[c-nsp] BGP table growth and memory

[Rick Ernst]

On Mon, 20 Jun 2005, Tony Li wrote:

:>Rick,
:>
:>> I've watched the BGP table increase by about 30K entries over the last
:>> year, and memory on a 7206 drop by about 20MB, with about 40MB still
:>> available.
:>>
:>> Is there any way of estimating base/operating memory requirements based on
:>> table size, number of peers, etc?  Is 256MB only OK "for another 2-3
:>> years", or am I turning myself into Chicken Little?
:>
:>What you're really asking is how fast the BGP table will increase.

Actually, I've got what I think is a reasonable expectation of what the
growth will be (it looks roughly linear for the last couple of years, with
a slight exponential charactistic).

:>>From the data that you already have, yes your guess seems about right,
:>and given that your situation (set of peers, multipath links, filtering,
:>etc.) is unique, it's probably the best estimate that anyone can give you.
:>
:>If you're looking for a definitive answer, you might consider getting a
:>tarot reading.  ;-)

I'm looking for a a rule-of-thumb (or better :) as to what the correlation
is between table size (both number of entries, and AS-path length), and
memory consumption.  "20MB per 30K routes" is what I've seen over the last
year, but I don't know how many other variables make an impact on that.

But, yes, my real question is when should I start worrying about table
growth.  I'm "concerned" right now, and my somewhat educated guess is 2-3
years before we hit critical mass, but I'd rather be conservative than
optimistic in my planning, since once the tipping point is reached it's
going to be a real mess.

I'm surely not the first person to notice this, so I have to wonder what
kind of plans/forecast other small/medium providers have, other than a
forklift upgrade.

Rick


:>Tony