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.
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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