From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752748Ab1LQXSM (ORCPT ); Sat, 17 Dec 2011 18:18:12 -0500 Received: from mail-iy0-f174.google.com ([209.85.210.174]:33623 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752007Ab1LQXSK (ORCPT ); Sat, 17 Dec 2011 18:18:10 -0500 Message-ID: <4EED232D.3010208@lwfinger.net> Date: Sat, 17 Dec 2011 17:18:05 -0600 From: Larry Finger User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:8.0) Gecko/20111105 Thunderbird/8.0 MIME-Version: 1.0 To: wireless , LKML Subject: Question about TCP Checksum errors Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In https://bugzilla.novell.com/show_bug.cgi?id=718736, a user reports that his network using an RTL8188CE becomes very slow under "heavy" load. This condition started when he updated from openSUSE 11.4 to 12.1. The kernels involved are 2.6.37 and 3.1. I am unable to duplicate the problem. Packet capture with Wireshark shows that the slow down is due to retransmissions due to TCP checksum errors. I found nothing to explain the situation with a Google search, thus I am asking here. I put heavy in quotes because the traffic is from a web browser to yahoo.com, thus the potential throughput is not very high. As far as I know, this checksum is generated in a higher layer of the network stack, and that data is just passed through the 802.11 layer, and the wireless driver. Is this correct? Anyone have any ideas on where to look for the problem? Thanks, Larry