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-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id CE2E03B29D for ; Sat, 1 Feb 2025 13:05:11 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmx.de; s=s31663417; t=1738433110; x=1739037910; i=moeller0@gmx.de; bh=uUzXEkkYSrmVGuOuUn59D3iEHWedMhHZCt9EZVFODmI=; h=X-UI-Sender-Class:Content-Type:Mime-Version:Subject:From: In-Reply-To:Date:Cc:Content-Transfer-Encoding:Message-Id: References:To:cc:content-transfer-encoding:content-type:date:from: message-id:mime-version:reply-to:subject:to; b=RlN58yUa72PiCpPuQqMSXSdQml6C+TIKn0wR3JJqKLxkFzuFOch76cVx8xe+Xn8t 3sExovOYe6EOqWprAW/wJr17LMR+p7isqEdHawfGwioh+aeYeTMeP9T7fOiDcg005 5pewlw2dUvZloaMw8YGqgVRPA+jfhNzK7wRh6Em9eg6v7TPZxnM8qU2THoSKASo70 YOf5vB8HCo+/sEXvBfdAOApuaUJFxLCaHj271d1dpVV8ahs5XQKRec3SluA1a3nnu PLwE8xKdhe5xfqX9f9tGJRCfQyPEa6HR2iNzlf9YOKM77qcZXmu6frcKSu5OmxraX /BHAivm1FVI3V16Hug== X-UI-Sender-Class: 724b4f7f-cbec-4199-ad4e-598c01a50d3a Received: from smtpclient.apple ([95.112.41.68]) by mail.gmx.net (mrgmx004 [212.227.17.190]) with ESMTPSA (Nemesis) id 1MfYLa-1syeaM2zZw-00pRlN; Sat, 01 Feb 2025 19:05:10 +0100 Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3776.700.51.11.1\)) From: Sebastian Moeller In-Reply-To: <4B1379B8-7EF6-4D34-8091-451A48585811@gmail.com> Date: Sat, 1 Feb 2025 19:05:00 +0100 Cc: =?utf-8?Q?Dave_T=C3=A4ht?= , David Collier-Brown , Rich Brown via Bloat Content-Transfer-Encoding: quoted-printable Message-Id: References: <48F77C27-0E57-4F96-9BD8-238CC93342F8@gmail.com> <9A110AF4-E976-4228-9FA6-92C5C99F611A@gmx.de> <48FB68A5-8320-4B46-97E1-4C67BB7B7B1B@gmx.de> <4B1379B8-7EF6-4D34-8091-451A48585811@gmail.com> To: Jonathan Morton X-Mailer: Apple Mail (2.3776.700.51.11.1) X-Provags-ID: V03:K1:LsKkOTBob4vjULUAogDLXYQcBww+0NiD4nrqCRQMmomYVDG5f15 ztJcUjTjUf+MGeIn6lTb4+rBBSrfvWYS91Gb4mF+MZOjLe2Yx5h+b+O2ZFJAz+8ljZXSaDr 3Ejhg0k2chSOrr3UxZwkQCgBkn46mmiYAJ0RRPpOrb+m9Ch5FBopnphMVeUOmuPYEOAuinr NC5vhhL/PyQJJYCpL/QxQ== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:9ShxlM1fuZo=;yNnizQvggB5VVtomZ0k+1AMz03Q DTwhND/Md9usZ5SyKU2d3XX4zU/xxZICO0TWQzcRRM5y840PEucU8NzQ8hZC2lg25bj5yrX1X CxMSU67hgmdp3S3Jx5TIEBRjd0RKirOxYa8xuACUc+a+VhaIP2wF1ADZbRclWZ2BO0EyGWnPO OEbIhPtL/N7o2xHDZLqARQcj3dpDq8oEP99b4EKsOTne4UhMf7X0Wr75TPv64Y6ZSDRjQr+vZ CrMSfDVt5bxocAwFvridmTh8cLAyKwFpX3aXqiPEOIxjrtOxiiPqZ7MS0CfjSdxdooFgUAZ0V lDZ8lAr3BGRDlJ0corKrstGBqHreL86pJGn1K5V8WtdMIySU5cVP2fx02ENOaGcKfwDai1+cr 5XSpA20ppIBcmQ8ep6DWcR7FKkqNgHtirXCQx+E9jB7oVYqAcQ9xSSNwju29j23b7ja2ToPMH C1zuTTV1JrL31A4zCovwMbzidoxi/6qffJuF3uSog9igSinW4430n5RTGvuzdxD33BNFmqsux UzoP84JNNfNqM+wO9lvSVT3YxxNdAWcYHei5HzoGBhejlntNXJxeytKTK3mrBbjMFno+rOUe4 b3g8vx5VcfUFeWmD8Y+9G9uVFUQ3bRX9wDJJqW16Jm+IJ+G30+9vOVHwtpcBp1BR2qsaT2B9M PrN2zSjwYV91602MRx74shpAZoZJT671GEw8PmruanQTxGJ7qzTTIxKpJT74Y5dHArb/nAKL/ a/cEwOskEaTdvGACO28TzE+99Oqw84zqIeuL382Qnhc0l4rf/lURurGJKEPCytxxYTvGTn8ar 3es4yv5m/74H1EhvcGgUlYm++zV13c9Rj5JBjB+pqxf4vTcJnfYqWeB/nNdITMULB6rCyBi3k JwMBeF58mcduWyI9+C+CMU1fs0NJKfngw1MS05olvX8crHMb74BhXsRsfmn/rfviG7WiATwXC JZbw1alco8UA8M/rrObxyRLfIOPU8JYEQKxruN8JU9m4fvXNX1rIzZ7ksK8FZdDjQARtMmdCH 4e9q7brdPdSwGbvLOyKDp2K2LSGmoK4EUOiUq1cIt3KxKCbRUxo6+yaiLzNJj6CCaSk+arwnC jVmgsIWWqAezHipruKPAOmte6BPpXxFnOS3oi+4SR2mO4VO29LI2Du3rLw10bPAa3msbbioUG x5bCxAbIUBpTKEuhvRg/t5V0ToEDVJ5WxuPn4EozMgSVXhuXCr9fGRUpxkiAHckaBwXcBXUBm jgnbNcGRaJCH2iG0ljItB2HK4hxv0vsM2/tdyJVSdj6SIIO4Rl6liLFljGbL1kEkvBcqPsVr8 8O2K9RNk7yzpXBQRqEgY7kKYdg6M8gXGdys7Dryt6JXX0s= 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 18:05:12 -0000 Hi Jonathan... > On 1. Feb 2025, at 18:26, Jonathan Morton = wrote: >=20 >> 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? >=20 > Codel's default 5ms target is already pretty tight, I am more concerned about the 100ms interval (target is linked to that), = waiting 100ms before engaging is not great if the true RTT is in the low = single digits... > about as tight as you can reasonably make it while still accommodating = typical levels of link-level jitter. =20 Not sure, in a LAN with proper back pressure I would guess lower than = 5ms to be achievable. This does not need to go crazy low, so 1 ms would = likely do well, with an interval of 10ms... or if 5 ms is truly a sweet = spot, maybe decouple interval and target so these can be configured = independently (in spite of the theory that recommends target to be 5-10% = of interval). > 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. Fair, and I am not after DCTCP style here (L4S would be) but simply = allowing a parallel codel for a tighter target. > 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. Great! May I propose something for you to ponder, assuming DelTic will = also include a traffic shaper?=20 One thing great with cake is the built-in traffic shaper, making setting = it up a breeze. However that shaper tends to be relatively CPU-hungry = (as shapers tend to be) and at the same time once it runs itself out of = CPU cycles tends to not honor its latency target as well HTB+fq_codel = tend to do. IIRC with HTB+fq_codel if you are CPI limited latency stays = low, throughput takes a hit, with cake it is more that latency increases = (not atrociously, even in that mode having cake is IMHO better than no = cake) while thropughput takes a smaller hit. Not sure that this is = something that can be easily addressed, but IMHO I prefer HTB+fq_codels = behaviour in that regards. >=20 > - Jonathan Morton