From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from server.irh.it (server.irh.it [109.74.199.9]) by huchra.bufferbloat.net (Postfix) with ESMTP id D49A4200762 for ; Sat, 10 Mar 2012 02:31:18 -0800 (PST) Date: Sat, 10 Mar 2012 11:30:06 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=irh.it; s=dkim_3; t=1331375414; bh=LIogg0CWmcTM0AU+/2KLDbjLKNb6esZVZFRgLrytsvg=; h=From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Transfer-Encoding:In-Reply-To; b=Z+UqpDSanZTv0AY4RDGcFD8TW2B8XJb8OhKij6KfwVkMoYHAuHtoFI24LFjNQA4uM To33UhppQeEmAuNLYDGomUAWP4kK7fGajwJQlG4D80mM7UrsafJKF3zs30k/Fj7jbM 05On2HqLLAAgT8RgNT/7jzQLwzzEf0s3nj2JJEkI= From: Davide Gerhard To: Dave Taht Message-ID: <20120310103006.GA3074@paperino> References: <20120309215037.GI2539@paperino> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Face: %QFZ"7Mn450zJnOdW; Bz&@BS6LX'KE+9 Subject: Re: [Bloat] troubles with congestion (tbf vs htb) X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 10 Mar 2012 10:31:19 -0000 =- Dave Taht wrote on Fri 9.Mar'12 at 14:08:55 -0800 -= > Dear Davide: thank you for the answer. > > sounds like a job for the bloat list. I note your attachment got > filtered out on your > posting to netdev. yes. In any case, the description is enough good to understand the problem (i hope). > > None of what you describe surprises me, but I would love to duplicate > your tests, exactly, against the new 3.3 kernel, which has BQL and > various active AQMs, and I also remember various things > around ssthresh being fiddled with over the past year. Like you suggested, I will try with 3.3.0-rc6 (next week). In the meantime I want to deepen the argument, because I have read some papers, from this[0] page, and from others[1][2] but I didn't understood how can I use these changes. In the sense that, all changes is it embedded into the kernel and I will use the same tc rules or I need to change something? (CONFIG_BQL, ...) Moreover, have you some suggestions about the test environment and the commands that I used? thanks /davide [0] http://www.phoronix.com/scan.php?page=news_item&px=MTAzODg [1] http://lwn.net/Articles/469652/ [2] http://lwn.net/Articles/454378/ > > On Fri, Mar 9, 2012 at 1:50 PM, Davide Gerhard wrote: > > Hi, > > I am a master's student from the university of Trento, I have been doing a > > project, for the course of advanced networking (In a group of 2), focused > > on the TCP congestion control. I used tc with htb to simulate a link with > > 10mbit/s using a 100mbit/s real ethernet lan. Here is the code I used: > > > > tc qdisc add dev $INTF root handle 1: netem $DELAY $LOSS $DUPLICATE > >  $CORRUPT $REORDENING > > tc qdisc add dev $INTF parent 1:1 handle 10: htb default 1 r2q 10 > > tc class add dev $INTF parent 10: classid 0:1 htb rate ${BANDW}kbit ceil > >  ${BANDW}kbit > > > > and here is the topology > > > > client -->|    |--> server with iperf -s > >          |    | > >          |    | > >          +    + > >           eth0 > >    CONGESTION machine > > > > The congestion machine have the following configurations: > > - kernel 3.0 > > - echo 1 > /proc/sys/net/ipv4/ip_forward > > - echo 0 > /proc/sys/net/ipv4/conf/default/send_redirects > > - echo 0 > /proc/sys/net/ipv4/conf/all/send_redirects > > - echo 1 > /proc/sys/net/ipv4/ip_no_pmtu_disc > > - echo 0 > /proc/sys/net/ipv4/conf/eth0/send_redirects > > > > The client captures the window size and ssthresh with tcp_flow_spy but we do > > not see any changes in the ssthresh and the window size is too large > > compared to the bandwidth*latency product (see attachment). In a normal scenario, > > this would be acceptable (I guess), but in order to obtain some relevant > > results for our work, we need to avoid this "buffer" and to activate > > the ssthresh. I have already tried to change backlog but this does > > not change anything. I have also tried to use tbf with the following command: > > > > tc qdisc add dev $INTF parent 1:1 handle 10: ftb rate ${BANDW}kbit burst 10kb > >  latency 1.2ms minburst 1540 > > > > In this case, the congestion works correctly as we expect, but if we use > > netem I have to recalculate again all the needed values (correct?). Are there > > any other solutions? > > > > Best regards. > > /davide > > > > P.S Here follows the sysctl parameters used in the client: > > net.ipv4.tcp_no_metrics_save=1 > > net.ipv4.tcp_sack=1 > > net.ipv4.tcp_dsack=1 > > > > -- > > "The abdomen, the chest, and the brain will forever be shut from the intrusion > > of the wise and humane surgeon." - Sir John Eric Ericksen, British surgeon, > > appointed Surgeon-Extraordinary to Queen Victoria 1873 > > -- > > To unsubscribe from this list: send the line "unsubscribe netdev" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at  http://vger.kernel.org/majordomo-info.html > > > > -- > Dave Täht > SKYPE: davetaht > US Tel: 1-239-829-5608 > http://www.bufferbloat.net -- "Man will never reach the moon regardless of all future scientific advances." - Dr. Lee DeForest, "Father of Radio & Grandfather of Television"