Re: [RRG] On the Transitionability of LISP

["Mark Handley" <M.Handley@cs.ucl.ac.uk>]

On 8/2/07, Robert Raszuk <raszuk@juniper.net> wrote:
> David,
>
> But what would be the trigger ? What makes a critical mass that anyone
> could stop advertising their addresses into DFZ ?

It seems to me that the problem is basically disaggregation, which is
reasonably closely related to multihoming.

One scenario is that LISP-enabled sites actually get proper
multihoming (so long as both ends are enabled), but non-LISP sites
increasingly find that their long-prefix routes are filtered by ISPs
that buy into LISP.  It's not that non-LISP sites are unreachable;
it's just that they're only reachable via the aggregated path, and
their multihoming doesn't work the way they wish.

A possible early stage of such a transition plan might involve LISP
sites continuing to advertise their existing long prefixes for their
multi-homed customers, but marking them with a transitive attribute
that says "you may drop this route if you do LISP".  Thus LISP-enabled
networks have smaller routing tables than non-LISP networks.  After
enough LISP sites exist, they can also start filtering routes with
long prefixes that are not marked in this way.

Anyway, it's premature to fixate on the details of this at this stage;
the point is that there are transition paths that don't involve making
prefixes unreachable but rather make then suboptimally reachable.

 - Mark

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