Re: [RRG] Idea for shooting down

[Scott Brim <swb@employees.org>]

Excerpts from Brian E Carpenter on Fri, Nov 23, 2007 09:59:59AM +1300:
> On 2007-11-23 01:13, Iljitsch van Beijnum wrote:
>> On 19 nov 2007, at 22:59, Brian E Carpenter wrote:
>>> http://www.cs.auckland.ac.nz/~brian/DFZng.pdf
>> I don't understand how this works... Would ISPs at each level aggregate 
>> the address prefixes used at the level below, or would addressing be 
>> completely separate from the hierarchy so some kind of 
>> mapping/encapsulation would need to happen?
>
> The second case. There would not only be a separate instantiation of
> BGP4 in each region, but also a separate instantiation of (e.g.)
> LISP-ALT. The idea is to recurse the whole model (EGP and locator-locator
> mapping). ((Er, LISP EIDs are a special case of locator as far as
> I'm concerned.))

Brian, I believe the goal is to reduce the number of map entries that
an ETR might want to cache.  However, the lookup key for a cache entry
is the ultimate prefix.  Reducing the number of ETRs doesn't help.  If
I understand your scheme, reducing the number of entries depends on
prefixes being more aggregatable as you bring in your higher levels of
ETRs.  There will certainly be some aggregation if "regional" IRs
continue to allocate address blocks, but there will always be
outliers, for example when a USA oil company relocates to Kazakhstan.
So your scheme helps if address allocation is constrained to follow
topology ... but if that's true then the problem I think you solve
doesn't arise.

So based on what you say above, I no longer think I understand what
problem you solve.


Excerpts from Iljitsch van Beijnum on Sat, Nov 24, 2007 10:47:50PM +0100:
> Since you ask: what I would like to see is a combination of something from 
> the LISP family combined with a hierarchical mechanism like CRIO that 
> allows packets for which there is no mapping yet to be delivered through 
> increased stretch.

Take a look at the LISP interworking draft.
http://www.1-4-5.net/~dmm/draft-lewis-lisp-interworking-00.txt

Does that do what you want?

CRIO had "destination-side" default routers (my terminology), serving
particular destination prefixes on behalf of all sources.  The other
model is to be more "source-side", serving all destinations on behalf
of a particular set of sources.  An intermediary like you want can be
either, depending on deployment optimizations.  The LISP interworking
draft calls them proxy tunnel routers.

swb

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