From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from omr1.cc.vt.edu (omr1.cc.ipv6.vt.edu [IPv6:2001:468:c80:2105:0:2fc:76e3:30de]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by huchra.bufferbloat.net (Postfix) with ESMTPS id D3D7421F5FA for ; Fri, 25 Jul 2014 11:37:43 -0700 (PDT) Received: from mr4.cc.vt.edu (mr4.cc.vt.edu [198.82.164.236] (may be forged)) by omr1.cc.vt.edu (8.14.4/8.14.4) with ESMTP id s6PIbf2C017258; Fri, 25 Jul 2014 14:37:41 -0400 Received: from auth1.smtp.vt.edu (auth1.smtp.vt.edu [198.82.161.152] (may be forged)) by mr4.cc.vt.edu (8.14.4/8.14.4) with ESMTP id s6PIbZr8004275; Fri, 25 Jul 2014 14:37:40 -0400 Received: from turing-police.cc.vt.edu ([IPv6:2001:468:c80:2103:1178:9af6:f669:3164]) (authenticated bits=0) by auth1.smtp.vt.edu (8.14.4/8.14.4) with ESMTP id s6PIbY1D009723 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=NO); Fri, 25 Jul 2014 14:37:34 -0400 X-Mailer: exmh version 2.8.0 04/21/2012 with nmh-1.6+dev To: "R." In-Reply-To: Your message of "Sat, 24 May 2014 10:02:53 -0400." From: Valdis.Kletnieks@vt.edu References: Mime-Version: 1.0 Content-Type: multipart/signed; boundary="==_Exmh_1406313454_2052P"; micalg=pgp-sha1; protocol="application/pgp-signature" Content-Transfer-Encoding: 7bit Date: Fri, 25 Jul 2014 14:37:34 -0400 Message-ID: <13144.1406313454@turing-police.cc.vt.edu> X-Spam-Status: No, score=-0.0 required=5.0 tests=RP_MATCHES_RCVD autolearn=disabled version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mr4.cc.vt.edu Cc: cerowrt-devel@lists.bufferbloat.net Subject: Re: [Cerowrt-devel] Ideas on how to simplify and popularize bufferbloat control for consideration. X-BeenThere: cerowrt-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: Development issues regarding the cerowrt test router project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 25 Jul 2014 18:37:44 -0000 --==_Exmh_1406313454_2052P Content-Type: text/plain; charset=us-ascii On Sat, 24 May 2014 10:02:53 -0400, "R." said: > Further, this function could be auto-scheduled or made enabled on > router boot up. Yeah, if such a thing worked, it would be good. (Note in the following that a big part of my *JOB* is doing "What could possibly go wrong?" analysis on mission-critical systems, which tends to color my viewpoint on projects. I still think the basic concept is good, just difficult to do, and am listing the obvious challenges for anybody brave enough to tackle it... :) > I must be missing something important which prevents this. What is it? There's a few biggies. The first is what the linux-kernel calls -ENOPATCH - nobody's written the code. The second is you need an upstream target someplace to test against. You need to deal with both the "server is unavalailable due to a backhoe incident 2 time zones away" problem (which isn't *that* hard, just default to Something Not Obviously Bad(TM), and "server is slashdotted" (whci is a bit harder to deal with. Remember that there's some really odd corner cases to worry about - for instance, if there's a power failure in a town, then when the electric company restores power you're going to have every cerowrt box hit the server within a few seconds - all over the same uplink most likely. No good data can result from that... (Holy crap, it's been almost 3 decades since I first saw a Sun 3/280 server tank because 12 Sun 3/50s all rebooted over the network at once when building power was restored). And if you're in Izbekistan and the closest server netwise is at 60 Hudson, the analysis to compute the correct values becomes.... interesting. Dealing with non-obvious error conditions is also a challenge - a router may only boot once every few months. And if you happen to be booting just as a BGP routing flap is causing your traffic to take a vastly suboptimal path, you may end up encoding a vastly inaccurate setting and have it stuck there, causing suckage for non-obvious reasons for the non-technical, so you really don't want to enable auto-tuning unless you also have a good plan for auto-*RE*tuning.... --==_Exmh_1406313454_2052P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 Comment: Exmh version 2.5 07/13/2001 iQIVAwUBU9Kj7gdmEQWDXROgAQJ08xAAnN4GFvlxFPdnUuLnbeE9HzaRlpKC1qab YeHi134/T2dhTh8O0aCeeGGgFO3oi4wCsUOz25uvN9tPxu8c2LEs6tFLLnUGn4io oXrkRNWBwNg4WZNqeMc2vNQP2yTN6entW0HosLArWY8DSDQV5Otk0nAQpuAvi64E h8/kSh/dT5GCGCFFj7N1RNYzqLxvW/fWLKeaORyAlLWTCH3FiryYZZAussQJ+52E Uf/C5lYxyqI8ZOoJjmhbWqMWyvL/B3J+r/BKFtLgXXS9R5DWYaF7mw49VAtDMHJR u/ybsPdDT1z9ky0TvKxFGlwLhm9pH6MKDPoHPPk5SWs63K08kkj2ro8ims1zFy/r xSgC/TsHvMRzl74/oLeFtFw/SDn+uhIdq+0TZM2GltjCCKt7vbDl65EbCA2gHc2h KC2MD8IlA+dw7ERgniovVOmBv1Ke9hnsOlOVV/VdxLw9H0Yem09clc7CaFeZNaqq 32Tue2u9wF48s2FD8VAGfd7BhEBh2YhLIyKWgnbtiMcaowmeJPj+jlKEVid4msw5 kasIgf6srV0V3qFkYiLZyLTkC5TPBNDiG/dp3Foe85pJcsxo84Ein126pX3dpwJc Xgp5cP1MP53Py/9kEdCXKrgCNQzc5V8f+0Qqv5oL/JrmJqcyeyrIWRt43qWHXGGW eep0uof30dQ= =fZEq -----END PGP SIGNATURE----- --==_Exmh_1406313454_2052P--