Date: Wed, 9 Jul 2003 10:56:33 -0700 (PDT) From: Kevin Stevens <Kevin_Stevens@pursued-with.net> To: Max Clark <max.clark@media.net> Cc: freebsd-questions@freebsd.org Subject: Re: How do I max a 6Mbps link Message-ID: <20030709104404.P8402@babelfish.pursued-with.net> In-Reply-To: <ILENIMHFIPIBHJLCDEHKCEEBCJAA.max.clark@media.net> References: <ILENIMHFIPIBHJLCDEHKCEEBCJAA.max.clark@media.net>
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On Wed, 9 Jul 2003, Max Clark wrote: > Hi all, > > What configuration changes do I need to make to two freebsd-stable boxes to > fully max out a 6Mbps/220ms network link? This is for bulk 500+MB file > transfers. You need to increase the maximum TCP window size setting (not sure what sysctl it is) to around 256KB to accommodate the bandwidth/latency product. In brief, 6Mb/1500B frames = 500 frames/sec. Using 250ms for simplicity, you need a large enough TCP window to handle 1/4 of that (125 frames x 1500 bytes/frame = 183KB, round up to 256KB) to permit continuous streaming. Note that TCP windows actually only go to 64KB, you need to use TCP window scaling as a multiplier to go beyond that. Both stations must support it. You can find more info on this on the web, look for high-latency/high-bandwidth. KeS
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