From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: Socket buffer sizes with autotuning Date: Tue, 22 Apr 2008 20:59:45 -0700 (PDT) Message-ID: <20080422.205945.229828014.davem@davemloft.net> References: <480E8523.4030007@hp.com> <1e41a3230804221917m4af32ed9ice8225c943d3ffa2@mail.gmail.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: rick.jones2@hp.com, netdev@vger.kernel.org To: johnwheffner@gmail.com Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:49413 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1752061AbYDWD7o (ORCPT ); Tue, 22 Apr 2008 23:59:44 -0400 In-Reply-To: <1e41a3230804221917m4af32ed9ice8225c943d3ffa2@mail.gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: From: "John Heffner" Date: Tue, 22 Apr 2008 19:17:39 -0700 > On Tue, Apr 22, 2008 at 5:38 PM, Rick Jones wrote: > > oslowest:~# netstat -an | grep ESTAB > > ... > > tcp 0 2760560 10.208.0.1:40500 10.208.0.45:42049 ESTABLISHED > > ... > > > > Is this expected behaviour? > > What is your interface txqueuelen and mtu? If you have a very large > interface queue, TCP will happily fill it up unless you are using a > delay-based congestion controller. Yes, that's the fundamental problem with loss based congestion control. If there are any queues in the path, TCP will fill them up. Vegas and other similar techniques are able to avoid this, but come with the fundamental flaw that it's easy to get them into situations where they do not respond to increases in pipe space adequately, and thus underperform compared to loss based algorithms.