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 >