From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.gmx.net (mout.gmx.net [212.227.17.21]) (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 982083B2A4 for ; Mon, 14 Feb 2022 12:15:58 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1644858956; bh=7SWc0Jgnu8wd+Giy7HhJ6UiXmlqSyQfjUFUwrtBUB30=; h=X-UI-Sender-Class:Subject:From:In-Reply-To:Date:Cc:References:To; b=BHoHlp3EXjqIsZigiSTb/+MYmk1zuFMr/y0uyeNMLW4PQJf+0O8BVFHvsecr1Uvtj FwIDV3yX3u2HLD1xG2ASyJrWt2+dKqklk/Ln8erHeLrCud2fdM6rHHcE1eCIpz9Duy YagSHBNFhbPMbsTZNVGStKPwjLTITVjhCgX6/qLc= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from smtpclient.apple ([134.76.241.253]) by mail.gmx.net (mrgmx104 [212.227.17.168]) with ESMTPSA (Nemesis) id 1MgNh1-1nvkSh2LxH-00hxyA; Mon, 14 Feb 2022 18:15:56 +0100 Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.120.0.1.13\)) From: Sebastian Moeller In-Reply-To: Date: Mon, 14 Feb 2022 18:15:55 +0100 Cc: =?utf-8?Q?Dave_T=C3=A4ht?= , starlink@lists.bufferbloat.net Content-Transfer-Encoding: quoted-printable Message-Id: <3157ED41-1438-4519-9E84-847404BE229D@gmx.de> References: <4AFF4380-4AA5-47C5-8BF0-440101A3D788@gmx.de> To: =?utf-8?Q?Bj=C3=B8rn_Ivar_Teigen?= X-Mailer: Apple Mail (2.3654.120.0.1.13) X-Provags-ID: V03:K1:PZsaYIPsxJH5LXLFoji2xWsQMkFm6v4dfIXnUBpqUENT+KfH4E6 4A9Hzj5LFSN2h4XPlZGla14kiuuM8xDrSGQuJfMXd64rnbUhszAvfYZbexTbV9bk5nMCtUg 4/P7GOPx2BKj0ZIbBMU8X+dhXbxZIq2LMetPG1ReZIWXt09iqUvNO0mfFzzAaetJ2/B8069 O6lYqGUi98umQr17EO9wQ== X-Spam-Flag: NO X-UI-Out-Filterresults: notjunk:1;V03:K0:i79qtyfH2xc=:7Bp9VVfplRf3ZyTZnPuhLg PnsY1OiTm0Pv3RhQoW7c061dbOBsA+HnOWwlRigmvrtxEAJduYynvQD78oHY2E53+Kz+FS+AV DMs7oQyX3Y73QCsFIomsnNOF1wmx9ckIISNsxmZkU7+XRSx2QIErv30yQaATUwypKWMHo1GV7 5NpF2P4kQIGUxE/RTpBeUkDz+qTZZpOpJ6R1cH4h0o9Y0j9YhoLSumrmVAgaYCbI4ObAOgKMb KsS0QQMJNBSdnJiVEvusVxDnr0bzLf/H1b7oWo5jCZC8bMtgzVf9258XO8U5amg1CIp9Q1aWs y+Hst0JZQZyr2+e0abFDrgrf5OMH2CuorbYKt9NaOe3+RB/6j/V7UrC1xN2OsX8APL6RY511b MrPh3JbIGP/cK4CbYgHPbW04qxhiAQ3gmv/rEbeXR+cUoVqe/tGnvKKzzze7qdthwZeIbTh4x YMZrd+jjP+wYdWGhwPOug7JQhWtU3n/UQISv70YuMbj2/wVaTcS4YpE4Bj6GwTFtcIZz2z9mB KXf0iYODQO+/q/kBpFVzPnTJCUcNUc96yLEdnNyoWSY7QJrgz3nNCptTMelKxxI8Z6zszXwMH qKFgrlnBnlph7nM9HyVU4/+imKEZmpxcyI+78nCwkWjMeg2sCmauFDmTBykE7xFd6+7IB8Stv BXg6c8d3+vbNRCH4DKEahccsY8qfsIq1hswmTrL3tsP1q4VpTwp+0c1zM2X0TeM6si7iQvKGX Wm7s4E7683fA5WuhdI90dD+WW0cGiLeGkHxWfD928FeAo12f6xM5J9hhQvf5HoVdVW4gWh2AQ C6bvtXiUFU3+APPERUYdzmmbupk2ooH2m6faTsZzT1bpt8Sv+Qyr//nrbWv8ny94tUIQ1yjeR Y4Bnyu2wfCytlSuotEYnN/lw8yLRpZnQ+i/tfdeUGmQEWa3Q/lyw/QB6PQf/2pYmDrxxk16/4 XhAE7KYHicib6FKoWNX9SEZdEjydquuNpioJydzEzVufYFURbdzUotXvUdPpAvwj7PJKc0tfR OeHYQV3PdCIYG51JCmFgRiFEt8zAduNJtwT6OnyOL+T4t8p38rGv90GSEyQY6zMCqLVCZiW1/ BGM23/BCjxGzbE= Subject: Re: [Starlink] Network quality for rocket scientists X-BeenThere: starlink@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: "Starlink has bufferbloat. Bad." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 14 Feb 2022 17:15:59 -0000 Hi Bj=C3=B8rn, I guess I should have started with the obvious. Nice short article! > On Feb 14, 2022, at 17:32, Bj=C3=B8rn Ivar Teigen = wrote: >=20 > Hi Sebastian, thank you for the feedback. >=20 > "See the problem? Buffers produce jitter!" >=20 >=20 > I would rephrase that as "over-sized and under-managed" buffers = increase jitter unduly. Interestingly, bound jitter can be converted = into static latency by using, wait for it, (delay) buffers and a = scheduler. >=20 > You are absolutely right. I was hoping someone would spot that! There = is one problem with that approach though. To actually remove the jitter = the scheduler can no longer be work-conserving (needs delay as you also = point out), and that increases TCP ramp-up times (among other things). = Can be a hard sell. I think the benefits outweigh the costs though, so I = would do it your way. But that is what end-points already do, on-line games do this to = equalize internet access quality between players (allowing them to make = matches over larger populations), as do DASH type video streaming = applications, where the isochronous play-out takes the role of the = scheduler and the race-to-fill-the-play-out-buffers serves to keep the = buffers filled so the scheduler never runs "dry". >=20 > >=20 > > Only nit is at the conclusion... the benefits of applying fair = queuing > > to level out apparent jitter is well demonstrated at this point, for > > most kinds of traffic. Wish you'd mentioned it. >=20 > I rather wish low latency DOCSIS (LLD) aka L4S's primary = driver/use-case would not have been mentioned before it has been = properly tested and confirmed delivering on its promises. Because most = of what L4S offers/mandates for jitter reduction is "hopes and prayers", = aka end-points are supposed to behave well... in fairness LLD at least = has a poor man's FQ on board in the guise of "queue protection" (with by = default like 32 "buckets")... some of the cost of FQ with only few of = its benefits... > Fair enough, time will show!=20 Given Pete's data at https://github.com/heistp/l4s-tests I am = cautious to hold my breath... or to put it differently, I am certain = they will not deliver on their promises, the bigger question is whether = the incremental improvement they offer (over the default FIFO) is decent = enough to retroactively justify the disruption they will have caused... Regards Sebastian > =20 > Regards > Sebastian >=20 >=20 >=20 > >=20 > >=20 > > On Mon, Feb 14, 2022 at 7:07 AM Bj=C3=B8rn Ivar Teigen = wrote: > >>=20 > >> Hi everyone, > >>=20 > >> I was inspired by the latest Starship presentation to write a piece = on network quality in the language of rocket science. The blog can be = found here: = https://www.domos.no/news-updates/network-quality-for-rocket-scientists > >>=20 > >> Cheers, > >> Bj=C3=B8rn Ivar Teigen > >>=20 > >> -- > >> Bj=C3=B8rn Ivar Teigen > >> Head of Research > >> +47 47335952 | bjorn@domos.no | www.domos.no > >> WiFi Slicing by Domos > >> _______________________________________________ > >> Starlink mailing list > >> Starlink@lists.bufferbloat.net > >> https://lists.bufferbloat.net/listinfo/starlink > >=20 > >=20 > >=20 > > --=20 > > I tried to build a better future, a few times: > > https://wayforward.archive.org/?site=3Dhttps%3A%2F%2Fwww.icei.org > >=20 > > Dave T=C3=A4ht CEO, TekLibre, LLC > > _______________________________________________ > > Starlink mailing list > > Starlink@lists.bufferbloat.net > > https://lists.bufferbloat.net/listinfo/starlink >=20 >=20 >=20 > --=20 > Bj=C3=B8rn Ivar Teigen > Head of Research > +47 47335952 | bjorn@domos.no | www.domos.no > WiFi Slicing by Domos