[Starlink] Starlink and bufferbloat status?

Sun Jul 18 21:34:31 EDT 2021

No requirement for layer3 for that. I’d bet money they’ll keep L3 out of
space.

nb

On Sun, Jul 18, 2021 at 8:20 PM David Lang <david at lang.hm> wrote:

> Elon is talking about a viable path in the future being dishy - sat - sat
> -
> dishy
>
> They aren't there yet, but they are sure planning on it
>
> David Lang
>
> On Sun, 18 Jul 2021, Nick Buraglio wrote:
>
> > We keep saying “route”. What do we actually mean from a network stack
> > perspective? Are we talking about relaying light / frames / electric or
> do
> > we mean actual packet routing, because there are obviously a lot of
> > important distinctions there.
> > I’m willing to bet that there is no routing (as in layer 3 packet
> routing)
> > at all except the Dish NAT all the way into their peering data center.
> The
> > ground stations are very likely RF to fiber wave division back to a
> carrier
> > hotel with no L3 buffering at all. That keeps latency very low (think
> O-E-O
> > and E-O transitions) and moves L3 buffering to two locations and keeps
> the
> > terrestrial network very easy to make redundant (optical protection,
> etc.).
> >
> > nb
> >
> > On Fri, Jul 16, 2021 at 12:39 PM Jonathan Bennett <
> > jonathanbennett at hackaday.com> wrote:
> >
> >>
> >>
> >> On Fri, Jul 16, 2021, 12:35 PM Nathan Owens <nathan at nathan.io> wrote:
> >>
> >>> 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.
> >>>
> >>>>
> >> Or traffic between Starlink customers. A video call between me and
> someone
> >> else on the Starlink network is going to be drastically better if it can
> >> route over the sats.
> >>
> >>>
> >>>> 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
> >>>>>>>>
> >>>>>>>
> >>>>>
> https://secure-web.cisco.com/1sNc_-1HhGCW7xdirt_lAoAy5Nn5T6UA85Scjn5BR7QHXtumhrf6RKn78SuRJG7DUKI3duggU9g6hJKW-Ze07HTczYqB9mBpIeALqk5drQ7nMvM8K7JbWfUbPR7JSNrI75UjiNXQk0wslBfoOTvkMlRj5eMOZhps7DMGBRQTVAeTd5vwXoQtDgS6zLCcJkrcO2S9MRSCC4f1I17SzgQJIwqo3LEwuN6lD-pkX0MFLqGr2zzsHw5eapd-VBlHu5reC4-OEn2zHkb7HNzS1pcueF6tsUE1vFRsWs2SIOwU5MvbKe3J3Q6NRQ40cHI1AGd-i/https://lists.bufferbloat.net/listinfo/starlink
> >>>>>>>>
> >>>>>>>> _______________________________________________
> >>>>>>> Starlink mailing list
> >>>>>>> Starlink at lists.bufferbloat.net
> >>>>>>> https://lists.bufferbloat.net/listinfo/starlink
> >>>>>>>
> >>>>>>
> >>>>>
> >>>> _______________________________________________
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> >>>>
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> >>>
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