From owner-freebsd-net@FreeBSD.ORG Wed Nov 30 12:51:47 2011 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id C0FE41065673 for ; Wed, 30 Nov 2011 12:51:47 +0000 (UTC) (envelope-from hapvbk@yahoo.co.uk) Received: from nm5.bullet.mail.ukl.yahoo.com (nm5.bullet.mail.ukl.yahoo.com [217.146.182.226]) by mx1.freebsd.org (Postfix) with SMTP id F11F48FC1A for ; Wed, 30 Nov 2011 12:51:46 +0000 (UTC) Received: from [217.146.183.213] by nm5.bullet.mail.ukl.yahoo.com with NNFMP; 30 Nov 2011 12:38:02 -0000 Received: from [77.238.184.61] by tm6.bullet.mail.ukl.yahoo.com with NNFMP; 30 Nov 2011 12:38:02 -0000 Received: from [127.0.0.1] by smtp130.mail.ukl.yahoo.com with NNFMP; 30 Nov 2011 12:38:02 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.co.uk; s=s1024; t=1322656682; bh=q9Oq0qfyaCT8GNe2HFrfxY44k2wZiARqsi8R+BtoSmo=; h=X-Yahoo-Newman-Id:X-Yahoo-Newman-Property:X-YMail-OSG:X-Yahoo-SMTP:Received:Message-ID:From:To:Subject:Date:MIME-Version:Content-Type:X-Priority:X-MSMail-Priority:Importance:X-Mailer:X-MimeOLE; b=BAnWCDft75IRflEZvyWvO1Y65UX/96j4cNtfzpFnE9jHmBZLOofntQsh+BF+upbqEDYM7js6Q9ahjglfOkPzjKA0rWB2fsQXt1bg4wShv0fwoDHsAWZMR4W/gTPDXIuZuugZ9YXdTTEZon2TLXcxbXzJQSovTOS9Bi1fcdM5zIc= X-Yahoo-Newman-Id: 130386.68567.bm@smtp130.mail.ukl.yahoo.com X-Yahoo-Newman-Property: ymail-3 X-YMail-OSG: Aj93peMVM1muAfeQYXgotbgkXw.SLAfmYzFb4.47RxJq7qa Vy5t_CdB68m32W_n86yg9wzN1fd19wCXkA2Lg7GQwwMQPNu4sxspPMYQ0IGn 9_bXIFYtnDGdCx4MLmhbIpw3fnuoknC7B1pBKBpyZNcZ9SwK8mmtXbMX8V_U 5OHvcK4St._wZ8uGPfHr_AndQiaOe.sC4u_FHfyUFT_vKS1s_1hbURzwLMxk mwP3RhDrZ8KsLdvKvjbjcl2Ycc6UCGfgBBv_LD96D2jc0_9hsbdnhoVI9zDH l7Xlv.G_rqADrLQdbdr7B5PTZ3EUAM9PY0nxFgfA10wee76ewkOFqIh_fdeW 5JiSOgfFEbseOMJN1rCBiW4gHIcZeHTIvBikMNkc- X-Yahoo-SMTP: xBpCc9iswBApASleyiIs9lcZMA-- Received: from PC (hapvbk@66.11.191.2 with login) by smtp130.mail.ukl.yahoo.com with SMTP; 30 Nov 2011 12:38:01 +0000 GMT Message-ID: <69C75F6ECC9646C79374299EDF0E4304@PC> From: "Viet-Ha Pham" To: Date: Wed, 30 Nov 2011 07:37:48 -0500 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 15.4.3538.513 X-MimeOLE: Produced By Microsoft MimeOLE V15.4.3538.513 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Subject: Wifi throughput test issue (FreeBSD 8.2) X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 30 Nov 2011 12:51:47 -0000 Hello, I am doing some throughput measurement for Wifi network. I am using = jperf/iperf to generate traffic (at the transmitter) and measure the = throughput (at the receiver). The transmitter and receiver are running = FreeBSD 8.2, using CM9-GP as the Wifi NIC. We are testing AWGN channel. = So, the transmitter and receiver are connected by cables, txpower on = both sides is set lower than the max (ranging from 0 to 10), AWGN noise = is injected in the middle of the cable.=20 We measure the maximum throughput at each transmission rate. Transmitter = is a STA, receiver is an AP. We fix the unicast rate at the transmitter = to 54 Mbps (using "ifconfig ... ucastrate" command). The packet size is = set to 400 Bytes, UDP protocol is used and the transmit bandwidth is set = to 30 Mbps in order to flood the transmission channel (to push it to its = limit). At first, at the receiver (AP) the measured throughput is about = 12 Mbps. Then I fix the unicast rate at the receiver (using ifconfig = again) to 54 Mbps. The measured throughput increases to 20 Mbps. I set = the unicast rate at the receiver to autoselect again, the throughput is = still 20 Mbps.=20 When I switch the rate at the receiver, there are multiple message = displayed on the screen of the transmitter: "wlan0: = ieee80211_new_state_locked: pending RUN -> AUTH transition lost". This = message is repeated for many times (at least 20).=20 I repeated the test with all transmission rates, change the packet size = and still observe the same thing: a throughput improvement of about 30% = is observed when I switch the unicast rate at the receiver and the = improvement is still there when I switch the unicast rate back to = autoselect. The same thing is observed in modes a and g. The same thing = is observed if the unicast rate at the receiver is set different from = the unicast rate at the transmitter.=20 I spent time to look at the kernel source codes but I did not find a = solid answer for this. Please help me to identify the problem and the = answer.=20 My question is:=20 1. Why do I have that throughput improvement when I switch the rate like = that?=20 2. Is it a bug in the driver?=20 3. What does the error/infor message on the transmitter mean?=20 Thank you so much.=20 HAPV