Re: [RRG] Consequences of no renumbering...

[Scott Brim <swb@employees.org>]

Excerpts from Noel Chiappa on Thu, Sep 11, 2008 09:14:22AM -0400:
> For instance, although I looked at both having only a single routing
> plane, in which 'locators' and 'addresses' mixed (which seems to be
> the assumption in some of what you're saying), I spent more time
> thinking about systems with two separate routing planes (one for
> each), and where _not all routers participated in both planes_
> (exactly because, as you point out, otherwise "there wouldn't be any
> reduction in prefix count [in any router] until transition was
> wholly complete"), examining such issues as 'where, and how, would
> routes from one need to be injected into the other'.

Just in response to the basic concepts ...

First I don't think there is ever more than one routing plane.  I
think the conceptual key is asymmetry in scope.  As things are now,
routing/forwarding scope is global.  As a site splits off and adopts
map-n-encap, the rest of the Internet is removed from its
routing/forwarding scope, so that in order for a packet to be
forwarded to it a new adaptation mechanism (map-n-encap) must be
invoked ... but everything in the global Internet is still directly
reachable by it.  The scope of the site is narrowed to just the site,
while the scope of the global Internet remains global, including the
site.  

These are not two routing planes.  At the adaptation points (xTRs)
there is a new routing mechanism to allow adapation between different
routing/forwarding *scopes*, but only one routing plane and only one
routing mechanism.  BGP is also used for discovering mapping
authorities in LISP+ALT, but that's a completely different use of a
routing protocol -- it's in support of the Internet's control plane
(mapping), not the Internet's data plane.

Scott

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