From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 3 Sep 2001 13:59:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 3 Sep 2001 13:59:22 -0400 Received: from [195.89.159.99] ([195.89.159.99]:57844 "EHLO kushida.degree2.com") by vger.kernel.org with ESMTP id ; Mon, 3 Sep 2001 13:59:07 -0400 Date: Mon, 3 Sep 2001 18:57:00 +0100 From: Jamie Lokier To: kuznet@ms2.inr.ac.ru Cc: davem@redhat.com, ak@muc.de, linux-kernel@vger.kernel.org Subject: Re: Excessive TCP retransmits over lossless, high latency link Message-ID: <20010903185700.A12529@thefinal.cern.ch> In-Reply-To: <20010901210212.A3361@thefinal.cern.ch> <200109031714.VAA24484@ms2.inr.ac.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <200109031714.VAA24484@ms2.inr.ac.ru>; from kuznet@ms2.inr.ac.ru on Mon, Sep 03, 2001 at 09:14:47PM +0400 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org kuznet@ms2.inr.ac.ru wrote: > > Yes, definitely. Btw, I saw a ping round trip time of 162s just now. > > I do not understand, do you share this link with someone or > ping over tcp connection? I was doing ping with the TCP connection going. When there is no TCP connection, ping time is 1-1.5 seconds. > > I saw very few retransmits in a single message download. SACK appears > > occasionally. I don't really understand the local reaction to SACK, or > > why a SACK option appears in one ACK sent locally and not the following > > ACK, even though the SACK mentions data that does not arrive between the > > two locally sent ACKs. > > But I do not see _any_ sacks in your tcpdumps. Sorry, you are right. I did see an sack, but not in this trace. > > The throughput difference was obvious: POP3 negotiation + 30k message + > > headers took: > > > > 5 min 31 sec downloading unknown OS -> Linux 2.4.7 > > 2 min 15 sec downloading Linux 2.4.2 -> Linux 2.4.7 > > It is dominated by rtt, one rtt per segment. It is very strange > that cwnd does not want to open. Maybe, it is worth to tcpdump at proxy. Do you mean that you want to see the Linux -> Linux connection, with tcpdumps at both ends? -- Jamie