Date: Thu, 29 Nov 2001 22:28:09 -0500 From: Leo Bicknell <bicknell@ufp.org> To: Pierre Beyssac <pb@fasterix.freenix.org> Cc: Josh Paetzel <friar_josh@webwarrior.net>, jc@irbs.com, freebsd-hackers@FreeBSD.ORG Subject: Re: FreeBSD performing worse than Linux? Message-ID: <20011129222809.A67159@ussenterprise.ufp.org> In-Reply-To: <20011130032345.A23415@fasterix.frmug.org>; from pb@fasterix.freenix.org on Fri, Nov 30, 2001 at 03:23:45AM %2B0100 References: <20011128153817.T61580@monorchid.lemis.com> <15364.38174.938500.946169@caddis.yogotech.com> <20011129004234.A16101@exuma.irbs.com> <20011130010354.A21307@fasterix.frmug.org> <20011129184414.F522@twincat.vladsempire.net> <20011130022547.A21889@fasterix.frmug.org> <20011129204225.A63957@ussenterprise.ufp.org> <20011130032345.A23415@fasterix.frmug.org>
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On Fri, Nov 30, 2001 at 03:23:45AM +0100, Pierre Beyssac wrote:
> I can't reproduce this result, 16K fills a T1 for 11 ms, which is
> 22000 km (at 2/3 of light speed), enough to get halfway round the
> earth...
Your math is a little funny.
4000 km New York to LA
c = 300,000 km/sec
Speed of light in fiber, approximately .66 c, or 198,000 km/sec.
Approximate sum of buffering + serialization delay in the network,
is a 15% penalty, or 168,300 kph. total speed.
4000 km one way == 8000 km two way, 8000 / 168300 = 47ms in my book,
theoretial optimum.
With an RTT of 47ms, you can move 16k per RTT, or or about 340k/sec.
* If you find a cross country RTT of 47 ms I'll personally send you
$20. around 60-65 is normal for "good circuits", and 70-90 is
not wholely unusual.
* The 340k/sec assumes perfect network conditions, that is no dropped
or delayed packets.
Please search the archives. There are reams of information about
this.
--
Leo Bicknell - bicknell@ufp.org - CCIE 3440
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