From owner-cvs-all Wed Jul 17 21:17: 3 2002 Delivered-To: cvs-all@freebsd.org Received: from mx1.FreeBSD.org (mx1.FreeBSD.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 7563F37B405; Wed, 17 Jul 2002 21:16:54 -0700 (PDT) Received: from apollo.backplane.com (apollo.backplane.com [216.240.41.2]) by mx1.FreeBSD.org (Postfix) with ESMTP id 2D06A43E31; Wed, 17 Jul 2002 21:16:54 -0700 (PDT) (envelope-from dillon@apollo.backplane.com) Received: from apollo.backplane.com (localhost [127.0.0.1]) by apollo.backplane.com (8.12.5/8.12.4) with ESMTP id g6I4GrCV005312; Wed, 17 Jul 2002 21:16:53 -0700 (PDT) (envelope-from dillon@apollo.backplane.com) Received: (from dillon@localhost) by apollo.backplane.com (8.12.5/8.12.4/Submit) id g6I4GrLM005311; Wed, 17 Jul 2002 21:16:53 -0700 (PDT) (envelope-from dillon) Date: Wed, 17 Jul 2002 21:16:53 -0700 (PDT) From: Matthew Dillon Message-Id: <200207180416.g6I4GrLM005311@apollo.backplane.com> To: Mike Silbersack Cc: cvs-committers@FreeBSD.ORG, Subject: Re: cvs commit: src/sys/netinet tcp_timer.h References: <20020717220320.F83856-100000@patrocles.silby.com> Sender: owner-cvs-all@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG :The RTO is not what is _causing_ problems: the packet loss which requires :the use of a RTO is what causes the problem. You're not going to solve :such packet loss by blasting out retransmissions ASAP, and such a drastic :change will affect other situations (such as a short cable/hub/router :outage) in profound ways. I'm not sure what your point is here. Retransmit timeouts are only an issue when packet loss is present. We can't just declare packet loss to be bad and ignore it, after all. And I have to disagree with your characterization of the retransmit as 'blasting it out ASAP'. That is not what occurs. The RTO mechanism is fairly conservative. :Tweaking the 1 second timeout down to 200ms is relatively simple. :Allowing the RTO to go all the way down to 3*rtt is much more drastic, and :could have many unexpected sideeffects that will be hard to track down. : :Mike "Silby" Silbersack The whole point of the RTO calculation is to avoid the side effects. If the side effects go beyond triviality then our RTO calculation is not being done properly. It's that simple. Either our RTO calculation is right or it is wrong. -Matt Matthew Dillon To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message