From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from exout103.netflix.com (exout103.netflix.com [69.53.237.162]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (Client CN "exout103.netflix.com", Issuer "CERTISSUER101" (not verified)) by huchra.bufferbloat.net (Postfix) with ESMTPS id E8E0121F15E for ; Fri, 30 Nov 2012 10:57:01 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; s=s2048;d=netflix.com; h=from:to:cc:subject:date:message-id:references:in-reply-to :content-type:mime-version; bh=S5F4dH52uJVNDSQEP2ghTL8ut5g=; b=C+po3Jz873ExSJAT3Wc2MMRWkIrPGSLIGZdOIzUkwelG8CDf8TVBASvhuCRwAQutJBQv2k/o 4/NXdmA/tO9T+A3lD1zkMVWpe+Xew65kTA6SGnTYnh6uTF5Q87LDMp82mvoMjIEEFxZ6LIaQ N23HgOh28cz+TAvfPJXhYnIQyR5q5TQIL/2XvaAGBlmanen0m4UGNxpTUoWEjBQc0nOxyH+7 XnGooBydppTtDuTKdMw24YGtvhfZ2brqhd0X0cY6x8NDdd/yZSrPQew4eZ9p1cAIPh/mTCj6 4Q3SI0c9T7LvMSPrMq1jW1Ep64klPTSG8YpjOpyUvozL+2QaO9w9qQ== DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s2048;d=netflix.com; h=from:to:cc:subject:date:message-id:references:in-reply-to :content-type:mime-version; b=gaBs0keILiAyqsjJNn7ptZneTdxHdnVNC/qScTh+0VdZzie+qfNUZC7+rB954GSH/bFtjBRt Z8lqyY8WxmCNSuCF1ZxP1YOUDvtl/CaVDpFbx5cYAnhoFewuZibvxChu1MymzXAUO50ZOYMC 0CyjsvU9OdzZx3pAgSKTJTt7NGawz4BkmyGMJBnlvqBj0Y9c7SCxhicpaaIRGrJmxa6S+154 Qvzv3DgSkr1YHmjQvhGy1vrl8JBqT9ivIaiodvG+2NqSOwNk+2Ox9vdd9GBnwSdr+hQNN/He EVSvTJlUwXnxAMZpbjT+5qoV33kZrUGpqm39QsrJHs12M91lAPotpw== Received: from EXFE104.corp.netflix.com (10.64.32.104) by exout103.netflix.com (10.64.240.73) with Microsoft SMTP Server (TLS) id 14.2.298.4; Fri, 30 Nov 2012 10:57:04 -0800 Received: from EXMB106.corp.netflix.com ([169.254.6.135]) by exfe104.corp.netflix.com ([10.64.32.104]) with mapi id 14.02.0283.003; Fri, 30 Nov 2012 10:57:00 -0800 From: Mark Watson To: "" Thread-Topic: [Bloat] Bufferbloat research: Help required Thread-Index: AQHNzEE8aAPk+Sdih0uSKdrIvyqyK5f/+3uAgANLEoA= Date: Fri, 30 Nov 2012 18:56:59 +0000 Message-ID: <15815375-7E44-42DE-AE49-6630A053B88B@netflix.com> References: In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.2.229.226] Content-Type: text/plain; charset="us-ascii" Content-ID: <04659E745BA2FD49930C3D4316509C6C@netflix.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Cc: "" , Dauran raza Subject: Re: [Bloat] Bufferbloat research: Help required 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: Fri, 30 Nov 2012 18:57:02 -0000 It's also interesting to note that cellular wireless systems have been desi= gned with a primary objective of reducing packet loss, at the expense of de= lay and especially delay variability introduced by link layer ARQ and other= schemes. This approach maximizes the throughput of a single long-lived TCP= connection, which is not an especially common traffic pattern. Furthermore, the throughput of a cellular wireless radio channel varies by = orders of magnitude on fairly rapidly (channel conditions are reassessed hu= ndreds of times per second): what was a reasonable sized buffer for the thr= oughput at one moment becomes a bloated one a fraction of a second later. Best, Mark Watson On Nov 28, 2012, at 8:39 AM, Dave Hart wrote: > On Sun, Nov 25, 2012 at 3:21 PM, Dauran raza wrot= e: >> My name is Dauran Raza and i am currently doing Masters in Computer Scie= nce >> from University Paderborn. Currently i am researching on the Problem of >> Bufferbloat for a course under Prof Holger Karl. I have been regularly >> reading you articles on your websites about this problem and it has been >> really helpfull. I have a problem which is not answered so far through a= ny >> research paper. I wanted to know is there any difference in Wired and >> Wireless networks caused by this problem and can you guide me with any g= ood >> paper or article to read on. >=20 > I wish you well in your graduate studies, and I commend Prof. Holger > Karl for his interest in the topic. I am, however, cautious that I > don't want to do your research for you. >=20 > Briefly, as you would hopefully anticipate, wireless presents more > challenges to addressing bufferbloat than wired. For example, the > jitter (delay variability) is much worse than wired, and 802.11n > requires aggregation of multiple packets into one transmission to > achieve its higher throughputs vs. 802.11g, which further increases > jitter and complicates AQM. >=20 > Even ignoring wireless, gigabit wired is more challenging than 100 > Mbit, again because techniques used to maximize peak throughput (such > as deeper transmit buffers and receive interrupt coalescing) tend to > make bufferbloat more of a challenge. >=20 > There's a theme here -- those developing network advancements have > tended to focus on maximizing achievable throughput without enough > consideration of the negative effects on bufferbloat, often (at least > historically) with no understanding of bufferbloat at all. >=20 > I pray I have not said too much already, and if I have, please convey > my apologies to Prof. Karl. >=20 > I suggest digging into the mailing list archives: >=20 > https://lists.bufferbloat.net/listinfo >=20 > I'd start with the bloat and bloat-devel lists, then the Codel-related > lists, and possibly other -devel and -commit lists. Also, if you make > yourself useful in one or more bufferbloat.net projects, you will gain > firsthand knowledge of the issues as well as personal relationships > with people well-versed in the issues. >=20 > Thanks for your interest, > Dave Hart > _______________________________________________ > Bloat mailing list > Bloat@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/bloat >=20