From mboxrd@z Thu Jan 1 00:00:00 1970 From: Carsten Wolff Subject: Re: TCP fast retransmit Date: Thu, 15 Dec 2011 08:41:06 +0100 Message-ID: <201112150841.08087.carsten@wolffcarsten.de> References: <2D9E1426-D432-4D08-BF28-FD2615AAEDBA@mpi-bpc.mpg.de> <1323901909.2631.17.camel@edumazet-laptop> Mime-Version: 1.0 Content-Type: Text/Plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Yuchung Cheng , "Esztermann, Ansgar" , "netdev@vger.kernel.org" To: Eric Dumazet Return-path: Received: from h1346787.stratoserver.net ([85.214.49.182]:44873 "EHLO h1346787.stratoserver.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750996Ab1LOHl3 convert rfc822-to-8bit (ORCPT ); Thu, 15 Dec 2011 02:41:29 -0500 In-Reply-To: <1323901909.2631.17.camel@edumazet-laptop> Sender: netdev-owner@vger.kernel.org List-ID: On Wednesday 14 December 2011, Eric Dumazet wrote: > Le mercredi 14 d=C3=A9cembre 2011 =C3=A0 11:00 -0800, Yuchung Cheng a= =C3=A9crit : > > I use tcptrace to check the time sequence and I am puzzled: > > I see a lot of OOO packets too but how can this happen at a sender-= side > > trace? unless the trace is taken close to but not exactly at the se= nder. > > I expect on seeing in-sequence packets but a lots of SACKs plus som= e > > spurious retransmists. >=20 > I understood the trace was a receiver-side one (a linux machine if I = am > not mistaken, while the sender is AIX powered) >=20 > (Looking at timings of ACKS, coming a few us after corresponding data > packet arrival) Oh. Right. This also means, that net.ipv4.tcp_reordering is only availa= ble at=20 the receiver (Linux), which doesn't help, because the reordering robust= ness=20 stuff happens on sender-side. So don't even bother changing that sysctl= =2E Carsten