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>]

> > But the host will never know better than the routing system because it
> > is operating on aggregated information.
> 
> Don't understand this...
> The routing system is the one who works with aggregated information implying
> information loss.
> The host deals with no aggregated host information

I guess my statement wasn't very clear.
While the host has some information about reachability of src/dst locator
pairs, it does not have information on how this maps to the exit paths from
the site. For instance, if the host could choose between 3 destination
locators it wouldn't know that for instance the first two result in the same
exit path being used.
That level of information is known in the routing system.

> We still have to provide some way to provide
> ingress filtering compatibility for non M6 capable communications. The
> benefit of source address based routing is that it also addresses both
> situations (or kind of)

I'm upleveling this part of the discussion a bit.

I think the goal should be a workable and deployable multihoming solution.
Whether that also provides incremental benefits for steps along the way
(such as current ingress filtering issues for sites that have multiple prefixes
and multiple ISPs) doesn't look like the highest priority to me; if that bogs
us down so that we can't come up with a multihoming solution then I think we
need to ignore it. If we don't have that attitude we might become so entangled
by incrementalism that we can never design the necessary multihoming solution.

  Erik