Re: Starlink routing

["Forrest Christian (List Account)" <lists () packetflux com>]

Like I said,  they're calling it revolutionary.   Didn't say it was.

However the idea that you can build spaceships which are fully reusable was
certainly around the industry,  but the consensus was largely "we tried, it
costs too much,  so we're sticking with one use rockets".   Elon for
whatever reason is insane enough to dump a lot of cash in industries which
everyone said was a dead end and then has been lucky enough to prove the
old guard wrong.

Same for pretty much everything musk does,  including starlink.   So if
there is anything at all "revolutionary" here it's the insistence on
ignoring conventional wisdom.   I think it might be borderline insanity,
but it seems to work for him.

On Mon, Jan 23, 2023, 3:46 AM Jorge Amodio <jmamodio () gmail com> wrote:

> Musk didn't do anything revolutionary, besides launching a shload of LEO
> satellites.
>
> 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.
>
> DoD/NRO have been working on this for some time now, but any information
> is in the top secret blackhole.
>
> -J
>
>
> -Jorge
>
> On Jan 23, 2023, at 1:54 AM, Forrest Christian (List Account) <
> lists () packetflux com> wrote:
>
> 
> I think the thing they're calling revolutionary is the idea of those links
> being directional lasers.
>
> 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.
>
> 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.
>
> 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.
>
>
>
> On Sun, Jan 22, 2023, 8:55 PM Tom Beecher <beecher () beecher cc> wrote:
>
> > Yes re: Iridium. Contrary to what the Chief Huckster may say, inter-sat
> > comms are not some revolutionary thing that he invented.
> >
> > 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.
> >
> >
> > On Sun, Jan 22, 2023 at 18:25 Crist Clark <cjc+nanog () pumpky net> wrote:
> >
> > > I suspect, although I have no references, that satellite to ground
> > > connectivity is probably more “circuit-based” than per-packet or frame.
> > >
> > > 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.
> > >
> > >
> > > On Sun, Jan 22, 2023 at 3:06 PM Matthew Petach <mpetach () netflight com>
> > > wrote:
> > >
> > > > On Sun, Jan 22, 2023 at 2:45 PM Michael Thomas <mike () mtcc com> wrote:
> > > >
> > > > > I read in the Economist that the gen of starlink satellites will have
> > > > > the ability to route messages between each satellite. Would
> > > > > conventional
> > > > > routing protocols be up to such a challenge? Or would it have to be
> > > > > custom made for that problem? And since a lot of companies and
> > > > > countries
> > > > > are getting on that action, it seems like fertile ground for (bad)
> > > > > wheel
> > > > > reinvention?
> > > > >
> > > > > Mike
> > > >
> > > > Unlike most terrestrial links, the distances between satellites are not
> > > > fixed,
> > > > and thus the latency between nodes is variable, making the concept of
> > > > "Shortest Path First" calculation a much more dynamic and challenging
> > > > one to keep current, as the latency along a path may be constantly
> > > > changing
> > > > as the satellite nodes move relative to each other, without any link
> > > > state actually
> > > > changing to trigger a new SPF calculation.
> > > >
> > > > I suspect a form of OLSR might be more advantageous in a dynamic
> > > > partial
> > > > mesh between satellites, but I haven't given it as much deep thought as
> > > > would
> > > > be necessary to form an informed opinion.
> > > >
> > > > So, yes--it's likely the routing protocol used will not be entirely
> > > > "off-the-shelf"
> > > > but will instead incorporate continuous latency information in the
> > > > LSDB,
> > > > and path selection will be time-bound based on the rate of increase in
> > > > latency
> > > > along currently-selected edges in the graph.
> > > >
> > > > An interesting problem to dive into, certainly.   :)
> > > >
> > > > Thanks!
> > > >
> > > > Matt