<div dir="ltr"><div dir="auto"><div><br></div>Musk didn't do anything revolutionary, besides launching a shload of LEO satellites.</div><div dir="auto"><br></div><div dir="auto">NASA and DoD have been working for long time on optical space communications, last year LCRD was launched and preliminary tests using it as a relay showed 622Mpbs, this year NASA will include on one of the cargo missions to ISS ILLUMA-T that will be installed at ISS and it is expected to provide 1.24Gpbs or more using LCRD as a relay with the two ground stations, one in HI, and one in CA.</div><div dir="auto"><br></div><div dir="auto">DoD/NRO have been working on this for some time now, but any information is in the top secret blackhole.</div><div dir="auto"><br></div><div dir="auto">-J</div><div dir="auto"><br><br><div id="m_-9016984634096727802AppleMailSignature" dir="ltr">-Jorge</div><div dir="ltr"><br><blockquote type="cite">On Jan 23, 2023, at 1:54 AM, Forrest Christian (List Account) <<a href="mailto:lists@packetflux.com" target="_blank">lists@packetflux.com</a>> wrote:<br><br></blockquote></div><blockquote type="cite"><div dir="ltr"><div dir="auto"><div>I think the thing they're calling revolutionary is the idea of those links being directional lasers.</div><div dir="auto"><br></div><div dir="auto">It makes some sense... if you can basically emit the same signal you'd shoot down a strand of single mode but aim it through the mostly vacuum of space in the exact direction of your neighbor then you've got something... Essentially the equivalent of a fiber optic network in space. </div><div dir="auto"><br></div><div dir="auto">For fun I tried plugging in some frequencies of light into a doppler calculator. Unfortunately that's where my "would the relative speed that mere mortals could attain make enough of a difference to affect a typical optical receiver" investigation ended as I'm mobile right now and can't do the rest of the work very easily. I'd be curious if the relative speed would be enough to cause enough shift to move it out of the pass band if a typical dwdm channel.</div><div dir="auto"><br></div><div dir="auto">And, I agree that little of what musk takes credit for is revolutionary. But what I do think he deserves credit for is being insane enough to try things everyone says is unworkable and failed in the past and somehow making at least some of them work. Having more money than God helps too. </div><div dir="auto"><br></div><div dir="auto"><br><br><div class="gmail_quote" dir="auto"><div dir="ltr" class="gmail_attr">On Sun, Jan 22, 2023, 8:55 PM Tom Beecher <<a href="mailto:beecher@beecher.cc" rel="noreferrer noreferrer noreferrer" target="_blank">beecher@beecher.cc</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div><div><div dir="auto">Yes re: Iridium. Contrary to what the Chief Huckster may say, inter-sat comms are not some revolutionary thing that he invented. </div><div dir="auto"><br></div><div dir="auto">It’s also not likely to function anything like they show in marketing promos, with data magically zipping around the constellation between nodes in different inclinations. Unless they have managed to solve for the Doppler effect in a way nobody has thought of yet. </div><div dir="auto"> <br></div><div dir="auto"><br></div></div></div></div><div><div><div><div><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sun, Jan 22, 2023 at 18:25 Crist Clark <<a href="mailto:cjc%2Bnanog@pumpky.net" rel="noreferrer noreferrer noreferrer noreferrer" target="_blank">cjc+nanog@pumpky.net</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(204,204,204)"><div dir="auto">I suspect, although I have no references, that satellite to ground connectivity is probably more “circuit-based” than per-packet or frame.</div><div dir="auto"><br></div><div dir="auto">Iridium has done inter satellite communication for decades. I wonder if it wouldn’t be something very similar. Although it would be totally on-brand for them to do it some “revolutionary” new way whether it actually makes any sense or not.</div><div dir="auto"><br></div><div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sun, Jan 22, 2023 at 3:06 PM Matthew Petach <<a href="mailto:mpetach@netflight.com" rel="noreferrer noreferrer noreferrer noreferrer" target="_blank">mpetach@netflight.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(204,204,204)"><div dir="ltr"><div dir="ltr"><br></div><br><div class="gmail_quote"></div></div><div dir="ltr"><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sun, Jan 22, 2023 at 2:45 PM Michael Thomas <<a href="mailto:mike@mtcc.com" rel="noreferrer noreferrer noreferrer noreferrer" target="_blank">mike@mtcc.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(204,204,204)">I read in the Economist that the gen of starlink satellites will have <br>
the ability to route messages between each satellite. Would conventional <br>
routing protocols be up to such a challenge? Or would it have to be <br>
custom made for that problem? And since a lot of companies and countries <br>
are getting on that action, it seems like fertile ground for (bad) wheel <br>
reinvention?<br>
<br>
Mike<br>
<br></blockquote><div><br></div><div><br></div></div></div><div dir="ltr"><div class="gmail_quote"><div>Unlike most terrestrial links, the distances between satellites are not fixed, </div><div>and thus the latency between nodes is variable, making the concept of <br>"Shortest Path First" calculation a much more dynamic and challenging </div><div>one to keep current, as the latency along a path may be constantly changing </div><div>as the satellite nodes move relative to each other, without any link state actually</div><div>changing to trigger a new SPF calculation.</div><div><br></div><div>I suspect a form of OLSR might be more advantageous in a dynamic partial </div><div>mesh between satellites, but I haven't given it as much deep thought as would </div><div>be necessary to form an informed opinion.</div><div><br></div><div>So, yes--it's likely the routing protocol used will not be entirely "off-the-shelf" </div><div>but will instead incorporate continuous latency information in the LSDB, </div><div>and path selection will be time-bound based on the rate of increase in latency </div><div>along currently-selected edges in the graph.</div><div><br></div><div>An interesting problem to dive into, certainly. :)</div><div><br></div><div>Thanks!</div><div><br></div><div>Matt</div><div> </div></div></div>
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