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<p>It doesn't really solve the fundamental problem, though: Every
single copy of your cat video takes up RF bandwidth from the
satellite to the ground.</p>
<p>Sure, you can save on uplink bandwidth to the satellite by
putting a CDN server into space, but that's only a factor of two,
when terrestrial CDNs already get way more than that on long
distance fibre.</p>
<p>Let's do a back-of-the-envelope:</p>
<p>Base scenario: Population in Sampletown: 100,000. Cat video: 100
MB. Percentage of users wanting to watch cat video of Sampletown's
kindy's resident cat making off with a lego piece: 0.1% = 100.
40,000 Starlink satellites (looking ahead here). Number of people
interested in the video outside Sampletown: basically zero.<br>
</p>
<p>Variant 0: No CDN server in Sampletown, backhaul to Sampletown
via fibre, local users on fibre. <br>
</p>
<ul>
<li>Video sent to CDN server once: 100 MB = 80 Gb load on fibre.</li>
<li>Total spectrum use: zero<br>
</li>
</ul>
<p>Variant 1: CDN server in Sampletown, backhaul to Sampletown via
fibre, local users on fibre. <br>
</p>
<ul>
<li>Video sent to CDN server once: 100 MB = 800 Mb load on fibre.</li>
<li>Total spectrum use: zero</li>
</ul>
<p>Variant 2: Everyone in Sampletown uses Starlink, no CDN in space.</p>
<ul>
<li>Video uplinked 100 times: 80 Gb load on Starlink uplink
bandwidth.</li>
<li>Video downlinked 100 times: 80 Gb load on Starlink downlink
bandwidth.</li>
<li>Total spectrum use: 160 Gb<br>
</li>
</ul>
<p>Variant 3: Everyone in Sampletown uses Starlink, some sort of CDN
in space on the Starlink satellites themselves.</p>
<ul>
<li>Video uplinked only to satellites that don't have a copy.
After the first view of the video, the probability of the second
viewer using the same satellite that handled the first view is 1
in 40,000. l.e., almost none of the 100 views will strike a
satellite that already has a copy. That will only happen for
videos with tens of thousands of views. So you get : 80 Gb load
on Starlink uplink bandwidth.</li>
<li>Video downlinked 100 times: 80 Gb load on Starlink downlink
bandwidth.</li>
<li>Total spectrum use: 160 Gb</li>
</ul>
<p>Variant 4: Everyone in Sampletown uses Starlink, some CDN in
space residing on GEO sats, so there's one GEO sat where all cat
videos for Sampletown end up.</p>
<ul>
<li>Video uplinked to a Starlink sat on first request from CDN on
GEO sat: 800 Mb. Further uplink to GEO via laser - 800 Mb load
on laser.</li>
<li>Video downlinked 100 times: 80 Gb load on Starlink downlink
bandwidth, plus 80 Gb load on laser from GEO sat CDN to Starlink
satellite below.</li>
<li>Total spectrum use: 80.8 Gb, plus a bit of light pollution.
That's your factor of 2 improvement.<br>
</li>
</ul>
<p>Variant 5: CDN server in Sampletown, backhaul to Sampletown via
Starlink, local users on fibre.</p>
<ul>
<li>Video sent to CDN server once: 100 MB = 800 Mb load on
Starlink uplink and downlink to CDN.</li>
<li>Total spectrum use: 1.6 Gb. That's a factor of 50-100 over the
previous three scenarios.<br>
</li>
<li>But: That's not direct to site. It requires you as an end user
not to be on Starlink.</li>
</ul>
<p>It's the downlink to your dishy that spoils the party.<br>
</p>
<p></p>
<div class="moz-cite-prefix">On 17/04/2023 1:01 am, <a class="moz-txt-link-abbreviated" href="mailto:tom@evslin.com">tom@evslin.com</a>
wrote:<br>
</div>
<blockquote type="cite" cite="mid:1c03701d97063$85436500$8fca2f00$@evslin.com">
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<p class="MsoNormal">The cdns, at least for streaming, could be
higher since response time from them is not critical and the
LEOs could serve as relays to earth. Depends whether it’s
cheaper to do ISL between the LEOs and the higher satellites
than linking down to earth for the stream.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<div style="border:none;border-top:solid #E1E1E1
1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b>From:</b> Starlink
<a class="moz-txt-link-rfc2396E" href="mailto:starlink-bounces@lists.bufferbloat.net"><starlink-bounces@lists.bufferbloat.net></a> <b>On
Behalf Of </b>Ulrich Speidel via Starlink<br>
<b>Sent:</b> Sunday, April 16, 2023 3:04 AM<br>
<b>To:</b> <a class="moz-txt-link-abbreviated" href="mailto:starlink@lists.bufferbloat.net">starlink@lists.bufferbloat.net</a><br>
<b>Subject:</b> Re: [Starlink] fiber IXPs in space<o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p>Given that clients cache DNS responses (including iterative
responses from root servers), having DNS in space would be a
nice-to-have, but it's not the most pressing issue IMHO.<o:p></o:p></p>
<p>A far bigger problem is that a direct-to-site model like
Starlink's essentially rules out placing CDN servers in close
proximity to web clients. For those unfamiliar with them: CDNs
(content delivery networks, which now carry a huge percentage
of Internet content traffic) work by redirecting HTTP(S)
requests for content to a CDN server that's in closer
topological (and, by inference, physical) proximity to your
web browser. That keeps repeated requests for the same content
off expensive and scarce long-distance bandwidth while
allowing for fast TCP cwnd growth due to the low RTT in the
branch- and (thus collectively) bandwidth-rich local ISP
networks. But that doesn't work for Starlink: There's no way
to prevent everyone watching the same cat video via Starlink
in your area from having to take up scarce space segment
bandwidth each time the video is viewed. And we're talking
serious data volumes here, unlike for DNS.<o:p></o:p></p>
<p>You could, in principle, put CDN servers onto the satellites,
but that would require the many earthly CDN providers to (a)
persuade Elon that this is a good idea, (b) buy the service
off SpaceX as it's unlikely they'll be given rack space on the
Starlink fleet, and (c) you'd need a lot of storage capacity
on each satellite in space, with a much reduced probability of
a cache hit, since the fact that the satellites move across
pretty much the whole globe over time, your next cat video
download for your mates in town might need to come from a
different satellite, and the satellite you currently talk to
needs to cache not just stuff you and your neighbours like,
but also stuff everyone else around the globe likes. So make
that Chilean soap operas over Ukraine, Danish comedy for
Australia, Aussie Rules Footy for the US Midwest, and so on...
Or maybe quietly can the concept altogether. <o:p></o:p></p>
<div>
<p class="MsoNormal">On 16/04/2023 11:56 am, Rodney W. Grimes
via Starlink wrote:<o:p></o:p></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal">> On Fri, Apr 14, 2023 at 12:36?PM
David Lang <a href="mailto:david@lang.hm" moz-do-not-send="true"><david@lang.hm></a> wrote:<br>
> ><br>
> > On Fri, 14 Apr 2023, Rodney W. Grimes via Starlink
wrote:<br>
> ><br>
> > >> I keep wondering when or if Nasa will
find a way to move their DNS<br>
> > >> root server "up there" . DNS data is not
all that much... it is the<br>
> > >> original distributed database...<br>
> > ><br>
> > > As others have pointed out a "root server"
may not be very advantages,<br>
> > > but what I think would be far better is to
put up a couple of anycast<br>
> > > recursive caching resolvers, aka <a href="http://8.8.8.8/8.8.4.4" moz-do-not-send="true">8.8.8.8/8.8.4.4</a> and almost
anyone<br>
> > > can do that, including starlink itself.<br>
> ><br>
> > I believe that the root servers are all (or almost
all) anycast nowdays.<br>
> <br>
> Anycast is perfect for an orbital DNS.<br>
<br>
BUTT, root servers are NOT recursive or caching, they serve
a very<br>
small limitited set of data that changes at low frequency (I
am<br>
not sure of the current rate of updates, but it use to be
only<br>
once daily.)<br>
<br>
Anyone can bring up there own replicate of a root server
locally,<br>
I do, and have for 2 decades, its a rather trivial thing to
setup<br>
and maintain. But unlike a root, I also turn on recursision
and<br>
caching.<br>
<br>
Again IMHO, a caching recursive any cast server ala <a href="http://8.8.8.8" moz-do-not-send="true">8.8.8.8</a> would<br>
be far more useful than just a stock "root server."<br>
<br>
> -- <br>
> AMA March 31: <a href="https://www.broadband.io/c/broadband-grant-events/dave-taht" moz-do-not-send="true">https://www.broadband.io/c/broadband-grant-events/dave-taht</a><br>
> Dave T?ht CEO, TekLibre, LLC<br>
--<br>
Rod Grimes <a href="mailto:rgrimes@freebsd.org" moz-do-not-send="true" class="moz-txt-link-freetext">rgrimes@freebsd.org</a><br>
_______________________________________________<br>
Starlink mailing list<br>
<a href="mailto:Starlink@lists.bufferbloat.net" moz-do-not-send="true" class="moz-txt-link-freetext">Starlink@lists.bufferbloat.net</a><br>
<a href="https://lists.bufferbloat.net/listinfo/starlink" moz-do-not-send="true">https://lists.bufferbloat.net/listinfo/starlink</a><o:p></o:p></p>
</blockquote>
<pre>-- <o:p></o:p></pre>
<pre>****************************************************************<o:p></o:p></pre>
<pre>Dr. Ulrich Speidel<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre>School of Computer Science<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre>Room 303S.594 (City Campus)<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre>The University of Auckland<o:p></o:p></pre>
<pre><a href="mailto:u.speidel@auckland.ac.nz" moz-do-not-send="true" class="moz-txt-link-freetext">u.speidel@auckland.ac.nz</a> <o:p></o:p></pre>
<pre><a href="http://www.cs.auckland.ac.nz/~ulrich/" moz-do-not-send="true">http://www.cs.auckland.ac.nz/~ulrich/</a><o:p></o:p></pre>
<pre>****************************************************************<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre><o:p> </o:p></pre>
<pre><o:p> </o:p></pre>
</div>
</blockquote>
<pre class="moz-signature" cols="72">--
****************************************************************
Dr. Ulrich Speidel
School of Computer Science
Room 303S.594 (City Campus)
The University of Auckland
<a class="moz-txt-link-abbreviated" href="mailto:u.speidel@auckland.ac.nz">u.speidel@auckland.ac.nz</a>
<a class="moz-txt-link-freetext" href="http://www.cs.auckland.ac.nz/~ulrich/">http://www.cs.auckland.ac.nz/~ulrich/</a>
****************************************************************
</pre>
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