Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965376AbWHOQFl (ORCPT ); Tue, 15 Aug 2006 12:05:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965380AbWHOQFk (ORCPT ); Tue, 15 Aug 2006 12:05:40 -0400 Received: from mail.everytruckjob.com ([198.87.235.158]:57269 "EHLO mail.everytruckjob.com") by vger.kernel.org with ESMTP id S965376AbWHOQFk (ORCPT ); Tue, 15 Aug 2006 12:05:40 -0400 Message-ID: <44E1F0CD.7000003@everytruckjob.com> Date: Tue, 15 Aug 2006 11:05:33 -0500 From: Mark Reidenbach User-Agent: Thunderbird 1.5.0.5 (Windows/20060719) MIME-Version: 1.0 To: linux-kernel@vger.kernel.org Subject: How to find a sick router with 2.6.17+ and tcp_window_scaling enabled Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7346 Lines: 151 I had made an earlier post concerning very poor network performance after upgrading to 2.6.17 and later kernels. The solution provided by the e1000 developers was that it was in fact a change to the default tcp window scaling settings and that there was a router somewhere between my computer and its destination. After scouring the net for many days trying to find an answer as to how to find the broken router, I've come up empty and there are many references as to why you don't want to disable window scaling completely which so far has been my only working solution. Can anyone give instructions or references as to what the requirements are for a router to work (specifically Cisco routers)? Is there a minimum required IOS or certain commands that must be enabled such as any of the following? ip tcp window-size 8388480 ip tcp selective-ack ip tcp timestamp Does anyone have a way to find the broken router if you are not running the networks involved? I'm almost positive it's our T1 provider, but after being on the phone with them for a couple hours they insist it's not their problem and that their routers are configured properly (what else would you expect them to say after all). There are only 5 hops in the traceroute between us and a test file they have set. Below is the traceroute info: 1 192.168.13.1 (192.168.13.1) 0.319 ms 0.332 ms 0.245 ms 2 nsc69.38.0-110.newsouth.net (69.38.0.110) 2.484 ms 2.107 ms 1.985 ms 3 nsc69.38.3-17.newsouth.net (69.38.3.17) 6.612 ms 6.403 ms 5.986 ms 4 66.64.228.106.nw.nuvox.net (66.64.228.106) 15.357 ms 14.885 ms 15.353 ms 5 virt4.rhetoric.nuvox.net (66.83.21.33) 14.982 ms 14.880 ms 15.102 ms The only information I have on the routers is: 192.168.13.1: This is our office router and is a Cisco 1811 running 12.3(8)YI1. 69.38.0.110: T1 provider's router installed at our office. This is a Cisco 2600 series that I was told was running 12.2(10)R even though I can't find a 10R release on Cisco's website. My computer has 2GB of ram if that helps since it seems the new defaults are based on system ram. Below is the start of a tcpdump when trying to retrieve the test file from my T1 provider's server with tcp_window_scaling = 1. I'm somewhat confused why performance drops from more than 225kB/s with window scaling disabled to less than 50kB/s with it enabled since it looks like the test server acks with a wscale of 0 and I thought that would have the same behavior as setting tcp_window_scaling to 0. tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes 10:49:01.890275 IP backup.truckersexit.com.55805 > virt4.rhetoric.nuvox.net.http: S 906926812:906926812(0) win 5840 10:49:01.905118 IP virt4.rhetoric.nuvox.net.http > backup.truckersexit.com.55805: S 4149240349:4149240349(0) ack 906926813 win 5792 10:49:01.905128 IP backup.truckersexit.com.55805 > virt4.rhetoric.nuvox.net.http: . ack 1 win 46 10:49:01.905229 IP backup.truckersexit.com.55805 > virt4.rhetoric.nuvox.net.http: P 1:115(114) ack 1 win 46 10:49:01.920359 IP virt4.rhetoric.nuvox.net.http > backup.truckersexit.com.55805: . ack 115 win 5792 10:49:01.932477 IP virt4.rhetoric.nuvox.net.http > backup.truckersexit.com.55805: . 1:1449(1448) ack 115 win 5792 10:49:01.932484 IP backup.truckersexit.com.55805 > virt4.rhetoric.nuvox.net.http: . ack 1449 win 69 10:49:01.938473 IP virt4.rhetoric.nuvox.net.http > backup.truckersexit.com.55805: . 1449:2897(1448) ack 115 win 5792 10:49:01.938481 IP backup.truckersexit.com.55805 > virt4.rhetoric.nuvox.net.http: . ack 2897 win 91 10:49:01.956837 IP virt4.rhetoric.nuvox.net.http > backup.truckersexit.com.55805: P 2897:4345(1448) ack 115 win 5792 10:49:01.956843 IP backup.truckersexit.com.55805 > virt4.rhetoric.nuvox.net.http: . ack 4345 win 114 10:49:01.962834 IP virt4.rhetoric.nuvox.net.http > backup.truckersexit.com.55805: . 4345:5793(1448) ack 115 win 5792 10:49:01.962839 IP backup.truckersexit.com.55805 > virt4.rhetoric.nuvox.net.http: . ack 5793 win 137 10:49:01.968830 IP virt4.rhetoric.nuvox.net.http > backup.truckersexit.com.55805: . 5793:7241(1448) ack 115 win 5792 10:49:01.968835 IP backup.truckersexit.com.55805 > virt4.rhetoric.nuvox.net.http: . ack 7241 win 159 10:49:01.974952 IP virt4.rhetoric.nuvox.net.http > backup.truckersexit.com.55805: . 7241:8689(1448) ack 115 win 5792 10:49:01.974956 IP backup.truckersexit.com.55805 > virt4.rhetoric.nuvox.net.http: . ack 8689 win 182 10:49:01.981323 IP virt4.rhetoric.nuvox.net.http > backup.truckersexit.com.55805: . 8689:10137(1448) ack 115 win 5792 10:49:01.981327 IP backup.truckersexit.com.55805 > virt4.rhetoric.nuvox.net.http: . ack 10137 win 204 10:49:01.987319 IP virt4.rhetoric.nuvox.net.http > backup.truckersexit.com.55805: P 10137:11585(1448) ack 115 win 5792 10:49:01.987323 IP backup.truckersexit.com.55805 > virt4.rhetoric.nuvox.net.http: . ack 11585 win 227 10:49:01.993316 IP virt4.rhetoric.nuvox.net.http > backup.truckersexit.com.55805: . 11585:13033(1448) ack 115 win 5792 10:49:01.993320 IP backup.truckersexit.com.55805 > virt4.rhetoric.nuvox.net.http: . ack 13033 win 250 10:49:01.999437 IP virt4.rhetoric.nuvox.net.http > backup.truckersexit.com.55805: P 13033:14481(1448) ack 115 win 5792 10:49:01.999441 IP backup.truckersexit.com.55805 > virt4.rhetoric.nuvox.net.http: . ack 14481 win 272 10:49:02.005434 IP virt4.rhetoric.nuvox.net.http > backup.truckersexit.com.55805: . 14481:15929(1448) ack 115 win 5792 10:49:02.005438 IP backup.truckersexit.com.55805 > virt4.rhetoric.nuvox.net.http: . ack 15929 win 295 10:49:02.011306 IP virt4.rhetoric.nuvox.net.http > backup.truckersexit.com.55805: . 15929:17377(1448) ack 115 win 5792 Please CC me on any replies as I'm not subscribed to the list. -- Mark Reidenbach EveryTruckJob.com M.Reidenbach@EveryTruckJob.com Phone: (205)722-9112 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/