From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.gmx.net (mout.gmx.net [212.227.15.15]) (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 B8E2B3B29D; Sun, 1 Dec 2019 14:03:43 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1575227014; bh=cmYuJ92UX2d9V/aKjkqSRoL5BcjXnWP8L+A8/kAondA=; h=X-UI-Sender-Class:Subject:From:In-Reply-To:Date:Cc:References:To; b=Pwhuya1w7WuuZnKBgWWMmb3grJrzE+52wsQXUm190LUXliG1pPeqFa1OlZZruzGZh wQypdkK3znauqNhCoc2fvrwtZDoOXlj34mcbKRV8Q0kNooWEnLnjk56k61SflrrFS0 GWudz4FjURTCBl5Ryf9vwjH8BZ22ZbDPjrgzcPY4= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from hms-beagle2.lan ([95.116.232.196]) by mail.gmx.com (mrgmx004 [212.227.17.190]) with ESMTPSA (Nemesis) id 1M7b6l-1ihGrz1TmH-0086Yk; Sun, 01 Dec 2019 20:03:34 +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: <349F14BC-683C-431E-BE8F-8574880F04B9@gmail.com> Date: Sun, 1 Dec 2019 20:03:33 +0100 Cc: Carsten Bormann , ECN-Sane , bloat Content-Transfer-Encoding: quoted-printable Message-Id: <337C951B-1812-4F20-89CE-F8B6BCF3B7C8@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> <02703449-D6CE-497D-BDBD-D79542D0EACF@gmx.de> <349F14BC-683C-431E-BE8F-8574880F04B9@gmail.com> To: Jonathan Morton X-Mailer: Apple Mail (2.3445.104.11) X-Provags-ID: V03:K1:mWjq3BN0uF7/3Lzz4cEb75P5sXoWOdVA1JaSQ9bhZ/Qf/cfqHzu kI/KCKzMQ4oSK/DeyQB3tXa17CuzxvstX6Z6555Pv9VGyEt63kTwdErkyFcRCBa32cplqcI I8loabb4qEsxAxG3b9yA71HstCvrCvf4LuPyQTrFoQTgjGt+g08BUXLxq4K2j313zXi2vHv 3mz7Vel3CMf1jc7cIXB1Q== X-Spam-Flag: NO X-UI-Out-Filterresults: notjunk:1;V03:K0:KWXQkgP5oIo=:RV09FCZE+bgzmrdDWQ3hYE R8C6h+UoEtIi/pjjqOKz2AclkDvFjlw6cwnLRe2IkDahuXsKs66/d52y51xpkSfSJXFYUI35/ +rbBG8T+ldI/saf40KGCsosaQ7bLEUlXsEEksMMqflOaBKsV0kXNpMV32jPaQ0AvzrbjvMQgi 0I4q+9Xon+dylcGZqgyofHdpWljP8ffilpKRW8jbP4po+eOjgzj7Qz4lrLJ3AR0nwHScKF7vP N1Pnxvix9uednAxHqpAmCj5mIfia5NtHgGdvGVRKGncPObVAGZWD2hlMBu6ZUUbyKg22hvIyI crFG49MLsbVyRcv0aMLLabVrgQ8y1CYP8fa4fQUOVJvjrC2HdRAbseKE4Ubao153ltEtXBtml TtC+j+fuP5+Yi+DsMS3yMLlComQIBKhOhLhzwY9oUr372HHcKbe9ZMqf/BZBoyEQ0EL5TGgE2 XESPTkaDjkq8LhQT/6CcHQKBkpy7pbapv2zSw1Q7dcfQsy1xtrjhEd20qIxA8sMgtngeNYenY EShwBIwQ/RWm85Tqz5KbsNbd2yXrsBkTD+8bnewgEnylLDmRhG0tlDTy4xBt6fIpS4Ih7JmMJ g/RlCx3WLYEjcLsrMg0V5lF+UiKHVVsJ+uxEBX0M4loEoY2j5uCCiJ78yJCG2ANM8OsE67hiZ HoU7te8zq+TVByTwpOtHQYe0JCifLNqR8slUkrn98UAfL0hIxTkmTyZ4rC2c+Efg6QY6WhhuD fYfoMfxM5ekTiMGNb5UgX2EPrZRmta5g8FalbKK5BHAalzk2NbeA57n/6BS6qzZw2XFrFXqBd zPNIdFlyqxIa+73N5lUfNkUo5dX49AwaTJeoUkYdLISB+qz/GN3CaHJwohBdM2KkwdyZDLwKh GfL1IFurautXkkNEf0+E+oEi0qBCvEivh9QJjoB8qIZkRbGeKobinLJC4kWylxM6mejKHsIBr 9N0vR2MYtkEG3qSWlUeIDyNGCULTPEe3pM+OezMwa9APjOW+e3QjuxDtKlgT9fEY04XQn5C1p tM8ySzJaI/NPFWXZVVlDb2tmTemETHkIW0SuJj+47p+DrdN6mNKKH+QBYm/VqQ+STeTO4CJgi bxoIlAg/0NHlj2zja6WenpA75P3qo8XWZrp6X9noK+vU54+tFzLYrwaA2Tkv1C4m8G29JtoY2 +J0V5j1H07YdrxJuZQjCN6+zrlqNIGrqriyVpzXS0GbK9qsJumlnTeo5eZG+mIgBJgDdC9Rl5 i/RhXIA/LwPlWMJ3ecQQXgVCT4qMqIR7Ro9K/8VEVBg5z4OumC7PUgQoHG5o= 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 19:03:44 -0000 Hi Jonathan, > On Dec 1, 2019, at 17:54, Jonathan Morton = wrote: >=20 >> On 1 Dec, 2019, at 6:35 pm, Sebastian Moeller = wrote: >>=20 >> 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 ). >=20 > Sure, we did think of several schemes that used a counter. But when = it came down to actually implementing it, we decided to try the simplest = possible solution first and see how well it worked in practice. =20 +1; simplicity has its own elegance. > It turned out to work very well, and can recover cleanly from as much = as 100% relative feedback error caused by ack loss: >=20 > If less feedback is observed by the sender than intended by the AQM, = growth will continue and the AQM will increase its marking to = compensate, ultimately resorting to a CE mark. =20 Well, that seems undesirable? > This is, incidentally, exactly what happens if the receiver *or* = sender are completely SCE-ignorant, and looks very much like RFC-3168 = behaviour, which is entirely intentional. >=20 > If feedback is systematically doubled by the time it reaches the = sender, perhaps through faulty ack filtering on the return path, it will = back off more than intended, the bottleneck queue will empty, and AQM = feedback will consequently reduce or cease entirely. Only a very = serious fault would re-inject ESCE feedback once SCE marking has = completely ceased, so the sender will then grow back towards the correct = cwnd after a relatively small negative excursion. Am I right to assume that the fault tolerance requires a = relative steady ACK stream though? >=20 > The above represents both extremes of 100% relative error in the = feedback, which is shown to be safe and reasonably tolerable. Great that the current simple scheme is safe (and for my pie in = the sky "let's high-jack the URG pointer" scheme essential, since there = are valid existimg users of the URG mechanism, at least google tells me = that both ftp and telnet are candidates; bit seem rare enough though = that giving these 16+1 bits something else to do might be fun). > Smaller errors due to random ack loss are more likely, and = consequently easier to tolerate in a closed negative-feedback control = loop. Fair enough. Best Regards Sebastian >=20 > - Jonathan Morton