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<div dir="auto">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.<br />
<br />
We are being “sold” optical links for what they are not IMHO.</div>
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<div class="matchFont">Best,<br />
<br />
Mike</div>
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<div name="messageReplySection">On Jul 16, 2021, 19:29 +0200, Nathan Owens <nathan@nathan.io>, wrote:<br />
<blockquote type="cite" style="border-left-color: grey; border-left-width: thin; border-left-style: solid; margin: 5px 5px;padding-left: 10px;">
<div dir="ltr">> As there are more satellites, the up down time will get closer to 4-5ms rather then the ~7ms you list<br />
<div><br /></div>
<div>Possibly, if you do steering to always jump to the lowest latency satellite. </div>
<div><br /></div>
<div>> with laser relays in orbit, and terminal to terminal routing in orbit, there is the potential for the theoretical minimum to tend lower<br /></div>
<div>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.<br /></div>
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<div dir="ltr" class="gmail_attr">On Fri, Jul 16, 2021 at 10:24 AM David Lang <<a href="mailto:david@lang.hm">david@lang.hm</a>> wrote:<br /></div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">hey, it's a good attitude to have :-)<br />
<br />
Elon tends to set 'impossible' goals, miss the timeline a bit, and come very<br />
close to the goal, if not exceed it.<br />
<br />
As there are more staellites, the up down time will get closer to 4-5ms rather<br />
then the ~7ms you list, and with laser relays in orbit, and terminal to terminal<br />
routing in orbit, there is the potential for the theoretical minimum to tend<br />
lower, giving some headroom for other overhead but still being in the 20ms<br />
range.<br />
<br />
David Lang<br />
<br />
On Fri, 16 Jul 2021, Nathan Owens wrote:<br />
<br />
> Elon said "foolish packet routing" for things over 20ms! Which seems crazy<br />
> if you do some basic math:<br />
><br />
> - Sat to User Terminal distance: 550-950km air/vacuum: 1.9 - 3.3ms<br />
> - Sat to GW distance: 550-950km air/vacuum: 1.9 - 3.3ms<br />
> - GW to PoP Distance: 50-800km fiber: 0.25 - 4ms<br />
> - PoP to Internet Distance: 50km fiber: 0.25 - 0.5ms<br />
> - Total one-way delay: 4.3 - 11.1ms<br />
> - Theoretical minimum RTT: 8.6ms - 22.2ms, call it 15.4ms<br />
><br />
> This includes no transmission delay, queuing delay,<br />
> processing/fragmentation/reassembly/etc, and no time-division multiplexing.<br />
><br />
> On Fri, Jul 16, 2021 at 10:09 AM David Lang <<a href="mailto:david@lang.hm" target="_blank">david@lang.hm</a>> wrote:<br />
><br />
>> I think it depends on if you are looking at datacenter-to-datacenter<br />
>> latency of<br />
>> home to remote datacenter latency :-)<br />
>><br />
>> my rule of thumb for cross US ping time has been 80-100ms latency (but<br />
>> it's been<br />
>> a few years since I tested it).<br />
>><br />
>> I note that an article I saw today said that Elon is saying that latency<br />
>> will<br />
>> improve significantly in the near future, that up/down latency is ~20ms<br />
>> and the<br />
>> additional delays pushing it to the 80ms range are 'stupid packet routing'<br />
>> problems that they are working on.<br />
>><br />
>> If they are still in that level of optimization, it doesn't surprise me<br />
>> that<br />
>> they haven't really focused on the bufferbloat issue, they have more<br />
>> obvious<br />
>> stuff to fix first.<br />
>><br />
>> David Lang<br />
>><br />
>><br />
>> On Fri, 16 Jul 2021, Wheelock, Ian wrote:<br />
>><br />
>>> Date: Fri, 16 Jul 2021 10:21:52 +0000<br />
>>> From: "Wheelock, Ian" <<a href="mailto:ian.wheelock@commscope.com" target="_blank">ian.wheelock@commscope.com</a>><br />
>>> To: David Lang <<a href="mailto:david@lang.hm" target="_blank">david@lang.hm</a>>, David P. Reed <<a href="mailto:dpreed@deepplum.com" target="_blank">dpreed@deepplum.com</a>><br />
>>> Cc: "<a href="mailto:starlink@lists.bufferbloat.net" target="_blank">starlink@lists.bufferbloat.net</a>" <<a href="mailto:starlink@lists.bufferbloat.net" target="_blank">starlink@lists.bufferbloat.net</a>><br />
>>> Subject: Re: [Starlink] Starlink and bufferbloat status?<br />
>>><br />
>>> Hi David<br />
>>> In terms of the Latency that David (Reed) mentioned for California to<br />
>> Massachusetts of about 17ms over the public internet, it seems a bit faster<br />
>> than what I would expect. My own traceroute via my VDSL link shows 14ms<br />
>> just to get out of the operator network.<br />
>>><br />
>>> <a href="https://www.wondernetwork.com" rel="noreferrer" target="_blank">https://www.wondernetwork.com</a> is a handy tool for checking geographic<br />
>> ping perf between cities, and it shows a min of about 66ms for pings<br />
>> between Boston and San Diego<br />
>> <a href="https://wondernetwork.com/pings/boston/San%20Diego" rel="noreferrer" target="_blank">https://wondernetwork.com/pings/boston/San%20Diego</a> (so about 33ms for<br />
>> 1-way transfer).<br />
>>><br />
>>> Distance wise this is about 4,100 KM (2,500 M), and @2/3 speed of light<br />
>> (through a pure fibre link of that distance) the propagation time is just<br />
>> over 20ms. If the network equipment between the Boston and San Diego is<br />
>> factored in, with some buffering along the way, 33ms does seem quite<br />
>> reasonable over the 20ms for speed of light in fibre for that 1-way transfer<br />
>>><br />
>>> -Ian Wheelock<br />
>>><br />
>>> From: Starlink <<a href="mailto:starlink-bounces@lists.bufferbloat.net" target="_blank">starlink-bounces@lists.bufferbloat.net</a>> on behalf of<br />
>> David Lang <<a href="mailto:david@lang.hm" target="_blank">david@lang.hm</a>><br />
>>> Date: Friday 9 July 2021 at 23:59<br />
>>> To: "David P. Reed" <<a href="mailto:dpreed@deepplum.com" target="_blank">dpreed@deepplum.com</a>><br />
>>> Cc: "<a href="mailto:starlink@lists.bufferbloat.net" target="_blank">starlink@lists.bufferbloat.net</a>" <<a href="mailto:starlink@lists.bufferbloat.net" target="_blank">starlink@lists.bufferbloat.net</a>><br />
>>> Subject: Re: [Starlink] Starlink and bufferbloat status?<br />
>>><br />
>>> IIRC, the definition of 'low latency' for the FCC was something like<br />
>> 100ms, and Musk was predicting <40ms. roughly competitive with landlines,<br />
>> and worlds better than geostationary satellite (and many<br />
>>> External (mailto:<a href="mailto:david@lang.hm" target="_blank">david@lang.hm</a>)<br />
>>><br />
>> <a href="https://shared.outlook.inky.com/report?id=Y29tbXNjb3BlL2lhbi53aGVlbG9ja0Bjb21tc2NvcGUuY29tL2I1MzFjZDA4OTZmMWI0Yzc5NzdiOTIzNmY3MTAzM2MxLzE2MjU4NzE1NDkuNjU=#key=19e8545676e28e577c813de83a4cf1dc" rel="noreferrer" target="_blank">https://shared.outlook.inky.com/report?id=Y29tbXNjb3BlL2lhbi53aGVlbG9ja0Bjb21tc2NvcGUuY29tL2I1MzFjZDA4OTZmMWI0Yzc5NzdiOTIzNmY3MTAzM2MxLzE2MjU4NzE1NDkuNjU=#key=19e8545676e28e577c813de83a4cf1dc</a><br />
>> <a href="https://www.inky.com/banner-faq/" rel="noreferrer" target="_blank">https://www.inky.com/banner-faq/</a> <a href="https://www.inky.com" rel="noreferrer" target="_blank">https://www.inky.com</a><br />
>>><br />
>>> IIRC, the definition of 'low latency' for the FCC was something like<br />
>> 100ms, and<br />
>>> Musk was predicting <40ms.<br />
>>><br />
>>> roughly competitive with landlines, and worlds better than geostationary<br />
>>> satellite (and many wireless ISPs)<br />
>>><br />
>>> but when doing any serious testing of latency, you need to be wired to<br />
>> the<br />
>>> router, wifi introduces so much variability that it swamps the signal.<br />
>>><br />
>>> David Lang<br />
>>><br />
>>> On Fri, 9 Jul 2021, David P. Reed wrote:<br />
>>><br />
>>>> Date: Fri, 9 Jul 2021 14:40:01 -0400 (EDT)<br />
>>>> From: David P. Reed <<a href="mailto:dpreed@deepplum.com" target="_blank">dpreed@deepplum.com</a>><br />
>>>> To: <a href="mailto:starlink@lists.bufferbloat.net" target="_blank">starlink@lists.bufferbloat.net</a><br />
>>>> Subject: [Starlink] Starlink and bufferbloat status?<br />
>>>><br />
>>>><br />
>>>> Early measurements of performance of Starlink have shown significant<br />
>> bufferbloat, as Dave Taht has shown.<br />
>>>><br />
>>>> But... Starlink is a moving target. The bufferbloat isn't a hardware<br />
>> issue, it should be completely manageable, starting by simple firmware<br />
>> changes inside the Starlink system itself. For example, implementing<br />
>> fq_codel so that bottleneck links just drop packets according to the Best<br />
>> Practices RFC,<br />
>>>><br />
>>>> So I'm hoping this has improved since Dave's measurements. How much has<br />
>> it improved? What's the current maximum packet latency under full<br />
>> load, Ive heard anecdotally that a friend of a friend gets 84 msec. *ping<br />
>> times under full load*, but he wasn't using flent or some other measurement<br />
>> tool of good quality that gives a true number.<br />
>>>><br />
>>>> 84 msec is not great - it's marginal for Zoom quality experience (you<br />
>> want latencies significantly less than 100 msec. as a rule of thumb for<br />
>> teleconferencing quality). But it is better than Dave's measurements showed.<br />
>>>><br />
>>>> Now Musk bragged that his network was "low latency" unlike other high<br />
>> speed services, which means low end-to-end latency. That got him<br />
>> permission from the FCC to operate Starlink at all. His number was, I<br />
>> think, < 5 msec. 84 is a lot more than 5. (I didn't believe 5, because he<br />
>> probably meant just the time from the ground station to the terminal<br />
>> through the satellite. But I regularly get 17 msec. between California and<br />
>> Massachusetts over the public Internet)<br />
>>>><br />
>>>> So 84 might be the current status. That would mean that someone at<br />
>> Srarlink might be paying some attention, but it is a long way from what<br />
>> Musk implied.<br />
>>>><br />
>>>><br />
>>>> PS: I forget the number of the RFC, but the number of packets queued on<br />
>> an egress link should be chosen by taking the hardware bottleneck<br />
>> throughput of any path, combined with an end-to-end Internet underlying<br />
>> delay of about 10 msec. to account for hops between source and destination.<br />
>> Lets say Starlink allocates 50 Mb/sec to each customer, packets are limited<br />
>> to 10,000 bits (1500 * 8), so the outbound queues should be limited to<br />
>> about 0.01 * 50,000,000 / 10,000, which comes out to about 250 packets from<br />
>> each terminal of buffering, total, in the path from terminal to public<br />
>> Internet, assuming the connection to the public Internet is not a problem.<br />
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>>><br />
>> <a href="https://secure-web.cisco.com/1sNc_-1HhGCW7xdirt_lAoAy5Nn5T6UA85Scjn5BR7QHXtumhrf6RKn78SuRJG7DUKI3duggU9g6hJKW-Ze07HTczYqB9mBpIeALqk5drQ7nMvM8K7JbWfUbPR7JSNrI75UjiNXQk0wslBfoOTvkMlRj5eMOZhps7DMGBRQTVAeTd5vwXoQtDgS6zLCcJkrcO2S9MRSCC4f1I17SzgQJIwqo3LEwuN6lD-pkX0MFLqGr2zzsHw5eapd-VBlHu5reC4-OEn2zHkb7HNzS1pcueF6tsUE1vFRsWs2SIOwU5MvbKe3J3Q6NRQ40cHI1AGd-i/https://lists.bufferbloat.net/listinfo/starlink" rel="noreferrer" target="_blank">https://secure-web.cisco.com/1sNc_-1HhGCW7xdirt_lAoAy5Nn5T6UA85Scjn5BR7QHXtumhrf6RKn78SuRJG7DUKI3duggU9g6hJKW-Ze07HTczYqB9mBpIeALqk5drQ7nMvM8K7JbWfUbPR7JSNrI75UjiNXQk0wslBfoOTvkMlRj5eMOZhps7DMGBRQTVAeTd5vwXoQtDgS6zLCcJkrcO2S9MRSCC4f1I17SzgQJIwqo3LEwuN6lD-pkX0MFLqGr2zzsHw5eapd-VBlHu5reC4-OEn2zHkb7HNzS1pcueF6tsUE1vFRsWs2SIOwU5MvbKe3J3Q6NRQ40cHI1AGd-i/https://lists.bufferbloat.net/listinfo/starlink</a><br />
>>><br />
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>><br />
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