From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from vsmx002.dclux.xion.oxcs.net (vsmx002.dclux.xion.oxcs.net [185.74.65.108]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 5F80A3B29E for ; Fri, 16 Jul 2021 17:40:28 -0400 (EDT) Received: from proxy-2.proxy.oxio.ns.xion.oxcs.net (proxy-2.proxy.oxio.ns.xion.oxcs.net [83.61.18.4]) by mx-out.dclux.xion.oxcs.net (Postfix) with SMTP id A40538C0849; Fri, 16 Jul 2021 21:40:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=dclux.xion.oxcs.net; s=mail1; t=1626471627; bh=1CzdI0aTB9cDA6+Svygycun4W4u1SC0loh0lY65wl/M=; h=Date:From:To:Cc:In-Reply-To:References:Subject:From; b=vMA/n5GbXE82CtHB/Zv5FZ/dOiZ7MkfrHUBGrouX8ZidvV6tiv20oSq5uG4H9gJVp NpIfEJ5J5EsyXSDAkXt0OilhNBeyWEtDTMew5dvUuGjJ5eaY1hT5GOJNmX8/vs7j2s 83lCrqmFRkI0c+eLUZXcxQHprrRCpTeFybg/6nzXSs+VCu7uwJmJ5llClri4T1GiTD 52Ky9T/Jte0TDlHfVu3BNIeTv3JR/Japfgs/WOSqXPal1QYlqAS0MqL8tdIpsM/ZFZ 7DZWg7MeeGjMhegLRjGdBxkI3MLLVPLat/PXTBI+kgJnQ+ZXSm644D/FALqHWtzStU /O3MRLLWv1pvw== Date: Fri, 16 Jul 2021 23:40:15 +0200 From: Mike Puchol To: David Lang Cc: Nathan Owens , "=?utf-8?Q?starlink=40lists.bufferbloat.net?=" , "David P. Reed" Message-ID: In-Reply-To: References: <1625856001.74681750@apps.rackspace.com> <33ae5470-a05a-484e-adc6-4baca6ede9ad@Spark> X-Readdle-Message-ID: c4258bcd-b193-4015-9d69-4cf3b8ea817a@Spark MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="60f1fcc4_1ba026fa_bde9" X-VadeSecure-Status: LEGIT X-VADE-STATUS: LEGIT Subject: Re: [Starlink] Starlink and bufferbloat status? 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, 16 Jul 2021 21:40:28 -0000 --60f1fcc4_1ba026fa_bde9 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline If we understand shell as =E2=80=9Cgroup of satellites at a certain altit= ude range=E2=80=9D, there is not much point in linking between shells if = you can link within one shell and orbital plane, and that plane has at le= ast one satellite within range of a gateway. I could be proven wrong, but= IMHO the first generation of links are meant of intra-plane, and maybe a= t a stretch cross-plane to the next plane East or West. The only way to eventually go is optical links to the ground too, as R=46= will only get you so far. At that stage, every shell will have its own o= ptical links to the ground, with gateways placed in areas with little ave= rage cloud cover. Best, Mike On Jul 16, 2021, 23:30 +0200, David Lang , wrote: > at satellite distances, you need to adjust your vertical direction depe= nding on > how far away the satellite you are talking to is, even if it's at the s= ame > altitude > > the difference between shells that are only a few KM apart is less than= the > angles that you could need to satellites in the same shell further away= . > > David Lang > > On =46ri, 16 Jul 2021, Mike Puchol wrote: > > > Date: =46ri, 16 Jul 2021 22:57:14 +0200 > > =46rom: Mike Puchol > > To: David Lang > > Cc: Nathan Owens , > > =22starlink=40lists.bufferbloat.net=22 , > > David P. Reed > > Subject: Re: =5BStarlink=5D Starlink and bufferbloat status=3F > > > > Correct. A mirror tracking head that turns around the perpendicular t= o the satellite path allows you to track satellites in the same plane, in= front or behind, when they change altitude by a few kilometers as part o= f orbital adjustments or collision avoidance. To have a fully gimbaled he= ad that can track any satellite in any direction (and at any relative vel= ocity=21) is a totally different problem. I could see satellites linked t= o the next longitudinal plane apart from those on the same plane, but cro= ss-plane when one is ascending and the other descending is way harder. Th= e next shells will be at lower altitudes, around 300-350km, and they have= also stated they want to go for higher shells at 1000+ km. > > > > Best, > > > > Mike > > On Jul 16, 2021, 20:48 +0200, David Lang , wrote: > > > I expect the lasers to have 2d gimbles, which lets them track most = things in > > > their field of view. Remember that Starlink has compressed their or= bital planes, > > > they are going to be running almost everything in the 550km range (= 500-600km > > > IIRC) and have almost entirely eliminated the =7E1000km planes > > > > > > David Lang > > > > > > On =46ri, 16 Jul 2021, > > > Mike Puchol wrote: > > > > > > > Date: =46ri, 16 Jul 2021 19:42:55 +0200 > > > > =46rom: Mike Puchol > > > > To: David Lang > > > > Cc: Nathan Owens , > > > > =22starlink=40lists.bufferbloat.net=22 , > > > > David P. Reed > > > > Subject: Re: =5BStarlink=5D Starlink and bufferbloat status=3F > > > > > > > > True, but we are then assuming that the optical links are a mesh = between satellites in the same plane, plus between planes. =46rom an engi= neering problem point of view, keeping optical links in-plane only makes = the system extremely simpler (no full =46OV gimbals with the optical trai= n in them, for example), and it solves the issue, as it is highly likely = that at least one satellite in any given plane will be within reach of a = gateway. > > > > > > > > Routing to an arbitrary gateway may involve passing via intermedi= ate gateways, ground segments, and even using terminals as a hopping poin= t. > > > > > > > > Best, > > > > > > > > Mike > > > > On Jul 16, 2021, 19:38 +0200, David Lang , wrote= : > > > > > the speed of light in a vaccum is significantly better than the= speed of light > > > > > in fiber, so if you are doing a cross country hop, terminal -> = sat -> sat -> sat > > > > > -> ground station (especially if the ground station is in the t= arget datacenter) > > > > > can be faster than terminal -> sat -> ground station -> cross-c= ountry fiber, > > > > > even accounting for the longer distance at 550km altitude than = at ground level. > > > > > > > > > > This has interesting implications for supplementing/replacing u= ndersea cables as > > > > > the sats over the ocean are not going to be heavily used, dedic= ated ground > > > > > stations could be setup that use sats further offshore than nor= mal (and are > > > > > shielded from sats over land) to leverage the system without in= terfering > > > > > significantly with more 'traditional' uses > > > > > > > > > > David Lang > > > > > > > > > > On =46ri, 16 Jul 2021, Mike Puchol wrote: > > > > > > > > > > > Date: =46ri, 16 Jul 2021 19:31:37 +0200 > > > > > > =46rom: Mike Puchol > > > > > > To: David Lang , Nathan Owens > > > > > > Cc: =22starlink=40lists.bufferbloat.net=22 , > > > > > > David P. Reed > > > > > > Subject: Re: =5BStarlink=5D Starlink and bufferbloat status=3F= > > > > > > > > > > > > Satellite optical links are useful to extend coverage to area= s where you don=E2=80=99t have gateways - thus, they will introduce addit= ional latency compared to two space segment hops (terminal to satellite -= > satellite to gateway). If you have terminal to satellite, two optical h= ops, then final satellite to gateway, you will have more latency, not les= s. > > > > > > > > > > > > We are being =E2=80=9Csold=E2=80=9D optical links for what th= ey are not IMHO. > > > > > > > > > > > > Best, > > > > > > > > > > > > Mike > > > > > > On Jul 16, 2021, 19:29 +0200, Nathan Owens , wrote: > > > > > > > > As there are more satellites, the up down time will get c= loser to 4-5ms rather then the =7E7ms you list > > > > > > > > > > > > > > Possibly, if you do steering to always jump to the lowest l= atency satellite. > > > > > > > > > > > > > > > with laser relays in orbit, and terminal to terminal rout= ing in orbit, there is the potential for the theoretical minimum to tend = lower > > > > > > > Maybe for certain users really in the middle of nowhere, bu= t I did the best-case math for =22bent pipe=22 in Seattle area, which is = as good as it gets. > > > > > > > > > > > > > > > On =46ri, Jul 16, 2021 at 10:24 AM David Lang wrote: > > > > > > > > > hey, it's a good attitude to have :-) > > > > > > > > > > > > > > > > > > Elon tends to set 'impossible' goals, miss the timeline= a bit, and come very > > > > > > > > > close to the goal, if not exceed it. > > > > > > > > > > > > > > > > > > As there are more staellites, the up down time will get= closer to 4-5ms rather > > > > > > > > > then the =7E7ms you list, and with laser relays in orbi= t, and terminal to terminal > > > > > > > > > routing in orbit, there is the potential for the theore= tical minimum to tend > > > > > > > > > lower, giving some headroom for other overhead but stil= l being in the 20ms > > > > > > > > > range. > > > > > > > > > > > > > > > > > > David Lang > > > > > > > > > > > > > > > > > > =C2=A0 On =46ri, 16 Jul 2021, Nathan Owens wrote: > > > > > > > > > > > > > > > > > > > Elon said =22foolish packet routing=22 for things ove= r 20ms=21 Which seems crazy > > > > > > > > > > if you do some basic math: > > > > > > > > > > > > > > > > > > > > =C2=A0 =C2=A0- Sat to User Terminal distance: 550-950= km air/vacuum: 1.9 - 3.3ms > > > > > > > > > > =C2=A0 =C2=A0- Sat to GW distance: 550-950km air/vacu= um: 1.9 - 3.3ms > > > > > > > > > > =C2=A0 =C2=A0- GW to PoP Distance: 50-800km fiber: 0.= 25 - 4ms > > > > > > > > > > =C2=A0 =C2=A0- PoP to Internet Distance: 50km fiber: = 0.25 - 0.5ms > > > > > > > > > > =C2=A0 =C2=A0- Total one-way delay: 4.3 - 11.1ms > > > > > > > > > > =C2=A0 =C2=A0- Theoretical minimum RTT: 8.6ms - 22.2m= s, call it 15.4ms > > > > > > > > > > > > > > > > > > > > This includes no transmission delay, queuing delay, > > > > > > > > > > processing/fragmentation/reassembly/etc, and no time-= division multiplexing. > > > > > > > > > > > > > > > > > > > > On =46ri, Jul 16, 2021 at 10:09 AM David Lang wrote: > > > > > > > > > > > > > > > > > > > > > I think it depends on if you are looking at datacen= ter-to-datacenter > > > > > > > > > > > latency of > > > > > > > > > > > home to remote datacenter latency :-) > > > > > > > > > > > > > > > > > > > > > > my rule of thumb for cross US ping time has been 80= -100ms latency (but > > > > > > > > > > > it's been > > > > > > > > > > > a few years since I tested it). > > > > > > > > > > > > > > > > > > > > > > I note that an article I saw today said that Elon i= s saying that latency > > > > > > > > > > > will > > > > > > > > > > > improve significantly in the near future, that up/d= own latency is =7E20ms > > > > > > > > > > > and the > > > > > > > > > > > additional delays pushing it to the 80ms range are = 'stupid packet routing' > > > > > > > > > > > problems that they are working on. > > > > > > > > > > > > > > > > > > > > > > If they are still in that level of optimization, it= doesn't surprise me > > > > > > > > > > > that > > > > > > > > > > > they haven't really focused on the bufferbloat issu= e, they have more > > > > > > > > > > > obvious > > > > > > > > > > > stuff to fix first. > > > > > > > > > > > > > > > > > > > > > > David Lang > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > =C2=A0 =C2=A0On =46ri, 16 Jul 2021, Wheelock, Ian w= rote: > > > > > > > > > > > > > > > > > > > > > > > Date: =46ri, 16 Jul 2021 10:21:52 +0000 > > > > > > > > > > > > =46rom: =22Wheelock, Ian=22 > > > > > > > > > > > > To: David Lang , David P. Reed <= dpreed=40deepplum.com> > > > > > > > > > > > > Cc: =22starlink=40lists.bufferbloat.net=22 > > > > > > > > > > > > Subject: Re: =5BStarlink=5D Starlink and bufferbl= oat status=3F > > > > > > > > > > > > > > > > > > > > > > > > Hi David > > > > > > > > > > > > In terms of the Latency that David (Reed) mention= ed for California to > > > > > > > > > > > Massachusetts of about 17ms over the public interne= t, it seems a bit faster > > > > > > > > > > > than what I would expect. My own traceroute via my = VDSL link shows 14ms > > > > > > > > > > > just to get out of the operator network. > > > > > > > > > > > > > > > > > > > > > > > > https://www.wondernetwork.com=C2=A0 is a handy to= ol for checking geographic > > > > > > > > > > > ping perf between cities, and it shows a min of abo= ut 66ms for pings > > > > > > > > > > > between Boston and San Diego > > > > > > > > > > > https://wondernetwork.com/pings/boston/San%20Diego = (so about 33ms for > > > > > > > > > > > 1-way transfer). > > > > > > > > > > > > > > > > > > > > > > > > Distance wise this is about 4,100 KM (2,500 M), a= nd =402/3 speed of light > > > > > > > > > > > (through a pure fibre link of that distance) the pr= opagation time is just > > > > > > > > > > > over 20ms. If the network equipment between the Bos= ton and San Diego is > > > > > > > > > > > factored in, with some buffering along the way, 33m= s does seem quite > > > > > > > > > > > reasonable over the 20ms for speed of light in fibr= e for that 1-way transfer > > > > > > > > > > > > > > > > > > > > > > > > -Ian Wheelock > > > > > > > > > > > > > > > > > > > > > > > > =46rom: Starlink on behalf of > > > > > > > > > > > David Lang > > > > > > > > > > > > Date: =46riday 9 July 2021 at 23:59 > > > > > > > > > > > > To: =22David P. Reed=22 > > > > > > > > > > > > Cc: =22starlink=40lists.bufferbloat.net=22 > > > > > > > > > > > > Subject: Re: =5BStarlink=5D Starlink and bufferbl= oat status=3F > > > > > > > > > > > > > > > > > > > > > > > > IIRC, the definition of 'low latency' for the =46= CC was something like > > > > > > > > > > > 100ms, and Musk was predicting <40ms. roughly compe= titive with landlines, > > > > > > > > > > > and worlds better than geostationary satellite (and= many > > > > > > > > > > > > External (mailto:david=40lang.hm) > > > > > > > > > > > > > > > > > > > > > > > https://shared.outlook.inky.com/report=3Fid=3DY29tb= XNjb3BlL2lhbi53aGVlbG9ja0Bjb21tc2NvcGUuY29tL2I1Mz=46jZDA4OTZmMWI0Yzc5Nzdi= OTIzNmY3MTAzM2MxLzE2MjU4NzE1NDkuNjU=3D=23key=3D19e8545676e28e577c813de83a= 4cf1dc > > > > > > > > > > > =C2=A0 https://www.inky.com/banner-faq/=C2=A0 https= ://www.inky.com > > > > > > > > > > > > > > > > > > > > > > > > IIRC, the definition of 'low latency' for the =46= CC was something like > > > > > > > > > > > 100ms, and > > > > > > > > > > > > Musk was predicting <40ms. > > > > > > > > > > > > > > > > > > > > > > > > roughly competitive with landlines, and worlds be= tter than geostationary > > > > > > > > > > > > satellite (and many wireless ISPs) > > > > > > > > > > > > > > > > > > > > > > > > but when doing any serious testing of latency, yo= u need to be wired to > > > > > > > > > > > the > > > > > > > > > > > > router, wifi introduces so much variability that = it swamps the signal. > > > > > > > > > > > > > > > > > > > > > > > > David Lang > > > > > > > > > > > > > > > > > > > > > > > > On =46ri, 9 Jul 2021, David P. Reed wrote: > > > > > > > > > > > > > > > > > > > > > > > > > Date: =46ri, 9 Jul 2021 14:40:01 -0400 (EDT) > > > > > > > > > > > > > =46rom: David P. Reed > > > > > > > > > > > > > To: starlink=40lists.bufferbloat.net > > > > > > > > > > > > > Subject: =5BStarlink=5D Starlink and bufferbloa= t status=3F > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Early measurements of performance of Starlink h= ave shown significant > > > > > > > > > > > bufferbloat, as Dave Taht has shown. > > > > > > > > > > > > > > > > > > > > > > > > > > But...=C2=A0 Starlink is a moving target. The b= ufferbloat isn't a hardware > > > > > > > > > > > issue, it should be completely manageable, starting= by simple firmware > > > > > > > > > > > changes inside the Starlink system itself. =46or ex= ample, implementing > > > > > > > > > > > fq=5Fcodel so that bottleneck links just drop packe= ts according to the Best > > > > > > > > > > > Practices R=46C, > > > > > > > > > > > > > > > > > > > > > > > > > > So I'm hoping this has improved since Dave's me= asurements. How much has > > > > > > > > > > > it improved=3F What's the current maximum packet la= tency under full > > > > > > > > > > > load,=C2=A0 Ive heard anecdotally that a friend of = a friend gets 84 msec. *ping > > > > > > > > > > > times under full load*, but he wasn't using flent o= r some other measurement > > > > > > > > > > > tool of good quality that gives a true number. > > > > > > > > > > > > > > > > > > > > > > > > > > 84 msec is not great - it's marginal for Zoom q= uality experience (you > > > > > > > > > > > want latencies significantly less than 100 msec. as= a rule of thumb for > > > > > > > > > > > teleconferencing quality). But it is better than Da= ve's measurements showed. > > > > > > > > > > > > > > > > > > > > > > > > > > Now Musk bragged that his network was =22low la= tency=22 unlike other high > > > > > > > > > > > speed services, which means low end-to-end latency.= =C2=A0 That got him > > > > > > > > > > > permission from the =46CC to operate Starlink at al= l. His number was, I > > > > > > > > > > > think, < 5 msec. 84 is a lot more than 5. (I didn't= believe 5, because he > > > > > > > > > > > probably meant just the time from the ground statio= n to the terminal > > > > > > > > > > > through the satellite. But I regularly get 17 msec.= between California and > > > > > > > > > > > Massachusetts over the public Internet) > > > > > > > > > > > > > > > > > > > > > > > > > > So 84 might be the current status. That would m= ean that someone at > > > > > > > > > > > Srarlink might be paying some attention, but it is = a long way from what > > > > > > > > > > > Musk implied. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > PS: I forget the number of the R=46C, but the n= umber of packets queued on > > > > > > > > > > > an egress link should be chosen by taking the hardw= are bottleneck > > > > > > > > > > > throughput of any path, combined with an end-to-end= Internet underlying > > > > > > > > > > > delay of about 10 msec. to account for hops between= source and destination. > > > > > > > > > > > Lets say Starlink allocates 50 Mb/sec to each custo= mer, packets are limited > > > > > > > > > > > to 10,000 bits (1500 * 8), so the outbound queues s= hould be limited to > > > > > > > > > > > about 0.01 * 50,000,000 / 10,000, which comes out t= o about 250 packets from > > > > > > > > > > > each terminal of buffering, total, in the path from= terminal to public > > > > > > > > > > > Internet, assuming the connection to the public Int= ernet is not a problem. > > > > > > > > > > > > =5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F= =5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F= =5F=5F=5F=5F=5F > > > > > > > > > > > > Starlink mailing list > > > > > > > > > > > > Starlink=40lists.bufferbloat.net > > > > > > > > > > > > > > > > > > > > > > > https://secure-web.cisco.com/1sNc=5F-1HhGCW7xdirt=5F= lAoAy5Nn5T6UA85Scjn5BR7QHXtumhrf6RKn78SuRJG7DUKI3duggU9g6hJKW-Ze07HTczYqB= 9mBpIeALqk5drQ7nMvM8K7JbWfUbPR7JSNrI75UjiNXQk0wslBfoOTvkMlRj5eMOZhps7DMGB= RQTVAeTd5vwXoQtDgS6zLCcJkrcO2S9MRSCC4f1I17SzgQJIwqo3LEwuN6lD-pkX0M=46LqGr= 2zzsHw5eapd-VBlHu5reC4-OEn2zHkb7HNzS1pcue=466tsUE1v=46RsWs2SIOwU5MvbKe3J3= Q6NRQ40cHI1AGd-i/https://lists.bufferbloat.net/listinfo/starlink > > > > > > > > > > > > > > > > > > > > > > > > =5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F= =5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F= =5F=5F=5F=5F=5F > > > > > > > > > > > Starlink mailing list > > > > > > > > > > > Starlink=40lists.bufferbloat.net > > > > > > > > > > > https://lists.bufferbloat.net/listinfo/starlink > > > > > > > > > > > > > > > > > > > > > > > > > > > > =5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F= =5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F= =5F=5F > > > > > > > Starlink mailing list > > > > > > > Starlink=40lists.bufferbloat.net > > > > > > > https://lists.bufferbloat.net/listinfo/starlink --60f1fcc4_1ba026fa_bde9 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline
If we understand shell as =E2=80=9Cgroup of satelli= tes at a certain altitude range=E2=80=9D, there is not much point in link= ing between shells if you can link within one shell and orbital plane, an= d that plane has at least one satellite within range of a gateway. I coul= d be proven wrong, but IMHO the first generation of links are meant of in= tra-plane, and maybe at a stretch cross-plane to the next plane East or W= est.

The only way to eventually go is optical links to the ground too, as R=46= will only get you so far. At that stage, every shell will have its own o= ptical links to the ground, with gateways placed in areas with little ave= rage cloud cover.

Best,

Mike
On Jul 16, 2021, 23:30 +0200, David= Lang <david=40lang.hm>, wrote:
at satellite distances, you need to adjust your vertical direct= ion depending on
how far away the satellite you are talking to is, even if it's at the sam= e
altitude

the difference between shells that are only a few KM apart is less than t= he
angles that you could need to satellites in the same shell further away.<= br />
David Lang

On =46ri, 16 Jul 2021, Mike Puchol wrote:

Date: =46ri, 16 Jul 2021 22:57:14 +0200
=46rom: Mike Puchol <mike=40starlink.sx>
To: David Lang <david=40lang.hm>
Cc: Nathan Owens <nathan=40nathan.io>,
=22starlink=40lists.bufferbloat.net=22 <starlink=40lists.bufferbloat.n= et>,
David P. Reed <dpreed=40deepplum.com>
Subject: Re: =5BStarlink=5D Starlink and bufferbloat status=3F

Correct. A mirror tracking head that turns around the perpendicular to th= e satellite path allows you to track satellites in the same plane, in fro= nt or behind, when they change altitude by a few kilometers as part of or= bital adjustments or collision avoidance. To have a fully gimbaled head t= hat can track any satellite in any direction (and at any relative velocit= y=21) is a totally different problem. I could see satellites linked to th= e next longitudinal plane apart from those on the same plane, but cross-p= lane when one is ascending and the other descending is way harder. The ne= xt shells will be at lower altitudes, around 300-350km, and they have als= o stated they want to go for higher shells at 1000+ km.

Best,

Mike
On Jul 16, 2021, 20:48 +0200, David Lang <david=40lang.hm>, wrote:<= br />
I expect the lasers to have 2d gimbles, whi= ch lets them track most things in
their field of view. Remember that Starlink has compressed their orbital = planes,
they are going to be running almost everything in the 550km range (500-60= 0km
IIRC) and have almost entirely eliminated the =7E1000km planes

David Lang

On =46ri, 16 Jul 2021,
Mike Puchol wrote:

Date: =46ri, 16 Jul 2021 19:42:55 +0200
=46rom: Mike Puchol <mike=40starlink.sx>
To: David Lang <david=40lang.hm>
Cc: Nathan Owens <nathan=40nathan.io>,
=22starlink=40lists.bufferbloat.net=22 <starlink=40lists.bufferbloat.n= et>,
David P. Reed <dpreed=40deepplum.com>
Subject: Re: =5BStarlink=5D Starlink and bufferbloat status=3F

True, but we are then assuming that the optical links are a mesh between = satellites in the same plane, plus between planes. =46rom an engineering = problem point of view, keeping optical links in-plane only makes the syst= em extremely simpler (no full =46OV gimbals with the optical train in the= m, for example), and it solves the issue, as it is highly likely that at = least one satellite in any given plane will be within reach of a gateway.=

Routing to an arbitrary gateway may involve passing via intermediate gate= ways, ground segments, and even using terminals as a hopping point.
=
Best,

Mike
On Jul 16, 2021, 19:38 +0200, David Lang <david=40lang.hm>, wrote:<= br />
the speed of light in a vaccum is significa= ntly better than the speed of light
in fiber, so if you are doing a cross country hop, terminal -> sat -&g= t; sat -> sat
-> ground station (especially if the ground station is in the target d= atacenter)
can be faster than terminal -> sat -> ground station -> cross-co= untry fiber,
even accounting for the longer distance at 550km altitude than at ground = level.

This has interesting implications for supplementing/replacing undersea ca= bles as
the sats over the ocean are not going to be heavily used, dedicated groun= d
stations could be setup that use sats further offshore than normal (and a= re
shielded from sats over land) to leverage the system without interfering<= br /> significantly with more 'traditional' uses

David Lang

On =46ri, 16 Jul 2021, Mike Puchol wrote:

Date: =46ri, 16 Jul 2021 19:31:37 +0200
=46rom: Mike Puchol <mike=40starlink.sx>
To: David Lang <david=40lang.hm>, Nathan Owens <nathan=40nathan.= io>
Cc: =22starlink=40lists.bufferbloat.net=22 <starlink=40lists.bufferblo= at.net>,
David P. Reed <dpreed=40deepplum.com>
Subject: Re: =5BStarlink=5D Starlink and bufferbloat status=3F

Satellite optical links are useful to extend coverage to areas where you = don=E2=80=99t have gateways - thus, they will introduce additional latenc= y compared to two space segment hops (terminal to satellite -> satelli= te to gateway). If you have terminal to satellite, two optical hops, then= final satellite to gateway, you will have more latency, not less.

We are being =E2=80=9Csold=E2=80=9D optical links for what they are not I= MHO.

Best,

Mike
On Jul 16, 2021, 19:29 +0200, Nathan Owens <nathan=40nathan.io>, wr= ote:
As there are more satellites, the up down t= ime will get closer to 4-5ms rather then the =7E7ms you list

Possibly, if you do steering to always jump to the lowest latency satelli= te.

with laser relays in orbit, and terminal to= terminal routing in orbit, there is the potential for the theoretical mi= nimum to tend lower
Maybe for certain users really in the middle of nowhere, but I did the be= st-case math for =22bent pipe=22 in Seattle area, which is as good as it = gets.

On =46ri, Jul 16, 2021 at 10:24 AM David La= ng <david=40lang.hm> wrote:
hey, it's a good attitude to have :-)
=
Elon tends to set 'impossible' goals, miss the timeline a bit, and come v= ery
close to the goal, if not exceed it.

As there are more staellites, the up down time will get closer to 4-5ms r= ather
then the =7E7ms you list, and with laser relays in orbit, and terminal to= terminal
routing in orbit, there is the potential for the theoretical minimum to t= end
lower, giving some headroom for other overhead but still being in the 20m= s
range.

David Lang

&=23160; On =46ri, 16 Jul 2021, Nathan Owens wrote:

Elon said =22foolish packet routing=22 for = things over 20ms=21 Which seems crazy
if you do some basic math:

&=23160; &=23160;- Sat to User Terminal distance: 550-950km air/vacuum: 1= .9 - 3.3ms
&=23160; &=23160;- Sat to GW distance: 550-950km air/vacuum: 1.9 - 3.3ms<= br /> &=23160; &=23160;- GW to PoP Distance: 50-800km fiber: 0.25 - 4ms
&=23160; &=23160;- PoP to Internet Distance: 50km fiber: 0.25 - 0.5ms
&=23160; &=23160;- Total one-way delay: 4.3 - 11.1ms
&=23160; &=23160;- Theoretical minimum RTT: 8.6ms - 22.2ms, call it 15.4m= s

This includes no transmission delay, queuing delay,
processing/fragmentation/reassembly/etc, and no time-division multiplexin= g.

On =46ri, Jul 16, 2021 at 10:09 AM David Lang <david=40lang.hm> wro= te:

I think it depends on if you are looking at= datacenter-to-datacenter
latency of
home to remote datacenter latency :-)

my rule of thumb for cross US ping time has been 80-100ms latency (but it's been
a few years since I tested it).

I note that an article I saw today said that Elon is saying that latency<= br /> will
improve significantly in the near future, that up/down latency is =7E20ms=
and the
additional delays pushing it to the 80ms range are 'stupid packet routing= '
problems that they are working on.

If they are still in that level of optimization, it doesn't surprise me that
they haven't really focused on the bufferbloat issue, they have more
obvious
stuff to fix first.

David Lang


&=23160; &=23160;On =46ri, 16 Jul 2021, Wheelock, Ian wrote:

Date: =46ri, 16 Jul 2021 10:21:52 +0000
=46rom: =22Wheelock, Ian=22 <ian.wheelock=40commscope.com>
To: David Lang <david=40lang.hm>, David P. Reed <dpreed=40deeppl= um.com>
Cc: =22starlink=40lists.bufferbloat.net=22 <starlink=40lists.bufferblo= at.net>
Subject: Re: =5BStarlink=5D Starlink and bufferbloat status=3F

Hi David
In terms of the Latency that David (Reed) mentioned for California to
Massachusetts of about 17ms over the public internet, it seems a bit fast= er
than what I would expect. My own traceroute via my VDSL link shows 14ms just to get out of the operator network.

https://www.wondernetwork.com&=23160; is a handy tool for checking geogra= phic
ping perf between cities, and it shows a min of about 66ms for pings
between Boston and San Diego
https://wondernetwork.com/pings/boston/San%20Diego (so about 33ms for
1-way transfer).

Distance wise this is about 4,100 KM (2,500 M), and =402/3 speed of light=
(through a pure fibre link of that distance) the propagation time is just=
over 20ms. If the network equipment between the Boston and San Diego is factored in, with some buffering along the way, 33ms does seem quite
reasonable over the 20ms for speed of light in fibre for that 1-way trans= fer

-Ian Wheelock

=46rom: Starlink <starlink-bounces=40lists.bufferbloat.net> on beha= lf of
David Lang <david=40lang.hm>
Date: =46riday 9 July 2021 at 23:59
To: =22David P. Reed=22 <dpreed=40deepplum.com>
Cc: =22starlink=40lists.bufferbloat.net=22 <starlink=40lists.bufferblo= at.net>
Subject: Re: =5BStarlink=5D Starlink and bufferbloat status=3F

IIRC, the definition of 'low latency' for the =46CC was something like
100ms, and Musk was predicting <40ms. roughly competitive with landlin= es,
and worlds better than geostationary satellite (and many
External (mailto:david=40lang.hm)

https://shared.outlook.inky.com/report=3Fid=3DY29tbXNjb3BlL2lhbi53aGVlbG9= ja0Bjb21tc2NvcGUuY29tL2I1Mz=46jZDA4OTZmMWI0Yzc5NzdiOTIzNmY3MTAzM2MxLzE2Mj= U4NzE1NDkuNjU=3D=23key=3D19e8545676e28e577c813de83a4cf1dc
&=23160; https://www.inky.com/banner-faq/&=23160; https://www.inky.com

IIRC, the definition of 'low latency' for the =46CC was something like
100ms, and
Musk was predicting <40ms.

roughly competitive with landlines, and worlds better than geostationary<= br /> satellite (and many wireless ISPs)

but when doing any serious testing of latency, you need to be wired to
the
router, wifi introduces so much variability= that it swamps the signal.

David Lang

On =46ri, 9 Jul 2021, David P. Reed wrote:

Date: =46ri, 9 Jul 2021 14:40:01 -0400 (EDT= )
=46rom: David P. Reed <dpreed=40deepplum.com>
To: starlink=40lists.bufferbloat.net
Subject: =5BStarlink=5D Starlink and bufferbloat status=3F


Early measurements of performance of Starlink have shown significant
bufferbloat, as Dave Taht has shown.

But...&=23160; Starlink is a moving target. The bufferbloat isn't a hardw= are
issue, it should be completely manageable, starting by simple firmware changes inside the Starlink system itself. =46or example, implementing fq=5Fcodel so that bottleneck links just drop packets according to the Be= st
Practices R=46C,

So I'm hoping this has improved since Dave's measurements. How much has
it improved=3F What's the current maximum packet latency under full
= load,&=23160; Ive heard anecdotally that a friend of a friend gets 84 mse= c. *ping
times under full load*, but he wasn't using flent or some other measureme= nt
tool of good quality that gives a true number.

84 msec is not great - it's marginal for Zoom quality experience (you
want latencies significantly less than 100 msec. as a rule of thumb for teleconferencing quality). But it is better than Dave's measurements show= ed.

Now Musk bragged that his network was =22low latency=22 unlike other high=
speed services, which means low end-to-end latency.&=23160; That got him<= br /> permission from the =46CC to operate Starlink at all. His number was, I think, < 5 msec. 84 is a lot more than 5. (I didn't believe 5, because= he
probably meant just the time from the ground station to the terminal
through the satellite. But I regularly get 17 msec. between California an= d
Massachusetts over the public Internet)

So 84 might be the current status. That would mean that someone at
<= /blockquote>
Srarlink might be paying some attention, but it is a long way from what Musk implied.


PS: I forget the number of the R=46C, but the number of packets queued on=
an egress link should be chosen by taking the hardware bottleneck
throughput of any path, combined with an end-to-end Internet underlying delay of about 10 msec. to account for hops between source and destinatio= n.
Lets say Starlink allocates 50 Mb/sec to each customer, packets are limit= ed
to 10,000 bits (1500 * 8), so the outbound queues should be limited to about 0.01 * 50,000,000 / 10,000, which comes out to about 250 packets fr= om
each terminal of buffering, total, in the path from terminal to public Internet, assuming the connection to the public Internet is not a problem= .
=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F= =5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F= =5F=5F=5F=5F=5F=5F=5F
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