutions to the requirement
> as currently stated on the draft that do not need to rely on policy
> routing or the advertisement of covered routes. I do not have such a
> solution in mind, but I don't see why we should discount the possiblity
> that one might exist.

Making scalable multihoming work is difficult enough without overloading
it with extra nice to have features. But since I think this functionality
can be provided regardless of the multihoming solution, and there is
little harm in looking to optimize things, I'm not going to object very
strongly.

> > "Existing IPv4 multihoming practices can coexist with policy-based
> > routing
> > and forwarding mechanisms. An IPv6 multihoming architecture should
> > retain this capability."

> As I said, I think that presupposes a solution.

I didn't have one in mind when I wrote it.