Re: [RRG] Opportunistic Topological Aggregation in the RIB->FIB Calculation?

["K. Sriram" <ksriram@nist.gov>]

At 02:32 PM 7/22/2008, William Herrin wrote:
> I haven't crunched any numbers but my guesstimate is that towards the
> edge you'd get compression down to a few thousand FIB entries while
> deep in the core you'd get 25% to 50% compression and in the worst
> case you'd get 1/X compression where X is the number of BGP interfaces
> on the router.

Bill:

X can be quite large for core BGP routers -- 100s of peers or BGP interfaces.
In that case, the worst case of 1/X would be negligible compression.
Do you have some data available regarding distribution of prefixes
that exit using the same BGP interface? Just looking for some
empirical support for your guesstimate of 25% to 50% compression
in the core.

The other fundamental question would be: Even if it 25% compression,
given that the total number of FIB entries are projected to increase
four fold over what we have today (from ~250K to ~1 million or so),
we would still be seeing an increase (post 25% compression)
from ~188K to ~750K (assuming that the FIB increases are proportional
for all BGP interfaces or exits).

Sriram

K. Sriram, Ph.D.
National Institute of Standards and Technology
Web:  http://www.antd.nist.gov/~ksriram/



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