From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wenji Wu Subject: A Linux TCP SACK Question Date: Thu, 03 Apr 2008 21:54:22 -0700 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7BIT To: netdev@vger.kernel.org Return-path: Received: from mailgw1.fnal.gov ([131.225.111.11]:56832 "EHLO mailgw1.fnal.gov" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751740AbYDDGMH (ORCPT ); Fri, 4 Apr 2008 02:12:07 -0400 Received: from mailav2.fnal.gov (mailav2.fnal.gov [131.225.111.20]) by mailgw1.fnal.gov (iPlanet Messaging Server 5.2 HotFix 2.06 (built Mar 28 2005)) with SMTP id <0JYS00INFAYD6H@mailgw1.fnal.gov> for netdev@vger.kernel.org; Thu, 03 Apr 2008 23:54:23 -0500 (CDT) Received: from mailgw2.fnal.gov ([131.225.111.12]) by mailav2.fnal.gov (SAVSMTP 3.1.7.47) with SMTP id M2008040323542300166 for ; Thu, 03 Apr 2008 23:54:23 -0500 Received: from conversion-daemon.mailgw2.fnal.gov by mailgw2.fnal.gov (iPlanet Messaging Server 5.2 HotFix 2.06 (built Mar 28 2005)) id <0JYS00401AXASX@mailgw2.fnal.gov> (original mail from wenji@fnal.gov) for netdev@vger.kernel.org; Thu, 03 Apr 2008 23:54:23 -0500 (CDT) Received: from fnal.gov (imap2.fnal.gov [131.225.111.7]) by mailgw2.fnal.gov (iPlanet Messaging Server 5.2 HotFix 2.06 (built Mar 28 2005)) with ESMTP id <0JYS0019MAYMIT@mailgw2.fnal.gov> for netdev@vger.kernel.org; Thu, 03 Apr 2008 23:54:22 -0500 (CDT) Content-language: en Content-disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: Hi, Could any body help me out with Linux TCP SACK? Thanks in advance. I run iperf to send traffic from sender to receiver. and add packet reordering in both forward and reverse directions. I found when I turn off the SACK/DSACK option, the throughput is better than with the SACK/DSACK on? How could it happen in this way? did anybody encounter this phenomenon before? thanks, wenji