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, 14 May 2001 12:19:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 14 May 2001 12:19:39 -0400 Received: from sunmail.canal-plus.fr ([194.2.208.66]:54673 "EHLO sunmail.canal-plus.fr") by vger.kernel.org with ESMTP id ; Mon, 14 May 2001 12:19:34 -0400 Date: Mon, 14 May 2001 18:19:26 +0200 From: tdanis@canal-plus.fr To: linux-kernel@vger.kernel.org Subject: Re: Linux TCP impotency Message-ID: <20010514181926.A31101@canal-plus.fr> In-Reply-To: <20010513213853.A5700@ghost.btnet.cz> <20010513225415.A4950@home.ds9a.nl> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 1.0.1i In-Reply-To: <20010513225415.A4950@home.ds9a.nl>; from ahu@ds9a.nl on Sun, May 13, 2001 at 10:54:15PM +0200 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, May 13, 2001 at 10:54:15PM +0200, ahu@ds9a.nl wrote: > On Sun, May 13, 2001 at 09:38:53PM +0200, clock@ghost.btnet.cz wrote: > > Using 2.2.19 I discovered that running two simultaneous scp's (uses up whole > > capacity in TCP traffic) on a 115200bps full duplex serial port nullmodem cable > > causes the earlier started one to survive and the later to starve. Running bcp > > instead of the second (which uses UDP) at 11000 bytes per second caused the > > utilization in both directions to go up nearly to 100%. > > > > Is this a normal TCP stack behaviour? > > Might very well be. Read about different forms of (class based) queuing > which try (and succeed) to improve IP in this respect. TCP is not fair and > IP has no intrinsic features to help you. http://ds9a.nl/2.4Routing contains > some explanations and links. > > SFQ sounds like it might fit your bill. > > Regards, > > bert > > -- > http://www.PowerDNS.com Versatile DNS Services > Trilab The Technology People > 'SYN! .. SYN|ACK! .. ACK!' - the mating call of the internet > - I was about to report the same 'od' behaviour : I have 3 machines, connected via a HUB at 100 Mb/s half duplex. From machine A : rsh B dd if=/dev/zero bs=8192 | dd of=/dev/null => transfert around 10/11 MB/s (B => A) Now, I start a second transfert from machine C : rsh B dd if=/dev/zero bs=8192 | dd of=/dev/null => transfert around 10/11 MB/s between B and C, almost nothing between A and B (ie, the connexion is stalled between A and B). If I stop the second transfert, I takes many seconds for the transfert to restart between A and B. On a highly saturated network, I have already seen such a behavior. Is that related to the IP adresses, the lowest being served first ? A+, -- Thierry Danis