From mboxrd@z Thu Jan 1 00:00:00 1970 From: "David S. Miller" Subject: Re: tune back idle cwnd closing? Date: Wed, 26 Apr 2006 14:45:40 -0700 (PDT) Message-ID: <20060426.144540.39973302.davem@davemloft.net> References: <44493980.1040708@oracle.com> <444E31D9.1010705@psc.edu> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: zach.brown@oracle.com, netdev@vger.kernel.org Return-path: Received: from dsl027-180-168.sfo1.dsl.speakeasy.net ([216.27.180.168]:11995 "EHLO sunset.davemloft.net") by vger.kernel.org with ESMTP id S932245AbWDZVpo (ORCPT ); Wed, 26 Apr 2006 17:45:44 -0400 To: jheffner@psc.edu In-Reply-To: <444E31D9.1010705@psc.edu> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org From: John Heffner Date: Tue, 25 Apr 2006 10:27:37 -0400 > Yours is the first complaint of this kind I recall seeing, but I've > expected for a while someone would have this type of problem. RFC2861 > seems conceptually nice at first, but there are a few things about it > that bother me. One thing in particular is that a naturally bursty > application (like yours) will actually perform better by padding its > connection with junk data whenever it doesn't have real data to send. > Or equivalently, it's punished for not sending data when it doesn't need > to. I also think it may not do much good when there are connections > with significantly different RTTs. > > Given that RFC2681 is Experimental (and I'm not aware of any current > efforts in the IETF to push it to the standard track), IHMO it would not > be inappropriate to make this behavior controlled via sysctl. I have to respectfully disagree. This is the price you pay when the network's congestion is being measured by probing, information becomes stale over time if you don't send any probes. And this change of congestion state is real and happens frequently for most end to end users. When you're bursty application is not sending, other flows can take up the pipe space you are not using, and you must reprobe to figure that out.