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Fri, 13 Aug 2021 01:55:59 +0000 From: Ulrich Speidel To: starlink@lists.bufferbloat.net References: <7AB190E6-A974-42A4-982F-5071CA45F31E@onholyground.com> <786faf6a-988d-ff29-42a6-44b508bf6625@cs.auckland.ac.nz> Message-ID: Date: Fri, 13 Aug 2021 13:55:56 +1200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 In-Reply-To: X-ClientProxiedBy: SYYP282CA0006.AUSP282.PROD.OUTLOOK.COM (2603:10c6:10:b4::16) To SY4PR01MB6979.ausprd01.prod.outlook.com (2603:10c6:10:142::13) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [IPv6:2001:df0:0:2006:d451:d1b1:f7b6:a330] (2001:df0:0:2006:d451:d1b1:f7b6:a330) by SYYP282CA0006.AUSP282.PROD.OUTLOOK.COM (2603:10c6:10:b4::16) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4415.14 via Frontend Transport; Fri, 13 Aug 2021 01:55:58 +0000 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: d1098c38-f723-4057-b7a6-08d95dfd7edd X-MS-TrafficTypeDiagnostic: SY4PR01MB6491: X-MS-Exchange-Transport-Forked: True X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:9508 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0 X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable Content-Language: en-US Subject: Re: [Starlink] speedtest.net takes a look at sat internet around the globe 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: Fri, 13 Aug 2021 01:56:05 -0000 On 13/08/2021 11:24 am, Ricky Mok wrote: > > I think the blog used the data they collected from speedtest.net. I=20 > conducted research on that topic. Ookla's speedtest is TCP based=20 > (usually 4-6 concurrent TCP flows to a test server). Ookla deployed=20 > over 12k test servers (many ISPs contributed to it). The test used IP=20 > geolocation to pick a set of ten nearest servers geographically and=20 > establish WebSocket to send "ping"s to test the network latency. The=20 > test then chooses the server with the lowest latency and send 10 more=20 > probes to test the RTTs. The "latency" they referred should be the=20 > extract from the RTT tests. > That's lumping in a lot of other factors here that have little to do=20 with the technology: Even if you do TCP-based tests, it's a matter of=20 how long you allow these to ramp up for (cwnd opening speed depends=20 crucially on RTT between endpoints). How much congestion exists on the=20 path between server and last mile - pings don't necessarily tell you=20 that. It's also relying on the topological accuracy of geolocation.=20 Geographical proximity !=3D topological proximity in the age of BGP and=20 tiered ISPs (we've seen a great deal of traffic between NZ and Asia go=20 via the mainland US - and this went on for years!). But most=20 importantly, you're comparing mature networks with decades of=20 underinvestment and a heavy user load against a new network with light=20 beta user load. > > I think it is a norm to have shared last mile and advertise the "max"=20 > capacity, just like what cable providers did. > In the case of Starlink, that last mile is awfully long, though... > > I remembered when they start launching the beta test. Only that=20 > latitude range had continuous satellite coverage. I assume the service=20 > outside that range would be unstable. But they have ground station=20 > built out of that range already. So, they just need to launch more=20 > SpaceX rockets... > Indeed. But there is more to this than that. Basically, each satellite=20 in an inclined orbit crosses each parallel (latitude) up to its=20 inclination twice per orbit. Since there is a lot less length of=20 parallel at higher-numbered latitudes, parallels with latitudes close=20 the the inclination get more satellite crossings per mile of parallel=20 per hour. So more rockets isn't going to change the density disparity=20 unless their satellites will go into orbits with vastly different=20 inclinations (which I hope they will). > > For CDN, they signed agreements with Google (and Azure?) I expect=20 > ground stations have direct interconnection with the cloud providers=20 > for content. They can also have caches installed in the ground station=20 > (e.g., netflix, youtube), similar to some ordinary ISPs installed=20 > in-network caches in Central Offices. However, i agree that they=20 > cannot do caching on the satellites, particularly we have HTTPS :) > That still puts them on the wrong side of the link ;-) Honestly, I can understand Americans' and Canadian frustrations with=20 their ISPs in rural areas, but compared to people who simply cannot get=20 Internet from any other source than satellite for reasons of remoteness,=20 depth of ocean or impenetrability of jungle or mountains, that=20 regulatory problem is very much a first world one ;-) --=20 **************************************************************** Dr. Ulrich Speidel School of Computer Science Room 303S.594 (City Campus) Ph: (+64-9)-373-7599 ext. 85282 The University of Auckland ulrich@cs.auckland.ac.nz =20 http://www.cs.auckland.ac.nz/~ulrich/ ****************************************************************