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

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

On 3 nov 2003, at 17:50, Erik Nordmark wrote:

> > Another way to handle this would be to bascially build two networks 
> > all
> > the way down to the host:

> > ISP A     ISP B
> >     |        |
> > Router    Router
> >     |        |
> > Router    Router
> >       \   /
> >       Host

> > So the ISP selection happens inside the host, once a network is
> > selected it is no longer possible to deviate from the path intended by
> > the host.

> Isn't that what source address based routing implies conceptually?

I suppose. But the important thing here is that only the host needs to 
have the SABR capability, in this picture the routers must do it:

ISP A   ISP B
   |      |
Router  Router
    \    /
    Router
       |
     Host

> It can be implemented while sharing the routers as long as the routing
> table has the entries learned from ISPA as tagged to only apply to 
> packets
> with a source address from A's prefix and vice versa.

In essence we'd be doing type of service routing here, but rather than 
use different types of service we use different source prefixes. But as 
discussed before, simply bypassing normal routing and forward based on 
the source prefix exclusively is simpler.