Date: Sat, 29 Nov 2008 12:39:49 -0800 (PST) From: Venkat Venkatsubra <venkatvenkatsubra@yahoo.com> To: David Malone <dwmalone@maths.tcd.ie> Cc: Rui Paulo <rpaulo@fnop.net>, freebsd-net@freebsd.org, Kevin Oberman <oberman@es.net> Subject: Re: FreeBSD Window updates Message-ID: <10716.94191.qm@web58304.mail.re3.yahoo.com> References: <200811291746.aa88825@walton.maths.tcd.ie>
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Hi David,=0A=0AAssuming each of these 5 window updates are sent after the a= pps=0Acompleted the=A0read that it issued, what's the buffer size the apps = is passing=0Ato the read ? If it is small, could that be increased ?=0A=0AB= ut I agree with you that there is room for optimizing sending of these wind= ow updates.=0A=0A(Since I don't know the window scale factor for the connec= tion, I couldn't figure out=0Ahow much each of the window updates was openi= ng up the window.)=0A=0AVenkat=0A=0A=0A________________________________=0AF= rom: David Malone <dwmalone@maths.tcd.ie>=0ATo: Venkat Venkatsubra <venkatv= enkatsubra@yahoo.com>=0ACc: Rui Paulo <rpaulo@fnop.net>; freebsd-net@freebs= d.org; Kevin Oberman <oberman@es.net>=0ASent: Saturday, November 29, 2008 1= 1:46:30 AM=0ASubject: Re: FreeBSD Window updates=0A=0AI've got an example e= xtract tcpdump of this at the end of the mail=0A- here 6 ACKs are sent, 5 o= f which are pure window updates and=0Aseveral are 2us apart!=0A=0AI think t= he easy option is to delete the code that generates explicit=0Awindow updat= es if the window moves by 2*MSS. We then should be doing=0Asomething simila= r to Linux. The other easy alternative would be to=0Aadd a sysclt that lets= us generate an window update every N*MSS and=0Aby default set it to someth= ing big, like 10 or 100. That should=0Aeffectively eliminate the updates du= ring bulk data transfer, but=0Amay still generate some window updates after= a loss.=0A=0ANormal ACKing for driving congestion control shouldn't be imp= acted=0Aby either of these suggested changes.=0A=0A=A0=A0=A0 David.=0A=0A12= 27622713.276609 172.16.2.2.5002 > 172.16.1.51.39077: . ack 144097745 win 40= 798 <nop,nop,timestamp 5365425 5103763> (DF)=0A1227622713.276611 172.16.2.2= .5002 > 172.16.1.51.39077: . ack 144097745 win 40830 <nop,nop,timestamp 536= 5425 5103763> (DF)=0A1227622713.276613 172.16.2.2.5002 > 172.16.1.51.39077:= . ack 144097745 win 40862 <nop,nop,timestamp 5365425 5103763> (DF)=0A12276= 22713.276615 172.16.2.2.5002 > 172.16.1.51.39077: . ack 144097745 win 40894= <nop,nop,timestamp 5365425 5103763> (DF)=0A1227622713.276852 172.16.2.2.50= 02 > 172.16.1.51.39077: . ack 144097745 win 40926 <nop,nop,timestamp 536542= 5 5103763> (DF)=0A1227622713.276855 172.16.2.2.5002 > 172.16.1.51.39077: . = ack 144097745 win 40958 <nop,nop,timestamp 5365425 5103763> (DF)=0A12276227= 13.296585 172.16.2.2.5002 > 172.16.1.51.39077: . ack 144100641 win 40956 <n= op,nop,timestamp 5365445 5103766> (DF)=0A__________________________________= _____________=0Afreebsd-net@freebsd.org mailing list=0Ahttp://lists.freebsd= .org/mailman/listinfo/freebsd-net=0ATo unsubscribe, send any mail to "freeb= sd-net-unsubscribe@freebsd.org"=0A=0A=0A=0A
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