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[37.136.162.179]) by smtp.gmail.com with ESMTPSA id 38308e7fff4ca-2ec05c05f8asm5224951fa.41.2024.06.14.04.05.45 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 14 Jun 2024 04:05:45 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.100.0.2.22\)) From: Jonathan Morton In-Reply-To: Date: Fri, 14 Jun 2024 14:05:43 +0300 Cc: Cake List Content-Transfer-Encoding: quoted-printable Message-Id: <2B93218F-F3EF-4A79-9061-A1A3AB922CE6@gmail.com> References: To: Dave Taht X-Mailer: Apple Mail (2.3654.100.0.2.22) Subject: Re: [Cake] cobalt, compared X-BeenThere: cake@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Cake - FQ_codel the next generation List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 14 Jun 2024 11:05:48 -0000 > On 14 Jun, 2024, at 2:40 am, Dave Taht via Cake = wrote: >=20 > = https://www.tu-ilmenau.de/fileadmin/Bereiche/IA/vsbs/Publikationen/2024/SS= K_NOMS24_AdaptiveAQM_Authors-version.pdf I don't understand their test methodology. I mean that literally. Their results indicate queue delays in the region of one whole second. = This is wildly different from the target delays of any of the AQMs = tested. In fact, their results for COBALT are above the trigger for = BLUE activity (which they also helpfully listed in their configuration = table). One obvious conclusion is that COBALT's lower queue delays and = higher loss rates in their results are precisely due to relying on the = BLUE component. But that is most certainly not the intended operating = regime for COBALT - BLUE is provided as a failsafe, not as a primary = congestion signalling mechanism. They state a link rate of 2Gbps, and a variety of flow rates, the = highest of which is 10Mbps. Even if we multiply the latter by the = number of clients (100), the 2Gbps link is not saturated. If there's a = separate flow between each client-server Cartesian product, and the = clients are each limited to a 10Mbps link with its own AQM instance, = then we should expect AQM activity to be capable of keeping the queue = delay down to about 20ms (5x a small number of MTUs), which is 50x = better than their typical reported results. I can only conclude that, for whatever reason, they have constructed a = traffic scenario (the details of which are not adequately reported in = the paper) which induces an extreme level of congestion, which of course = the conventional AQMs have some trouble with handling (but COBALT does = better on, due to BLUE activity). They then introduce their own AQMs to = this scenario, and report that they do better on a couple of metrics = (but are still very bad on the others). Overall, this paper does not provide any information of interest. - Jonathan Morton=