Date: Wed, 24 Jan 2001 21:52:51 -0600 (CST) From: Jonathan Lemon <jlemon@flugsvamp.com> To: genuine@ma4.justnet.ne.jp, net@freebsd.org Subject: Re: estimation of RTT,RTO from tcpcb parameter Message-ID: <200101250352.f0P3qpV49010@prism.flugsvamp.com> In-Reply-To: <local.mail.freebsd-net/3A6F913A320.7B49GENUINE@ma4.justnet.ne.jp> References: <local.mail.freebsd-net/3A6F72E71D6.7B48GENUINE@ma4.justnet.ne.jp> <local.mail.freebsd-net/200101250133.UAA73836@khavrinen.lcs.mit.edu>
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In article <local.mail.freebsd-net/3A6F913A320.7B49GENUINE@ma4.justnet.ne.jp> you write: >Thank you very much for your kindly advise. > >>The system timer ticks at a rate of 100 Hz on all IA32 processors. (I >>believe on Alphas it ticks at 1024 Hz but I may be imagining it.) >>Thus, the period is either 10 ms or 0.98 ms. >> >>In historic versions of FreeBSD, most TCP timers ticked at 2 Hz while >>the others ticked at 5 Hz. This was changed in advance of FreeBSD >>4.0. > >I see. >Anyway, it seems to be difficult that estimating RTT, RTO within a LAN >envirounment (such as Gigabit connection). >Of course, this time scale may be valid for general internet envirounment. >I'll study more. The math for RTT calculations is explained somewhere in Van Jacobsen's congestion avoidance & control paper, I believe. The equations have since been modified slightly since then, but give the basic idea. -- Jonathan To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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