From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Heffner Subject: Re: [PATCH] make _minimum_ TCP retransmission timeout configurable Date: Wed, 29 Aug 2007 19:44:23 -0400 Message-ID: <46D604D7.6090200@psc.edu> References: <46D5F32F.2070502@hp.com> <20070829.153503.18295527.davem@davemloft.net> <46D5FBF3.5050700@hp.com> <20070829.161528.38309258.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: rick.jones2@hp.com, ian.mcdonald@jandi.co.nz, netdev@vger.kernel.org, ilpo.jarvinen@helsinki.fi To: David Miller Return-path: Received: from mailer1.psc.edu ([128.182.58.100]:53495 "EHLO mailer1.psc.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750802AbXH2Xom (ORCPT ); Wed, 29 Aug 2007 19:44:42 -0400 In-Reply-To: <20070829.161528.38309258.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org David Miller wrote: > From: Rick Jones > Date: Wed, 29 Aug 2007 16:06:27 -0700 > >> I belive the biggest component comes from link-layer retransmissions. >> There can also be some short outtages thanks to signal blocking, >> tunnels, people with big hats and whatnot that the link-layer >> retransmissions are trying to address. The three seconds seems to be a >> value that gives the certainty that 99 times out of 10 the segment was >> indeed lost. >> >> The trace I've been sent shows clean RTTs ranging from ~200 milliseconds >> to ~7000 milliseconds. > > Thanks for the info. > > It's pretty easy to generate examples where we might have some sockets > talking over interfaces on such a network and others which are not. > Therefore, if we do this, a per-route metric is probably the best bet. This is exactly what I was thinking. It might even help discourage users from playing with this setting who should not. ;) -John