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

["marcelo bagnulo" <mbagnulo@ing.uc3m.es>]

> 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.

Ok, as it is stated in Christian's draft, this will definitely be the case
for some sites for it is also certain that for other smaller sites this will
not be the case.

>
> > 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.
>

Well, IMHO source address based routing is a good option for small sites (at
least).
you can easily implment it is this case, since you can use currenlty
available Policy based routing mannually configurated in the (few) routers
on the site.
For larger sites, this *may* be more difficult, and it also presents
additinal difficulties, such as the fact that policing is performed by the
hosts (which is seen as a problem by some site admins) (BTW the same admins
have claimed that multiaddressing is a problem for them too)

So we are again in the situation where one size fits all solution seems more
difficult than a per case situation.
Some people have expressed that big sites will continue doing multihoming as
they do now in IPv4 and that that is ok.
Do you think that we should look for different solutions depending on the
characteristics of the site?
and,do you think that for small sites source address based routing seems to
make sense?

Regards, marcelo

>   Erik
>
>