[Starlink] Starlink and bufferbloat status?

Fri Jul 16 13:35:30 EDT 2021

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 <mike at starlink.sx> 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 <nathan at nathan.io>, 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 <david at lang.hm> 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 <david at lang.hm> 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" <ian.wheelock at commscope.com>
>> >>> To: David Lang <david at lang.hm>, David P. Reed <dpreed at deepplum.com>
>> >>> Cc: "starlink at lists.bufferbloat.net" <starlink at 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 <starlink-bounces at lists.bufferbloat.net> on behalf of
>> >> David Lang <david at lang.hm>
>> >>> Date: Friday 9 July 2021 at 23:59
>> >>> To: "David P. Reed" <dpreed at deepplum.com>
>> >>> Cc: "starlink at lists.bufferbloat.net" <starlink at 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 at 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 <dpreed at deepplum.com>
>> >>>> To: starlink at 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 at lists.bufferbloat.net
>> >>>
>> >>
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>> >>>
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>> >>
>> >
>>
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