From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.gmx.net (mout.gmx.net [212.227.17.21]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id E70273B29D; Sun, 1 Dec 2019 11:35:59 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1575218150; bh=FQZncLKbqBhCGTaj3dzDPv4KHRbE5eHJM8QMGJl2gXs=; h=X-UI-Sender-Class:Subject:From:In-Reply-To:Date:Cc:References:To; b=IccAQEmetN2NfmTrM9BkyeAVsY9qJil4r6dKnp62loX8zRMioIj1fu0sctxs7dApq GiHq/KG1PDbnAjKZLrJ0pTBbU8RKPv8QBGDzzQqcwu6ZfbaQVAIZdK2x7ZexxqtsUl wQvnQVnFeK0swDMwzXoVZSoi055w6oopzBZbZogc= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from hms-beagle2.lan ([95.116.232.196]) by mail.gmx.com (mrgmx104 [212.227.17.168]) with ESMTPSA (Nemesis) id 1N49lJ-1hbL9T3M2b-0105eF; Sun, 01 Dec 2019 17:35:50 +0100 Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.11\)) From: Sebastian Moeller In-Reply-To: <8C5FD2CE-D24F-4998-A636-8F85279C67BA@gmail.com> Date: Sun, 1 Dec 2019 17:35:49 +0100 Cc: Carsten Bormann , ECN-Sane , bloat Content-Transfer-Encoding: quoted-printable Message-Id: <02703449-D6CE-497D-BDBD-D79542D0EACF@gmx.de> References: <63E9C0E4-C913-4B2F-8AFC-64E12489BC65@gmail.com> <297503679.4519449.1575069001960@mail.yahoo.com> <54C976BC-DEC7-4710-9CFF-0243559D9002@gmail.com> <156EA284-C01D-4FAA-89F4-DB448795F7FC@gmx.de> <385CF47C-17AD-4A62-9924-068E1485FFD5@gmail.com> <8C5FD2CE-D24F-4998-A636-8F85279C67BA@gmail.com> To: Jonathan Morton X-Mailer: Apple Mail (2.3445.104.11) X-Provags-ID: V03:K1:g1cj1cHNAxDFlY/bQpy3+YX4SWBki/OAGHxfw6M5ZoCHYfcO9MG LAL4Pti0D6zaUzXFk6V3BHq6moCSqTtJLLI0W1iC5lexwWuaE71vpHif22DJOAR4cmSMGbH P0d3oxIbKcN1/0IWDN7NO/3zQnG1rBdyIZjfC2mIvitSGHMPSN1mwdYWumvLVOzeRPNY/sz EYNMYtYTcAn8UF5ropIyg== X-Spam-Flag: NO X-UI-Out-Filterresults: notjunk:1;V03:K0:SLIm0HvsgKE=:RpIvYvl1WzrtPYRzrXlv6h qzwI9far/u3Fmauvrox/u2b/WU3iwpWEnvmLEBTwdRWgxplH+l1inQRvIEsEF9TXYrghq79ur V7xNoFGA/maw5XB9ILNCQ7Kmpx4BVbG/AEpTT8o0Rs6qFg3lzGRr+rBEvCMCmYY2VLhFdpwKF Vak1ZdX1d6rxnqWmCZXBzQk4vKajrmbM7SCvFDW9SZKsn3llmScpizYzYFyhzuZLvVp+NRRx2 pmRteUHcxoUaHeMkTdnUWao8jhn2TXlOv5MvXAjLh/5OwgfmkTin5FsOQ5OnVUpEKxlI6rghD j521joouFH8u37Kgv6ZIN/TrtO7xBzaBJCPwuShPcYlKOJhhGJVXWnaOvCKhdlJzBcIuTXAgz p5fNIg54E8VnN3icQhSD6yxoz0VK96XfLb4cNWx2QuizJges8Qs6iFU3TpYdCANmurbSlEpAV Q7WG3OCOBzo1dOK2T/nLRZalxhBKhMwuRgWYSNU6CouivwLv7vAaDeNiaDqEOZ3OuLPTIHVxm Tiye62iZRtfeYT1a01LGdzSh9YgvSnaOSKtoKpzJggk8KAVtPGAa2v+HhOjiOJzIMI7jtm2Qi ZzndwcY6l6MpSg9ljNxUo4WOrrUQPcZhwQ8cPhiOhj1gee2eERSgKLz4iXQNNyEBZntiW1qsC bFBmZoj5GfBLu5RpcUX4Lq6Yt7FzBw1exINJ3qvceVFCLl7zXZdh2aLPYL+OxYMfTG3QHv/Ji /Ti1/tIeuxkzBgUaQFLyR/NMhXLgmG0SEHRyWHfAFOTIpBibkM7y9/78GQtLKRnC6EZ+0cfyg 1iMFlhMmcnlWWpzRE1YwI60Q/T2LZJWiP+kC8pxhwAJ1E/QCY2andgjB4RVw9khEHOijp61Si PjJU8Xcvoq6UmHFZhr5vxSe7ObnDX31jXolU2O8byUvTo/ZBJQJgzhTXJ2XhY9IrcqqtrrnWr qhF4iAisrhFPHy/20FntQElV+reDPKyYSFu9WqUTFHND7VuL/CsVw0BuhuwrrfJ2SJmbo15Q2 agsLG/CWtWOg8Sam+RLlOSDjr6QAiGyNOG+fRlPOUzykdOuno92pUKm14peuCiI7jCdKsgBfg dXc6QT0bs5XTIRjpq9TBQzz5JmpGQDr4+/9/qkGDeO22CW4YaOhHG/DkyxmWE/HXLwfPMXZtB kT/25Wgp7stJ4IqOgJc2TEaRSL81Ox3Jom9K2GQiWFSgPqNgIS2aOG/YSnbJGZSELStch2YDY fzQI/wGt0xJJFvw9CVQ0a5IbYdO1o0AZEJ+0dTw== Subject: Re: [Ecn-sane] [Bloat] sce materials from ietf X-BeenThere: ecn-sane@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Discussion of explicit congestion notification's impact on the Internet List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 01 Dec 2019 16:36:00 -0000 Hi Jonathan, > On Nov 30, 2019, at 23:23, Jonathan Morton = wrote: >=20 >> On 1 Dec, 2019, at 12:17 am, Carsten Bormann wrote: >>=20 >>> There are unfortunate problems with introducing new TCP options, in = that some overzealous firewalls block traffic which uses them. This = would be a deployment hazard for SCE, which merely using a spare header = flag avoids. So instead we are still planning to use the spare bit - = which happens to be one that AccECN also uses, but AccECN negotiates in = such a way that SCE can safely use it even with an AccECN capable = partner. >>=20 >> This got me curious: Do you have any evidence that firewalls are = friendlier to new flags than to new options? >=20 > Mirja Kuhlewind said as much during the TCPM session we attended, and = she ought to know. There appear to have been several studies performed = on this subject; reserved TCP flags tend to get ignored pretty well, but = unknown TCP options tend to get either stripped or blocked. >=20 > This influenced the design of AccECN as well; in an early version it = would have used only a TCP option and left the TCP flags alone. When it = was found that firewalls would often interfere with this, the three-bit = field in the TCP flags area was cooked up. Belt and suspenders, eh? But realistically, the idea of using an = accumulating SCE counter to allow for a lossy reverse ACK path seems = sort of okay (after all TCP relies on the same, so there would be a nice = symmetry ). I really wonder whether SCE could not, in addition to its current bit, = borrow the URG pointer field in cases when it is not used, or not fully = used (if the MSS is smaller than 64K there might be a few bits leftover, = with an MTU < 2000 I would expect that ~5 bits might still be usable in = that rate case). I might be completely of to lunch here, but boy a nice = rarely used contiguous 16bit field in the TCP header, what kind of = mischief one could arrange with that ;) Looking at the AccECN draft, I = see that my idea is not terribly original... But, hey for SCE having an = additional higher fidelity SCE counter might be a nice addition, = assuming URG(0), urgent pointer > 0 will not bleached/rejected by = uninitiated TCP stacks/middleboxes... Best Regards Sebastian >=20 > - Jonathan Morton >=20