Re: Alternatives to source address rewriting (was RE: Preserving established communications (was RE: about draft-nordmark-multi6-noid-00)

[Erik Nordmark <Erik.Nordmark@sun.com>]

> So, backward compatibility with non M6 enabled host require a alternative
> mechanism to source address rewriting. ULP hints would also require it. And
> packets exchanged before context establishement would also benefit from it.
> The identified mechanisms to provide this would be source address routing or
> a routing header.
> Do you agree with this summary?

Another possible solution in some scenarios is that the ISP's ingress filtering
is relaxed to allow all the prefixes assigned to the site. That might not be
realistic for the low-end services for home users, but it might be a useful
approach in other cases.

> The question here is whether every multi-homed ISP will be able to get an
> allocation or it will have to obtain addresses form its upstream providers,
> right?
> 
> Well let's assume that it will obtain addresses from their upstream
> provider.
> Let's asume that ingress filtering will be in place, ok?
> 
> Now, how would you deal with this without source address based routing?

Not doing strict RPF ingress filtering between the ISPs seem to be the
current operational approach for such problems.

My gut feel currently is that one would need a really strong case
to make the routing system operate on source and destination addresses.
I've yet to see such a strong case.

But perhaps tweaking the routing system to do so is downright trivial
and I should sit down and shut up.

  Erik