The other case where they could provide benefit is very long distance paths --- NY to Tokyo, Johannesburg to London, etc... but presumably at high cost, as the capacity will likely be much lower than submarine cables. On Fri, Jul 16, 2021 at 10:31 AM Mike Puchol wrote: > Satellite optical links are useful to extend coverage to areas where you > don’t have gateways - thus, they will introduce additional latency compared > to two space segment hops (terminal to satellite -> satellite 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 “sold” optical links for what they 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 closer to 4-5ms > rather then the ~7ms you list > > Possibly, if you do steering to always jump to the lowest latency > satellite. > > > with laser relays in orbit, and terminal to terminal routing in orbit, > there is the potential for the theoretical minimum to tend lower > Maybe for certain users really in the middle of nowhere, but I did the > best-case math for "bent pipe" in Seattle area, which is as good as it gets. > > On Fri, 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 ~7ms you list, and with laser relays in orbit, and terminal to >> terminal >> routing in orbit, there is the potential for the theoretical minimum to >> tend >> lower, giving some headroom for other overhead but still being in the 20ms >> range. >> >> David Lang >> >> On Fri, 16 Jul 2021, Nathan Owens wrote: >> >> > Elon said "foolish packet routing" for things over 20ms! Which seems >> crazy >> > if you do some basic math: >> > >> > - Sat to User Terminal distance: 550-950km air/vacuum: 1.9 - 3.3ms >> > - Sat to GW distance: 550-950km air/vacuum: 1.9 - 3.3ms >> > - GW to PoP Distance: 50-800km fiber: 0.25 - 4ms >> > - PoP to Internet Distance: 50km fiber: 0.25 - 0.5ms >> > - Total one-way delay: 4.3 - 11.1ms >> > - Theoretical minimum RTT: 8.6ms - 22.2ms, call it 15.4ms >> > >> > This includes no transmission delay, queuing delay, >> > processing/fragmentation/reassembly/etc, and no time-division >> multiplexing. >> > >> > On Fri, 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 80-100ms 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 >> >> will >> >> improve significantly in the near future, that up/down latency is ~20ms >> >> 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 >> >> >> >> >> >> On Fri, 16 Jul 2021, Wheelock, Ian wrote: >> >> >> >>> Date: Fri, 16 Jul 2021 10:21:52 +0000 >> >>> From: "Wheelock, Ian" >> >>> To: David Lang , David P. Reed >> >>> Cc: "starlink@lists.bufferbloat.net" >> >>> Subject: Re: [Starlink] Starlink and bufferbloat status? >> >>> >> >>> 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 >> 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 is a handy tool for checking >> geographic >> >> 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 @2/3 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 >> transfer >> >>> >> >>> -Ian Wheelock >> >>> >> >>> From: Starlink on behalf of >> >> David Lang >> >>> Date: Friday 9 July 2021 at 23:59 >> >>> To: "David P. Reed" >> >>> Cc: "starlink@lists.bufferbloat.net" >> >>> Subject: Re: [Starlink] Starlink and bufferbloat status? >> >>> >> >>> IIRC, the definition of 'low latency' for the FCC was something like >> >> 100ms, and Musk was predicting <40ms. roughly competitive with >> landlines, >> >> and worlds better than geostationary satellite (and many >> >>> External (mailto:david@lang.hm) >> >>> >> >> >> https://shared.outlook.inky.com/report?id=Y29tbXNjb3BlL2lhbi53aGVlbG9ja0Bjb21tc2NvcGUuY29tL2I1MzFjZDA4OTZmMWI0Yzc5NzdiOTIzNmY3MTAzM2MxLzE2MjU4NzE1NDkuNjU=#key=19e8545676e28e577c813de83a4cf1dc >> >> https://www.inky.com/banner-faq/ https://www.inky.com >> >>> >> >>> IIRC, the definition of 'low latency' for the FCC was 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 need to be wired to >> >> the >> >>> router, wifi introduces so much variability that it swamps the signal. >> >>> >> >>> David Lang >> >>> >> >>> On Fri, 9 Jul 2021, David P. Reed wrote: >> >>> >> >>>> Date: Fri, 9 Jul 2021 14:40:01 -0400 (EDT) >> >>>> From: David P. Reed >> >>>> To: starlink@lists.bufferbloat.net >> >>>> Subject: [Starlink] Starlink and bufferbloat status? >> >>>> >> >>>> >> >>>> Early measurements of performance of Starlink have shown significant >> >> bufferbloat, as Dave Taht has shown. >> >>>> >> >>>> But... Starlink is a moving target. The bufferbloat isn't a hardware >> >> issue, it should be completely manageable, starting by simple firmware >> >> changes inside the Starlink system itself. For example, implementing >> >> fq_codel so that bottleneck links just drop packets according to the >> Best >> >> Practices RFC, >> >>>> >> >>>> So I'm hoping this has improved since Dave's measurements. How much >> has >> >> it improved? What's the current maximum packet latency under full >> >> load, Ive heard anecdotally that a friend of a friend gets 84 msec. >> *ping >> >> times under full load*, but he wasn't using flent or some other >> measurement >> >> 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 >> showed. >> >>>> >> >>>> Now Musk bragged that his network was "low latency" unlike other high >> >> speed services, which means low end-to-end latency. That got him >> >> permission from the FCC 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 >> 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 long way from what >> >> Musk implied. >> >>>> >> >>>> >> >>>> PS: I forget the number of the RFC, 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 >> destination. >> >> Lets say Starlink allocates 50 Mb/sec to each customer, packets are >> limited >> >> 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 >> from >> >> each terminal of buffering, total, in the path from terminal to public >> >> Internet, assuming the connection to the public Internet is not a >> problem. >> >>> _______________________________________________ >> >>> Starlink mailing list >> >>> Starlink@lists.bufferbloat.net >> >>> >> >> >> https://secure-web.cisco.com/1sNc_-1HhGCW7xdirt_lAoAy5Nn5T6UA85Scjn5BR7QHXtumhrf6RKn78SuRJG7DUKI3duggU9g6hJKW-Ze07HTczYqB9mBpIeALqk5drQ7nMvM8K7JbWfUbPR7JSNrI75UjiNXQk0wslBfoOTvkMlRj5eMOZhps7DMGBRQTVAeTd5vwXoQtDgS6zLCcJkrcO2S9MRSCC4f1I17SzgQJIwqo3LEwuN6lD-pkX0MFLqGr2zzsHw5eapd-VBlHu5reC4-OEn2zHkb7HNzS1pcueF6tsUE1vFRsWs2SIOwU5MvbKe3J3Q6NRQ40cHI1AGd-i/https://lists.bufferbloat.net/listinfo/starlink >> >>> >> >>> _______________________________________________ >> >> Starlink mailing list >> >> Starlink@lists.bufferbloat.net >> >> https://lists.bufferbloat.net/listinfo/starlink >> >> >> > >> > _______________________________________________ > Starlink mailing list > Starlink@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/starlink > >