From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from vsmx001.dclux.xion.oxcs.net (vsmx001.dclux.xion.oxcs.net [185.74.65.81]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 6EE943CB38 for ; Fri, 16 Jul 2021 16:57:27 -0400 (EDT) Received: from proxy-1.proxy.oxio.ns.xion.oxcs.net (proxy-1.proxy.oxio.ns.xion.oxcs.net [83.61.18.4]) by mx-out.dclux.xion.oxcs.net (Postfix) with SMTP id A462E8C0A5B; Fri, 16 Jul 2021 20:57:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=dclux.xion.oxcs.net; s=mail1; t=1626469046; bh=PdGl16x33sFrLJLua5evZpivyisNdaVswbuXEux+8X4=; h=Date:From:To:Cc:In-Reply-To:References:Subject:From; b=OHwpFWGd3rEpCynN4eyTrMz2u/pyx0FhYE6Vq5vskIM1ASZqew4CMWgn7eahaEQdb LIl4tiLr02Cv4ApmKA0Et7ADEss+H13+4LitW8uBMwogh5o4OHkGj9XfJ6UOrPdm9d HiVQxUvimyIpBkppkhhmhSM4SS7bo28dJZ7ZnpLyyUX09vaS9IFV45KYHSXdukGl0y THduWEoscfvZo6ylmP9OqOX3smwOVuONz5vx1Cf0/mT5FCbDLtv/MHtTl6NZpfdw8C n4+SlC60Jgv5lKzI6r+l1O7wpYAUY4ihdaEVq4cgQG4zgB4qzGVDA8bPWARdE5EoyH IJsFQizophbAQ== Date: Fri, 16 Jul 2021 22:57:14 +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: e6c70355-a16c-4722-9bca-9f6a1bce9f6c@Spark MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="60f1f2af_749abb43_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 20:57:27 -0000 --60f1f2af_749abb43_bde9 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline 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 , wrote: > I expect the lasers to have 2d gimbles, which lets them track most thin= gs in > their field of view. Remember that Starlink has compressed their orbita= l 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 betw= een satellites in the same plane, plus between planes. =46rom an engineer= ing problem point of view, keeping optical links in-plane only makes the = system extremely simpler (no full =46OV gimbals with the optical train 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 gate= way. > > > > Routing to an arbitrary gateway may involve passing via intermediate = gateways, ground segments, and even using terminals as a hopping point. > > > > Best, > > > > Mike > > On Jul 16, 2021, 19:38 +0200, David Lang , wrote: > > > the speed of light in a vaccum is significantly better than the spe= ed 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 targe= t datacenter) > > > can be faster than terminal -> sat -> ground station -> cross-count= ry fiber, > > > even accounting for the longer distance at 550km altitude than at g= round level. > > > > > > This has interesting implications for supplementing/replacing under= sea cables as > > > the sats over the ocean are not going to be heavily used, dedicated= ground > > > stations could be setup that use sats further offshore than normal = (and are > > > shielded from sats over land) to leverage the system without interf= ering > > > 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 areas wh= ere you don=E2=80=99t have gateways - thus, they will introduce additiona= l latency compared to two space segment hops (terminal to satellite -> sa= tellite 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 a= re 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 close= r to 4-5ms rather then the =7E7ms you list > > > > > > > > > > Possibly, if you do steering to always jump to the lowest laten= cy satellite. > > > > > > > > > > > with laser relays in orbit, and terminal to terminal routing = in orbit, there is the potential for the theoretical minimum to tend lowe= r > > > > > Maybe for certain users really in the middle of nowhere, but I = did the best-case math for =22bent pipe=22 in Seattle area, which is as g= ood 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 b= it, and come very > > > > > > > close to the goal, if not exceed it. > > > > > > > > > > > > > > As there are more staellites, the up down time will get clo= ser to 4-5ms rather > > > > > > > then the =7E7ms you list, and with laser relays in orbit, a= nd terminal to terminal > > > > > > > routing in orbit, there is the potential for the theoretica= l minimum to tend > > > > > > > lower, giving some headroom for other overhead but still be= ing in the 20ms > > > > > > > range. > > > > > > > > > > > > > > David Lang > > > > > > > > > > > > > > =C2=A0 On =46ri, 16 Jul 2021, Nathan Owens wrote: > > > > > > > > > > > > > > > Elon said =22foolish packet routing=22 for things over 20= ms=21 Which seems crazy > > > > > > > > if you do some basic math: > > > > > > > > > > > > > > > > =C2=A0 =C2=A0- Sat to User Terminal distance: 550-950km a= ir/vacuum: 1.9 - 3.3ms > > > > > > > > =C2=A0 =C2=A0- Sat to GW distance: 550-950km air/vacuum: = 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 - 22.2ms, c= all it 15.4ms > > > > > > > > > > > > > > > > This includes no transmission delay, queuing delay, > > > > > > > > processing/fragmentation/reassembly/etc, and no time-divi= sion multiplexing. > > > > > > > > > > > > > > > > On =46ri, Jul 16, 2021 at 10:09 AM David Lang wrote: > > > > > > > > > > > > > > > > > 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 80-100= ms latency (but > > > > > > > > > it's been > > > > > > > > > a few years since I tested it). > > > > > > > > > > > > > > > > > > I note that an article I saw today said that Elon is sa= ying that latency > > > > > > > > > will > > > > > > > > > improve significantly in the near future, that up/down = latency is =7E20ms > > > > > > > > > and the > > > > > > > > > additional delays pushing it to the 80ms range are 'stu= pid packet routing' > > > > > > > > > problems that they are working on. > > > > > > > > > > > > > > > > > > If they are still in that level of optimization, it doe= sn't surprise me > > > > > > > > > that > > > > > > > > > they haven't really focused on the bufferbloat issue, t= hey have more > > > > > > > > > obvious > > > > > > > > > stuff to fix first. > > > > > > > > > > > > > > > > > > David Lang > > > > > > > > > > > > > > > > > > > > > > > > > > > =C2=A0 =C2=A0On =46ri, 16 Jul 2021, Wheelock, Ian wrote= : > > > > > > > > > > > > > > > > > > > Date: =46ri, 16 Jul 2021 10:21:52 +0000 > > > > > > > > > > =46rom: =22Wheelock, Ian=22 > > > > > > > > > > To: David Lang , David P. Reed > > > > > > > > > > Cc: =22starlink=40lists.bufferbloat.net=22 > > > > > > > > > > Subject: Re: =5BStarlink=5D Starlink and bufferbloat = status=3F > > > > > > > > > > > > > > > > > > > > Hi David > > > > > > > > > > In terms of the Latency that David (Reed) mentioned f= or California to > > > > > > > > > Massachusetts of about 17ms over the public internet, i= t 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 tool f= or checking geographic > > > > > > > > > ping perf between cities, and it shows a min of about 6= 6ms 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 =40= 2/3 speed of light > > > > > > > > > (through a pure fibre link of that distance) the propag= ation 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 do= es seem quite > > > > > > > > > reasonable over the 20ms for speed of light in fibre fo= r 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 bufferbloat = status=3F > > > > > > > > > > > > > > > > > > > > IIRC, the definition of 'low latency' for the =46CC w= as something like > > > > > > > > > 100ms, and Musk was predicting <40ms. roughly competiti= ve with landlines, > > > > > > > > > and worlds better than geostationary satellite (and man= y > > > > > > > > > > External (mailto:david=40lang.hm) > > > > > > > > > > > > > > > > > > > https://shared.outlook.inky.com/report=3Fid=3DY29tbXNjb= 3BlL2lhbi53aGVlbG9ja0Bjb21tc2NvcGUuY29tL2I1Mz=46jZDA4OTZmMWI0Yzc5NzdiOTIz= NmY3MTAzM2MxLzE2MjU4NzE1NDkuNjU=3D=23key=3D19e8545676e28e577c813de83a4cf1= dc > > > > > > > > > =C2=A0 https://www.inky.com/banner-faq/=C2=A0 https://w= ww.inky.com > > > > > > > > > > > > > > > > > > > > IIRC, the definition of 'low latency' for the =46CC w= as something like > > > > > > > > > 100ms, and > > > > > > > > > > Musk was predicting <40ms. > > > > > > > > > > > > > > > > > > > > roughly competitive with landlines, and worlds better= than geostationary > > > > > > > > > > satellite (and many wireless ISPs) > > > > > > > > > > > > > > > > > > > > but when doing any serious testing of latency, you ne= ed to be wired to > > > > > > > > > the > > > > > > > > > > router, wifi introduces so much variability that it s= wamps 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 bufferbloat st= atus=3F > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Early measurements of performance of Starlink have = shown significant > > > > > > > > > bufferbloat, as Dave Taht has shown. > > > > > > > > > > > > > > > > > > > > > > But...=C2=A0 Starlink is a moving target. The buffe= rbloat isn't a hardware > > > > > > > > > issue, it should be completely manageable, starting by = simple firmware > > > > > > > > > changes inside the Starlink system itself. =46or exampl= e, implementing > > > > > > > > > fq=5Fcodel so that bottleneck links just drop packets a= ccording to the Best > > > > > > > > > Practices R=46C, > > > > > > > > > > > > > > > > > > > > > > So I'm hoping this has improved since Dave's measur= ements. How much has > > > > > > > > > it improved=3F What's the current maximum packet latenc= y under full > > > > > > > > > load,=C2=A0 Ive heard anecdotally that a friend of a fr= iend gets 84 msec. *ping > > > > > > > > > times under full load*, but he wasn't using flent or so= me other measurement > > > > > > > > > tool of good quality that gives a true number. > > > > > > > > > > > > > > > > > > > > > > 84 msec is not great - it's marginal for Zoom quali= ty experience (you > > > > > > > > > want latencies significantly less than 100 msec. as a r= ule of thumb for > > > > > > > > > teleconferencing quality). But it is better than Dave's= measurements showed. > > > > > > > > > > > > > > > > > > > > > > Now Musk bragged that his network was =22low latenc= y=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 all. H= is number was, I > > > > > > > > > think, < 5 msec. 84 is a lot more than 5. (I didn't bel= ieve 5, because he > > > > > > > > > probably meant just the time from the ground station to= the terminal > > > > > > > > > through the satellite. But I regularly get 17 msec. bet= ween California and > > > > > > > > > Massachusetts over the public Internet) > > > > > > > > > > > > > > > > > > > > > > So 84 might be the current status. That would mean = that someone at > > > > > > > > > Srarlink might be paying some attention, but it is a lo= ng way from what > > > > > > > > > Musk implied. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > PS: I forget the number of the R=46C, but the numbe= r 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 Int= ernet underlying > > > > > > > > > delay of about 10 msec. to account for hops between sou= rce and destination. > > > > > > > > > Lets say Starlink allocates 50 Mb/sec to each customer,= packets are limited > > > > > > > > > to 10,000 bits (1500 * 8), so the outbound queues shoul= d be limited to > > > > > > > > > about 0.01 * 50,000,000 / 10,000, which comes out to ab= out 250 packets from > > > > > > > > > each terminal of buffering, total, in the path from ter= minal to public > > > > > > > > > Internet, assuming the connection to the public Interne= t 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=5FlAo= Ay5Nn5T6UA85Scjn5BR7QHXtumhrf6RKn78SuRJG7DUKI3duggU9g6hJKW-Ze07HTczYqB9mB= pIeALqk5drQ7nMvM8K7JbWfUbPR7JSNrI75UjiNXQk0wslBfoOTvkMlRj5eMOZhps7DMGBRQT= VAeTd5vwXoQtDgS6zLCcJkrcO2S9MRSCC4f1I17SzgQJIwqo3LEwuN6lD-pkX0M=46LqGr2zz= sHw5eapd-VBlHu5reC4-OEn2zHkb7HNzS1pcue=466tsUE1v=46RsWs2SIOwU5MvbKe3J3Q6N= RQ40cHI1AGd-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 --60f1f2af_749abb43_bde9 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline
Correct. A mirror tracking head that turns around t= he perpendicular to the satellite path allows you to track satellites in = the same plane, in front or behind, when they change altitude by a few ki= lometers as part of orbital adjustments or collision avoidance. To have a= fully gimbaled head that can track any satellite in any direction (and a= t any relative velocity=21) is a totally different problem. I could see s= atellites linked to the next longitudinal plane apart from those on the s= ame plane, but cross-plane when one is ascending and the other descending= is way harder. The next shells will be at lower altitudes, around 300-35= 0km, 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 <david=40lang.hm>, wrote:
I expect the lasers to have 2d gimbles, which lets them track m= ost 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= .
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