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 From:  "Chad R. Larson" <clarson at eldocomp dot com>
 To:  Manuel Kasper <mk at neon1 dot net>, Justin Albstmeijer <justin at VLAMea dot nl>
 Cc:  "m0n0wall at lists dot m0n0 dot ch" <m0n0wall at lists dot m0n0 dot ch>
 Subject:  Re: [m0n0wall] m0n0wall + net4501 keeps rebooting
 Date:  Tue, 30 Dec 2003 13:31:47 -0700
At 12:47 PM 12/29/2003, Manuel Kasper wrote:
>OK, you got me worried - I did some testing with a net4511, and sure 
>enough, I was able to kill it with a single TCP connection at maximum 
>speed (which turned out to be about 16 Mbps) after only 25 seconds. It 
>just reset, no kernel panic, no messages, no nothing. Scary! I tried with 
>BIOS versions 1.15a and 1.22 - no difference (as expected).

Sounds like an overrun to me.  That would explain why a net4801 wouldn't 
crash--it's a lot faster.  Is it possible to do a netstat about 10 seconds 
in and see how deep the send queue is?  Also, it would be interesting what 
effect traffic shaping would have.  I suspect limiting the input side to 
something like 12Mbps would fix it.  Does specifying a larger than default 
value for NMBCLUSTERS and NMBUFS change the behavior?  If all this is true, 
it would mean that FreeBSD is not dealing well with a too deep send 
queue.  That would be worth a bug report.  It should at least punt out a 
message before barfing; dropping packets and not crashing would be even better.

I would point out, however, that the lowly 486 in the net4501 still runs 
something like ten times as fast as a T1.  Another sign that the FreeBSD 
network stack rocks.


         -crl
--
Chad R. Larson (CRL22)    chad at eldocomp dot com
   Eldorado Computing, Inc.   602-604-3100
      5353 North 16th Street, Suite 400
        Phoenix, Arizona   85016-3228

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