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[37.33.7.26]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-543ebebecc3sm783607e87.242.2025.02.01.09.26.27 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sat, 01 Feb 2025 09:26:29 -0800 (PST) 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: <48FB68A5-8320-4B46-97E1-4C67BB7B7B1B@gmx.de> Date: Sat, 1 Feb 2025 19:26:27 +0200 Cc: =?utf-8?Q?Dave_T=C3=A4ht?= , David Collier-Brown , Rich Brown via Bloat Content-Transfer-Encoding: quoted-printable Message-Id: <4B1379B8-7EF6-4D34-8091-451A48585811@gmail.com> References: <48F77C27-0E57-4F96-9BD8-238CC93342F8@gmail.com> <9A110AF4-E976-4228-9FA6-92C5C99F611A@gmx.de> <48FB68A5-8320-4B46-97E1-4C67BB7B7B1B@gmx.de> To: Sebastian Moeller X-Mailer: Apple Mail (2.3654.100.0.2.22) Subject: Re: [Bloat] Comcast & L4S X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 01 Feb 2025 17:26:32 -0000 > On 1 Feb, 2025, at 7:06 pm, Sebastian Moeller wrote: >=20 >> As with NQB, Cake already does essentially what L4S requires, except = for default-configured Codel being less than ideal as an AQM for = producing congestion signals for a DCTCP-type response. I have no = intention of modifying Cake to *specifically* accommodate L4S in any = way. If their crap doesn't work properly in a standards-compliant = environment, that's THEIR problem. >=20 > Now, as advocatus diabolical, the way CoDel works we have interval = and/or target as configurable parameters and a trade-off between = maintaining utilisation over the wider internet and keeping the = signalling reactive for closer by flows, maybe we could teach cake to = allow a second set of interval/(automatically calculated) target to = optimise for local and non local traffic, and use a proper (configurable = and maskable) DSCP/TOS to steer packets into this? Maybe CS7 would do to = signal its intent for local delivery? Codel's default 5ms target is already pretty tight, about as tight as = you can reasonably make it while still accommodating typical levels of = link-level jitter. And COBALT does already find and maintain the = appropriate marking rate for DCTCP when required - it just takes a = little while to ramp up, so there is a noticeable hump in the delay = curve during flow startup. I don't see any low-hanging fruit there; = Codel is simply not designed for that congestion response style. DelTiC is a bit more flexible in this respect. I don't however plan to = add DelTiC to Cake. Rather, I'm building a new qdisc that does some of = the same things as Cake, but using more advanced technology and = generally learning some object lessons from the experience. - Jonathan Morton=