Date: Sat, 29 Jun 2002 12:22:32 -0700 (PDT) From: John Polstra <jdp@polstra.com> To: hardware@freebsd.org Cc: jack_zhangcl@hotmail.com Subject: Re: wscale issue on netperf testing Message-ID: <200206291922.g5TJMW1h007693@vashon.polstra.com> In-Reply-To: <F94OxbCJnEMzAUor03u00000304@hotmail.com> References: <F94OxbCJnEMzAUor03u00000304@hotmail.com>
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In article <F94OxbCJnEMzAUor03u00000304@hotmail.com>, zhang jack <jack_zhangcl@hotmail.com> wrote: > Hi, > > I am testing giga bits NICs with netperf,two machine have the same install, > but when I start netperf,using tcpdump to listen,the wscale is different. > > giga# tcpdump -vv -n -i em0 -c 100 > tcpdump: listening on em0 > 19:28:35.946808 10.0.0.1.49187 > 10.0.0.2.12865: S [tcp sum ok] > 3414289560:3414289560(0) win 65535 <mss 15960,nop,wscale > 4,nop,nop,timestamp 336910 0> (ttl 64, id 12226, len 60) > 19:28:35.946877 10.0.0.2.12865 > 10.0.0.1.49187: S [bad tcp cksum 751c!] > 2862099494:2862099494(0) ack 3414289561 win 57344 <mss 15960,nop,wscale > 0,nop,nop,timestamp 346195 336910> (ttl 64, id 27150, len 60) Check again, and I think you will discover that the two machines do not have the same install. In FreeBSD 4-stable the default receive window was reduced from 64k to 57k on 7 June 2002. One of your machines has that change, and the other one does not have it. Here is the explanation of the change from the commit log message: revision 1.51.2.13 date: 2002/06/07 20:23:44; author: obrien; state: Exp; lines: +1 -1 IPfiler has problems with its keep state when the windows size is 64k. So reduce it to 57k for now. It should remain 64k in -CURRENT so we can force a fix in broken software. There is nice explanation in the PR about the environment in which the bug happens. Approved by: murray PR: 34801 Submitted by: AMAKAWA Shuhei <sa264@cam.ac.uk> You can easily change the receive window with the sysctl variable "net.inet.tcp.recvspace". John -- John Polstra John D. Polstra & Co., Inc. Seattle, Washington USA "Disappointment is a good sign of basic intelligence." -- Chögyam Trungpa To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hardware" in the body of the message
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