From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lists.gentoo.org (pigeon.gentoo.org [208.92.234.80]) by finch.gentoo.org (Postfix) with ESMTP id 92AA9198005 for ; Fri, 22 Feb 2013 14:36:32 +0000 (UTC) Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id 44B7B21C03A; Fri, 22 Feb 2013 14:36:23 +0000 (UTC) Received: from mta-2.ms.rz.rwth-aachen.de (mta-2.ms.rz.rwth-aachen.de [134.130.7.73]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by pigeon.gentoo.org (Postfix) with ESMTPS id 8AC6321C003 for ; Fri, 22 Feb 2013 14:36:21 +0000 (UTC) Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-user@lists.gentoo.org Reply-to: gentoo-user@lists.gentoo.org MIME-version: 1.0 Content-transfer-encoding: 7BIT Content-disposition: inline Content-type: text/plain; charset=us-ascii; DelSp=Yes; Format=Flowed Received: from mx-out-1.rwth-aachen.de ([134.130.5.186]) by mta-2.ms.rz.RWTH-Aachen.de (Sun Java(tm) System Messaging Server 6.3-7.04 (built Sep 26 2008)) with ESMTP id <0MIM00HR0LWK2AE0@mta-2.ms.rz.RWTH-Aachen.de> for gentoo-user@lists.gentoo.org; Fri, 22 Feb 2013 15:36:20 +0100 (CET) X-IronPort-AV: E=Sophos;i="4.84,715,1355094000"; d="scan'208";a="211671465" Received: from relay-2.ms.rz.rwth-aachen.de (HELO relay.rwth-aachen.de) ([134.130.7.75]) by mx-1.rz.rwth-aachen.de with ESMTP; Fri, 22 Feb 2013 15:36:20 +0100 Received: from numa-i.igpm.rwth-aachen.de (numa-i.igpm.rwth-aachen.de [134.130.161.252]) by relay.rwth-aachen.de (8.14.4+Sun/8.13.8/1) with ESMTP id r1MEaKAk007064 for ; Fri, 22 Feb 2013 15:36:20 +0100 (CET) Received: from numa-i (localhost [127.0.0.1]) by numa-i.igpm.rwth-aachen.de (Postfix) with ESMTP id EB424BC5 for ; Fri, 22 Feb 2013 15:36:22 +0100 (CET) Date: Fri, 22 Feb 2013 15:36:22 +0100 From: Helmut Jarausch Subject: Re: [gentoo-user] Slow local network - how to debug? To: gentoo-user@lists.gentoo.org In-reply-to: <201302221355.22320.michaelkintzios@gmail.com> X-Mailer: Balsa 2.4.91-7-g3440dfb Message-id: <1361543782.23748.1@numa-i> X-Archives-Salt: 244c050e-6e23-48a8-8294-ac3ac4b25adc X-Archives-Hash: 56d827174d5cb13d3c3fd8a7b2c79951 On 02/22/2013 02:55:07 PM, Mick wrote: > On Friday 22 Feb 2013 08:04:38 Helmut Jarausch wrote: > > Hi, > > > > I have no experiences in debugging a slow network. > > > > At home, I have a router which is connected to my telephone line via > > VDSL2. > > I have 2 PCs one of which is connected by an ethernet cable (i.e. > > wired) while the other > > one uses a wireless connection which is specified as 56 Mbit/s. > > > > When copying data from one machine to the other one I see varying > > speeds from only 0.5 Mbits/s up to > > more than 20 Mbits/s. I have no idea why it is so slow some times. > > There are no other wireless devices nearby. > > Where do you see these transfer speeds? On the wired machine, or on > the > wireless machine? > > What do you use to check the transfer speed? One tool is ttcp which is very similar to netcat and this concerns me most. The other tool is a remote webserver for measure internet speed > Do the speeds go up when you used a Cat5e cable at full duplex? The PC which is wired doesn't have those problems since I can transmit data from my remote office machine at the highest possble rate which is specified by my internet provider. > > Have you scanned for access points to be absolutely sure that there > are no > other wireless devices, or APs? > > Do you use encryption? Yes, but since I do get optimal performance "some time" I don't think this matters. > > What frequency and channel are you on and have you tried to change > channel/frequency? (some domestic devices like cordless phones, > wireless > earphones, bluetooth, microwaves, perimeter sensors, etc. can cause > co-channel > and adjacent channel interference and/or force sharing of the > bandwidth). > > Are both machines and the router's LAN on the same MTU? Sorry, what's "MTU" ? > > > > What tools and techniques can I use to debug this situation? > > > > Many thanks for a hint, > > First use ifconfig to see how many dropped packets you get on both > machines. > Then use iwconfig, or cat /proc/net/wireless on the PC running the > wireless to > see how many discarded packets you get, fragmentation, etc. as well > as nwid > packets from different networks on the same frequency. > > Then check with e.g. iptraf-ng what network connections are running, > their > rate(s) and if any of these should not be there. > > The router stats may also be revealing in this respect, as well as > dropped > packets on the WiFi. > > I hope the above will give something to work with, others may have > better > ideas and more specialised tools for troubleshooting this. Yes, that'll keep me busy a while. > > PS. I haven't mentioned spectrum analysers to keep this thread > within the > realm of quick fixes, but if you do have EM interference and the > source of it > is obscure, you may need more professional equipment to nail this > problem. > -- > Regards, > Mick Many, many thanks Mick, regards, Helmut.