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Re: Looking for BGP resource utilization information...
From: "Richard A. Steenbergen" <ras () e-gerbil net>
Date: Mon, 7 May 2001 13:57:53 -0400 (EDT)


On Mon, May 07, 2001 at 10:45:18AM -0400, Thomas Gainer wrote:

Does anyone know of any good papers that explain memory resource
utilization during the BGP table construction.

Post Note:  Yes, I have read the RFC.  I am looking for additional
resources.

For traditional implementations of BGP. as described by the rfc (btw the
rfc is pretty loaded with mistakes, draft-ietf-idr-bgp4-12 is a bit better
though not perfect itself), I think the word you're looking for is "lots".

Memory requirements will theoretically differ quite a bit between
implementations, and depending on the routes you receive. For example
every half-decent implementation I'm aware of uses an attriute hash to
reduce memory requirements where multiple prefixes share common
attributes. But if you receive routes with all unique attributes (for
example by randomizing the med value or somesuch), you'd burn through
memory a LOT quicker than normal (sh ip bgp sum and see where your memory
is going :P). Traditional RIBs using patricia trees are also quite bad for
BGP, in addition to burning memory they they are extremely inefficient for
the actual BGP usage of insertions and deletions with a known prefix
length. I'd say that 95% of the fault of slow converging and memory
sucking BGP can rest squarely on the shoulders of bad implementations.

If there are any papers on BGP memory usage and performance of the actual
algorithms used, I'd love to see one. I did a quick check on citeseer and
didn't turn up much of interest.

The only things notable were the following, still not very useful:
http://citeseer.nj.nec.com/422681.html
http://citeseer.nj.nec.com/333036.html

-- 
Richard A Steenbergen <ras () e-gerbil net>       http://www.e-gerbil.net/ras
PGP Key ID: 0x138EA177  (67 29 D7 BC E8 18 3E DA  B2 46 B3 D8 14 36 FE B6)



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