Date: Fri, 30 Nov 2001 13:10:13 +0100 From: Bernd Walter <ticso@cicely8.cicely.de> To: Pierre Beyssac <pb@fasterix.freenix.org> Cc: Leo Bicknell <bicknell@ufp.org>, Josh Paetzel <friar_josh@webwarrior.net>, jc@irbs.com, freebsd-hackers@FreeBSD.ORG Subject: Re: FreeBSD performing worse than Linux? Message-ID: <20011130131013.A70828@cicely8.cicely.de> In-Reply-To: <20011130111156.A27621@fasterix.frmug.org> 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> <20011129222809.A67159@ussenterprise.ufp.org> <20011130111156.A27621@fasterix.frmug.org>
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On Fri, Nov 30, 2001 at 11:11:56AM +0100, Pierre Beyssac wrote: > On Thu, Nov 29, 2001 at 10:28:09PM -0500, Leo Bicknell wrote: > > 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. > > It's where I don't quite agree: for a bulk transfer, there is no > RTT to account for, you only need to take into account the one-way > delay, TCP does the rest for you assuming the window is large enough. Asume you have 10ms one way delay and an RTT of 20ms. Lets asume your windowsize fits exactly the one way delay. You start sending data until the send window is exhaustet. You have been seending 10ms from the begining and at that time the first packet of you stream reaches the receiver. Now you have to stop sending data for 10ms because you have to wait for the first acknowledge to arive to free some space of the window - if the receiver delays ack you have to wait longer. You can easily see that you need to take RTT + delayed-ack-time into acount. -- B.Walter COSMO-Project http://www.cosmo-project.de ticso@cicely.de Usergroup info@cosmo-project.de To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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