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Date:      Sun, 29 Feb 2004 00:13:21 -0600 (CST)
From:      Mike Silbersack <silby@silby.com>
To:        Don Bowman <don@sandvine.com>
Cc:        freebsd-hackers@freebsd.org
Subject:   RE: em0, polling performance, P4 2.8ghz FSB 800mhz
Message-ID:  <20040229001251.Q11460@odysseus.silby.com>
In-Reply-To: <FE045D4D9F7AED4CBFF1B3B813C85337045D8307@mail.sandvine.com>
References:  <FE045D4D9F7AED4CBFF1B3B813C85337045D8307@mail.sandvine.com>

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On Sat, 28 Feb 2004, Don Bowman wrote:

> You could use ipfw to limit the damage of a syn flood, e.g.
> a keep-state rule with a limit of ~2-5 per source IP, lower the
> timeouts, increase the hash buckets in ipfw, etc. This would
> use a mask on src-ip of all bits.
> something like:
> allow tcp from any to any setup limit src-addr 2
>
> this would only allow 2 concurrent TCP sessions per unique
> source address. Depends on the syn flood you are expecting
> to experience. You could also use dummynet to shape syn
> traffic to a fixed level i suppose.

Does that really help?  If so, we need to optimize the syncache. :(

Mike "Silby" Silbersack



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