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Date:      Sun, 27 Aug 2000 20:03:55 -0400 (EDT)
From:      Garrett Wollman <wollman@khavrinen.lcs.mit.edu>
To:        Ping Yuan <yuanpinghh@yahoo.com>
Cc:        freebsd-net@FreeBSD.ORG
Subject:   Setting buffer size.
Message-ID:  <200008280003.UAA21054@khavrinen.lcs.mit.edu>
In-Reply-To: <20000827174129.15742.qmail@web1607.mail.yahoo.com>
References:  <20000827174129.15742.qmail@web1607.mail.yahoo.com>

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<<On Sun, 27 Aug 2000 10:41:29 -0700 (PDT), Ping Yuan <yuanpinghh@yahoo.com> said:

> I am now using Freebsd 3.2 as a router. I noticed that
> when the router was busy, more packets would be
> dropped.

This is a fundamental limitation of BSD's network stack and two-level
interrupt scheme.  More memory will not help; when packets are being
dropped, the kernel is already receiving more packets per unit time
than it is capable of forwarding.  See, for exampl, Jeff Mogul's
``Receive Livelock'' paper.

-GAWollman

--
Garrett A. Wollman   | O Siem / We are all family / O Siem / We're all the same
wollman@lcs.mit.edu  | O Siem / The fires of freedom 
Opinions not those of| Dance in the burning flame
MIT, LCS, CRS, or NSA|                     - Susan Aglukark and Chad Irschick


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