Re: Starlink routing
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 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 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 >> wrote: >> >>> >>> >>> On Sun, Jan 22, 2023 at 2:45 PM Michael Thomas 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 >>> >>> >>
Re: Starlink routing
Solved years ago … https://ieeexplore.ieee.org/ielaam/92/8502886/8412572-aam.pdf -Jorge > On Jan 23, 2023, at 1:30 AM, Raymond Burkholder wrote: > > > >> On 1/22/23 21:54, Tom Beecher 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. > > I know of a group of satellite FPGA/RF guys who have worked on this doppler > thingy. It is a solved problem.
Re: Starlink routing
On 1/22/23 21:54, Tom Beecher 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. I know of a group of satellite FPGA/RF guys who have worked on this doppler thingy. It is a solved problem.
Re: Starlink routing
On 23/01/2023 0:42, Michael Thomas 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 For further reading try: https://www.internetsociety.org/wp-content/uploads/2022/11/Perspectives-on-LEO-Satellites.pdf -Hank
Re: Starlink routing
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 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 > wrote: > >> >> >> On Sun, Jan 22, 2023 at 2:45 PM Michael Thomas 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 >> >> >
Re: Starlink routing
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 wrote: > > > On Sun, Jan 22, 2023 at 2:45 PM Michael Thomas 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 > >
Re: Starlink routing
On 1/22/23 16:05, Matthew Petach wrote: On Sun, Jan 22, 2023 at 2:45 PM Michael Thomas 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? 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. Satellites move constantly relative to each other and to ground stations. There is a database available which contains the parameters for calculating a satellite's location at any instant in time. To maintain minimal link disruption, the idea is to calculate these relative relationships, and using some graph and network flow algorithms, you pre-calculate the links and then insert/remove those links and routes into the routing information base at the appropriate times. Then based upon latency, signal quality, and link availability, routing information is inserted/deleted into the forwarding information base. There are other contributors such as link saturation and overall end-to-end delays which could be applied based upon ground station state management. It becomes a multi-parameter link selection algorithm in a dynamic environment. Pretty much an interesting 'sdn' like scenario.
Re: Starlink routing
On 1/22/23 3:05 PM, Matthew Petach wrote: On Sun, Jan 22, 2023 at 2:45 PM Michael Thomas 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. One thing that is in their favor is that while they are moving, they are moving in a predictable manner. It seems that each router could, essentially, locally update routes until they are told otherwise? 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. Has IETF looked at this, do you know? Even if the routers can't interoperate with other systems, it would be good to have some routing clue with a lot of eyeballs on it to not make rookie mistakes. Mike
Re: Starlink routing
On Sun, Jan 22, 2023 at 2:45 PM Michael Thomas 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
Starlink routing
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
