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 8C9CF3B2A4 for ; Thu, 1 Sep 2022 03:58:27 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1662019098; bh=cMTd2cx/u2AKpg+Oaiy8bo/SDlciaaM/nrPQvDYolrM=; h=X-UI-Sender-Class:Subject:From:In-Reply-To:Date:Cc:References:To; b=G4RyXY6DsjhlNSQwu8Q8fZRja2M8wUskUhy/EeixOgRN0foVYGmtLy47P0hM8uGPI SlcTjnPDjagNDdJTQnPUnOgLKZqlIFhUR4wF3TFHzlMBHM5MH3N/dxtaN49K3n+73L Ct5Ekae15KLHqN1C3ju8BcQxyYyXBwK6lwSfdXFM= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from smtpclient.apple ([134.76.241.253]) by mail.gmx.net (mrgmx105 [212.227.17.168]) with ESMTPSA (Nemesis) id 1M1ps8-1oVs0o1ONU-002E3A; Thu, 01 Sep 2022 09:58:18 +0200 Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3696.120.41.1.1\)) From: Sebastian Moeller In-Reply-To: <56e56b0f-07bd-fe0c-9434-2663ae9d4404@auckland.ac.nz> Date: Thu, 1 Sep 2022 09:58:16 +0200 Cc: David Lang , Ulrich Speidel via Starlink Content-Transfer-Encoding: quoted-printable Message-Id: <63B8B233-DF84-4D60-884F-8A83B3ED7607@gmx.de> References: <1661878433.14064713@apps.rackspace.com> <6p5n9262-3745-pq31-5636-1rnon987o255@ynat.uz> <20220830220710.GA2653@sunf10.rd.bbc.co.uk> <15982a40-2b34-7ed1-bfa3-bced03fc3839@auckland.ac.nz> <9CE05D69-FC37-4C97-9D8D-D46B2DF6DE16@gmx.de> <2321be3b-957f-2d1f-c335-119c8e76efe5@auckland.ac.nz> <8978587-42op-q175-2o41-qq9p4491459s@ynat.uz> <56e56b0f-07bd-fe0c-9434-2663ae9d4404@auckland.ac.nz> To: Ulrich Speidel X-Mailer: Apple Mail (2.3696.120.41.1.1) X-Provags-ID: V03:K1:zyx2eEzkw9oNrcpaMY0HJUhQb+iM4oOnqOI+ieQSjixOv8wVWi0 7SNWhGFJHmXBkJ/okM9y5WuC1f9MfErC9gnkWPgGKRDA1q2pyfNCv0qso4pDfsEKpjQ/xEN fXRBLLh3ILmv9r3MVCNlXe57T8sRYGtxHHfqq8/JlvXQfmFENWZtWH1X32a+lQBW9PURm9h 3lRVszoklembHtVuyVnog== X-Spam-Flag: NO X-UI-Out-Filterresults: notjunk:1;V03:K0:mM47U1a1zSM=:PBcA7W+R8e4NAlu0LUHl4w 3fsDk9s7lDMXkYWLdnFpqKg5r5XX+HMD1zy3/a1OvmYXwt2dJ4y8SSYuQS7+0Rt+0mcaNLsls /7uBn60XbcbIJ3DlBWWMhe3Tdvi8HNrUX3pkWakty3U9lpVN2OuZRWqtLT+qaH5ewdcLEy3ML LGMbQ0s15FinUXT8tIaocZcNZbcUiVcDUcO3OmJi/KlG8gCjWPUWZr3REH0oy+/YfsIMg5toA FHi57RlfdLEiMZ/VJ6wH9RimSO506dipcvySUFPjRLBYFTgJb69kKzTzKyDxivmSYTXTniuPn Qk5FN42rKKbDriF6veu3hH2cUN63ScD08igyHePAp6RaFWKIjrc3kijXxXkKw48UQtfCaVPPd ZAixCLZHvlr8no/Cck22dAYBEJXHBCHeoefa82s622r5Htyz9mifYgc1RjtCDk0swKMXeYYpZ aOFNkwGt/GaWt5GqcZqZ18pMLIZ+GnajFhdlVVcwvMmuj/0z/aZSktLrwIfWLVC+x4Pi5RnKH 29G2hLxKNfA7xchXuT+/76KT2TWA4tMHYPyRSBaNoirNim4dIRKULzT91Uf7Orv/+kRXiACgu 0PnGVDPfW7DG03R8AdVsgxpuX7emZ+4wTTnMaulcRSKXp+R1+E2suj1FpD5OO/Ym917a3IvkT cXuW0nUiWtRgjmPtLmhm2L44xDYlVIse/4e2vxp89NWvx28WXxgZM0HM/Nx82kZ2CUyLZcGSX c3ZA4JKjSOy68Jgiz9tLbKGDLoWTzuiKoUCrDfxY1j6edlx1+Nhkg8luwucwCAZ7vmqAj+RF0 fNSf7jUhKbPTMfyeYQ2+V4yqbPzYdmoYZzuQJjULOV40FgIhhedMbPTCuX1zXfjEbvMFCVSCP deQs0ctHUVwDfrWfP9MNGb6ZoM7jPG/nd02EcRFpEVY51/NNV8LWf/Qkf/ge3s1iJSGZveoUu E2bLMf9fH2+t9E2wKZ7AdIi4GCNJtaXmG73nroaEYaW907Wr2a8Pu18KTRz6LhY03MKnXVmlx E2W9tT5e0xE4P6xzVY5w+BJ7MXsnH9ezVUQAe8HOjatCDLCyf0+HVE6ACEKhRHl8wbSDG1Rn3 374rUDTxf0R9ZGo0mN6DNlAVV+68ye1mpWQYmWAAqLsg/6xijYUQwohwQ== Subject: Re: [Starlink] Starlink "beam spread" 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: Thu, 01 Sep 2022 07:58:27 -0000 Hi Ulrich, focussing on the CDN part > On Aug 31, 2022, at 15:41, Ulrich Speidel = wrote: > [...] > CDNs & Co - are NOT just dumb economic optimisations to lower bit = miles. They actually improve performance, and significantly so. A lower = RTT between you and a server that you grab data from via TCP allows a = much faster opening of the congestion window. With initial TCP cwnd's = being typically 10 packets or around 15 kB of data, having a server = within 10 ms of your client means that you've transferred 15 kB after 5 = ms, 45 kB after 10 ms, 105 kB after 15 ms, 225 kB after 20 ms, and 465 = kB after 25 ms. Make your RTT 100 ms, and it takes half a second to get = to your 465 kB. Having a CDN server in close topological proximity also = generally reduces the number of queues between you and the server at = which packets can die an untimely early death, and generally, by taking = load off such links, reduces the probability of this happening at a lot = of queues. Bottom line: Having a CDN keeps your users happier. Also, = live streaming and video conferencing aside, most video is not multicast = or broadcast, but unicast. > [...] Sure, that is a consequence of slow start*, but I argue that having 2ms = or 20ms is not going to result in too noticeable a slow down, and bulk = transfers like movies really do not care since DASH in all likelihood = leaves slow-start for good after the initial ramp-up. Yes, 1ms versus = 100ms makes a difference for interactive uses, but putting the CDN in = space versus at the base station IMHO is a less clear improvement. Add = to this that caches partly work by exploiting "locality", so e.g. for = video streaming platforms I expect different countries to have different = viewing profiles and hence different content needs to be cached, but = satellites cover large "rings" around the world; meaning either you = cache everything (or at least the content for your primary market) in = space multiple times over so that your main service area is covered at = all times or... I am prepared to eat crow on this in the future, but I am highly = skeptical about CDNs in space (in spite of it being a cool project from = the technological side). *) As it looks slow start is getting a bad rep from multiple sides, but = I see not better alternative out there that solves the challenge = slow-start tackles in a better way. Namely gradual ramping and probing = of sending rates/congestion windows to avoid collapse, this in turn = means that short flows will never reach capacity, the solution to which = might well be, use longer flows then...=