Mailing List Archive: Quagga: Dev

Large Prefix-list Performance on Quagga

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dietmarhmann at gmail

Jul 25, 2012, 1:06 AM

Post #1 of 3 (255 views)
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Large Prefix-list Performance on Quagga

I have an old router which I don't want to upgrade right now.

To optimize my BGP connection to my provider, I installed a long
prefix-list (around 2K) and accept default-route on all other routes from
provider.

However, to my surprise, now peering establishment nearly takes 3 times
more time than ever (80sec vs 29sec) for exchanging 0.1% of previous table
(600 vs 390K). To me it is inefficient, spending more time on exchanging a
miniscule subset of prefixes although there must be some cost of
introducing filters.

I am wondering if this is related to Quagga or a common thing.

There is an outdated NANOG reference on prefix-filter performance myths but
I assume things must have improved since then.

nick at inex

Jul 25, 2012, 1:26 AM

Post #2 of 3 (239 views)
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Re: Large Prefix-list Performance on Quagga [In reply to]

On 25/07/2012 09:06, Dietmar Hartmann wrote:
> However, to my surprise, now peering establishment nearly takes 3 times
> more time than ever (80sec vs 29sec) for exchanging 0.1% of previous table
> (600 vs 390K). To me it is inefficient, spending more time on exchanging a
> miniscule subset of prefixes although there must be some cost of
> introducing filters.

Yes, prefix-lists are handled in mainline quagga as linked lists. This is
highly inefficient.

FWIW, this problem is fixed on the euro_ix_b quagga branch, which
implements prefix-lists as a trie.

Nick
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nick at inex

Jul 25, 2012, 6:49 AM

Post #3 of 3 (238 views)
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Re: Large Prefix-list Performance on Quagga [In reply to]

On 25/07/2012 11:57, Alexis Rosen wrote:
> On Jul 25, 2012, at 4:26 AM, Nick Hilliard wrote:
>> FWIW, this problem is fixed on the euro_ix_b quagga branch, which
>> implements prefix-lists as a trie.
>
> Speaking of which... is there anything like a schedule for merging your branch back into mainline?

it's not ready for merging at the moment, but we are working on making it
ready.

Nick

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