Re: [lisp] Comments on draft-fuller-lisp-alt-04

[Scott Brim <[e-mail]>]

Excerpts from Vince Fuller on Wed, Feb 18, 2009 11:18:16AM -0800:
> In a separate discussion, Dino pointed-out that an ALT router may be
> running vanilla BGP and GRE with no knowledge at all of LISP. This
> may, in fact, be the common case. If so, then the ALT router will
> not know anything about the Map-Request - it will only know that the
> destination IP address (the EID) is unreachable and will simply drop
> the packet. Not clear whether it should even return an ICMP
> unreachable.

How would you make the distinction between a prefix that is
operational but not reachable, and one that just isn't operational?
Are you going to configure all intermediate ALT routers with all of
the allocated prefixes?  How is it going to know which ones are not
just allocated but operational?  Not only that, but suppose a
high-in-the-hierarchy ALT router loses all routes to a next-longer
prefix, even though that next-longer prefix is an aggregate?  How is
it going to know if all of that prefix is supposed to be operational?
This is a lot of configuration.  I think you're better off not trying
to be too smart here, and if there truly isn't a route on the ALT,
just drop the Map-Request