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Date:      Sun, 18 Jul 1999 00:37:53 +0200
From:      sthaug@nethelp.no
To:        vince@venus.GAIANET.NET
Cc:        tim@storm.digital-rain.com, freebsd-hackers@FreeBSD.ORG
Subject:   Re: poor ethernet performance? 
Message-ID:  <60044.932251073@verdi.nethelp.no>
In-Reply-To: Your message of "Sat, 17 Jul 1999 14:25:41 -0700 (PDT)"
References:  <Pine.BSF.4.05.9907171422550.331-100000@venus.GAIANET.NET>

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> 	It meets the spec when shipped but the bends, curves, temperature
> and other factors do affect the performance.  I guess a good way to test
> the cable is with FreeBSD since it's the only real OS I've seen that can
> do like real world speeds.  The only thing is that has anyone really saw
> 12 Megabytes/sec Full Duplex under FreeBSD?

If you mean mega = 1048576, it's impossible since this is faster than 100
Mbps whichever way you count it.

If you mean mega = 1000000, it depends on which way you're counting. The
"speed of light" for TCP, application to application, on 100 Mbps Ethernet
is 100 * 1460/1538 = 94.93 Mbps. This assumes full duplex.

I've measured 94.87 Mbps myself on full duplex 100BaseTX (back to back
with a crossover cable or through a switch).  This is close enough to
the "speed of light" that I see no point in trying to improve on it...

Steinar Haug, Nethelp consulting, sthaug@nethelp.no


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