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[173.246.8.242]) by smtp.gmail.com with ESMTPSA id t2sm22151989qth.33.2019.07.21.09.00.30 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 21 Jul 2019 09:00:31 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 11.5 \(3445.9.1\)) From: Jonathan Morton In-Reply-To: <22af0671-fdd0-0953-fc96-55b34beb0be9@bobbriscoe.net> Date: Sun, 21 Jul 2019 12:00:30 -0400 Cc: Sebastian Moeller , "De Schepper, Koen (Nokia - BE/Antwerp)" , "Black, David" , "ecn-sane@lists.bufferbloat.net" , "tsvwg@ietf.org" , Dave Taht Content-Transfer-Encoding: quoted-printable Message-Id: References: <364514D5-07F2-4388-A2CD-35ED1AE38405@akamai.com> <1238A446-6E05-4A55-8B3B-878C8F39FC75@gmail.com> <17B33B39-D25A-432C-9037-3A4835CCC0E1@gmail.com> <52F85CFC-B7CF-4C7A-88B8-AE0879B3CCFE@gmail.com> <87ef2myqzv.fsf@taht.net> <803D9CA8-220E-4F98-9B8E-6CE2916C3100@gmail.com> <0079BC6B-4792-48ED-90D3-D9A69407F316@gmx.de> <22af0671-fdd0-0953-fc96-55b34beb0be9@bobbriscoe.net> To: Bob Briscoe X-Mailer: Apple Mail (2.3445.9.1) Subject: Re: [Ecn-sane] [tsvwg] Comments on L4S drafts 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, 21 Jul 2019 16:00:32 -0000 > On 21 Jul, 2019, at 7:53 am, Bob Briscoe wrote: >=20 > Both teams brought their testbeds, and as of yesterday evening, Koen = and Pete Heist had put the two together and started the tests Jonathan = proposed. Usual problems: latest Linux kernel being used has introduced = a bug, so need to wind back. But progressing. >=20 > Nonetheless, altho it's included in the tests, I don't see the = particular concern with this 'Cake' scenario. How can "L4S flows crowd = out more reactive RFC3168 flows" in "an RFC3168-compliant FQ-AQM". = Whenever it would be happening, FQ would prevent it. >=20 > To ensure we're not continually being blown into the weeds, I thought = the /only/ concern was about RFC3168-compliant /single-queue/ AQMs. I drew up a list of five network topologies to test, each with the SCE = set of tests and tools, but using mostly L4S network components and = focused on L4S performance and robustness. 1: L4S sender -> L4S middlebox (bottleneck) -> L4S receiver. This is simply a sanity check to make sure the tools worked. Actually = we fell over even at this stage yesterday, because we discovered = problems in the system Bob and Koen had brought along to demo. These = may or may not be improved today; we'll see. 2: L4S sender -> FQ-AQM middlebox (bottleneck) -> L4S middlebox -> L4S = receiver. This is the most favourable-to-L4S topology that incorporates a non-L4S = component that we could easily come up with, and therefore . Apparently = the L4S folks are also relatively unfamiliar with Codel, which is now = the most widely deployed AQM in the world, and this would help to = validate that L4S transports respond reasonably to it. 3: L4S sender -> single-AQM middlebox (bottleneck) -> L4S middlebox -> = L4S receiver. This is the topology of most concern, and is obtained from topology 2 by = simply changing a parameter on our middlebox. 4: L4S sender -> ECT(1) mangler -> L4S middlebox (bottleneck) -> L4S = receiver. Exploring what happens if an adversary tries to game the system. We = could also try an ECT(0) mangler or a Not-ECT mangler, in the same = spirit. 5: L4S sender -> L4S middlebox (bottleneck 1) -> Dumb FIFO (bottleneck = 2) -> FQ-AQM middlebox (bottleneck 3) -> L4S receiver. This is Sebastian's scenario. We did have some discussion yesterday = about the propensity of existing senders to produce line-rate bursts = occasionally, and the way these bursts could collect in *all* of the = queues at successively decreasing bottlenecks. This is a test which = explores that scenario and measures its effects, and is highly relevant = to best consumer practice on today's Internet. Naturally, we have tried the equivalent of most of the above scenarios = on our SCE testbed already. The only one we haven't explicitly tried = out is #5; I think we'd need to use all of Pete's APUs plus at least one = of my machines to set it up, and we were too tired for that last night. - Jonathan Morton=