Having recently learned about the Interplanetary Internet in development by NASA's Jet Propulsion Laboratory, and inspired by Kim Stanley Robinson's novel 2312, I began to wonder about the actual reality of a dense information network spanning the whole Solar System.


  • What would a typical user use such a network for?
  • How reliably would it work?
  • What would the expected bandwidths be?
  • Would using it be exorbitantly expensive?
  • And how would it actually feel to use such a system?


First of all, the network infrastructure would be there. Relay clusters are in place in various orbits around the planets and the Sun, some even around dwarf planets or asteroids.

Second, the methods of transmission would be ones currently known to us: Laser and radio (and data mules, where necessary).

Third, there would be a significant diaspora of the human race all over the Solar System. Though travel is relatively cheap, it is not necessarily convenient.

EDIT (14.8.2016), bandwidth hints: NASA tested a Moon-Earth laser broadband in 2013 achieving a nice 622 Mbps with a puny, low-powered device. They are testing a more advanced setup in 2017: "The LCRD will be capable of shifting 1.25Gbps of encoded traffic, or 2.88Gbps of uncoded data using laser equipment that is just four inches long and which uses considerably less power than a radio communications system." Link to article. Exciting times!

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    $\begingroup$ More interesting than bandwidth, would be latency. A quick search shows transmitting a signal taks between 5 to 20 min. Requesting some Wikipedia article would take at least double the time (without cached values) So a quick look at a link would take forever. This could push IaaS provider that will automatically replicate your Content on different planets in order to allow everyone in the solar system to access your service in an acceptable manner. $\endgroup$ Commented Aug 13, 2016 at 10:01
  • $\begingroup$ Encryption would be important, because there is no way to physically protect a connection between two celestial bodies. However, current protocols require multiple round trips to establish an encrypted connection, which is prohibitive due to the latency times. Different protocols would be needed. $\endgroup$
    – Philipp
    Commented Aug 13, 2016 at 10:28
  • $\begingroup$ Yes, those are interesting points. They are also mentioned in the Wikipedia article about Interplanetary internet. I am more interested in the actual role of the interplanetary internet as a medium of information exchange, and how this relates to the actual usage profiles and user experiences. Could you elaborate on that? $\endgroup$
    – vodrilus
    Commented Aug 13, 2016 at 11:24
  • $\begingroup$ Hi vodrilus. It's entirely your choice whether, when or which answer to accept, but since you are new here, I want to point out that it's usually a good idea to wait at least a day or two before accepting an answer. Answers on Worldbuilding tend to be rather long and in-depth, and can take some time to write; additionally, different people are active on the site during different times of the day. Waiting at least a day before accepting an answer improves the chances of getting answers that address the question from different perspectives or are more in-depth. $\endgroup$
    – user
    Commented Aug 13, 2016 at 18:31
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    $\begingroup$ Related: worldbuilding.stackexchange.com/q/10601/28 $\endgroup$ Commented Aug 14, 2016 at 5:08

3 Answers 3


Actually, there is a network with properties similar to those that would likely be seen on an interplanetary version of the Internet. We can use it for comparison.

It's called FidoNet.

FidoNet uses a store-and-forward architecture to cope with high cost of long distance transfers, and batch processing of messages and requests. It has a highly hierarichal address structure where the node addresses encode information about each node's location. Communication between nodes has historically been over dial-up modem links, but Internet links have also been used.

The three main services provided by FidoNet are netmail, echomail and file requests (freqs).

Netmail is mainly one-to-one communication, similar in principle to Internet e-mail. It is what all other services provided over FidoNet are built on top of, similar in a way to how everything on the Internet is built on top of IP.

Echomail is one-to-many communication, similar in principle to Usenet or later-date web forums or question and answers sites.

Freqs is usually person-to-system communication, with the purpose of obtaining files made available by a remote system. It was often, but not exclusively, used for software distribution, where each system didn't have to have everything locally available. At a time when significant storage capacity came at a hefty cost, this helped reduce the up-front cost of setting up a node but transferred that cost to an on-going cost of transferring files requested by the users. Because of these ongoing costs, excessive freq'ing was commonly seen as disrespectful.

Because FidoNet used store-and-forward techniques and often multiple hops, delivery times of hours or days were not uncommon. Because dial-up links were the norm during FidoNet's days of glory, instead of tying up the phone line (and preventing others from reaching the node you were on), reading and writing messages offline then connecting to make a batch transfer of anything new was common. There were several specialized software packages that provided nice, relatively user-friendly user interfaces for managing netmail, echomail and freqs. Systems often exchanged messages during the night, as not only was expected usage often lower, cost was often lower as well.

FidoNet also allowed for "crashmail", which was generally reserved for high-priority traffic. Crashmail was identical to netmail, but requested any system it passed through to pass the traffic on as quickly as possible. Unwarranted use of crashmail was seen as exceedingly rude, because it incurred an additional cost to every system administrator along the message delivery path, but it did have legitimate uses. Some systems disallowed crashmail, treating it as regular netmail.

See how this might be similar to how an interplanetary Internet might realistically function?

  • Links are intermittent. Deploying sufficient nodes to always guarantee a direct path from one endpoint to another will likely be prohibitively expensive, and nodes are bound to go offline every now and then for any of a phletora of reasons, and nodes will sometimes be busy handling (possibly higher-priority) traffic to or from a different node. Designing around a store-and-forward architecture reduces the impact to the end user of such intermittency; the end user will simply see that the message took slightly longer to be delivered, and if they look at trace data (similar to e-mail's Received: headers) they may see that the data took an unexpected path toward its destination or even was re-routed while in transit.
  • Speed of light propagation delay is considerable. On Earth, even a one-second propagation delay is a long time; for an interplanetary Internet, it takes one second just to get from Earth to Earth's moon, let alone send an acknowledgement back. Any form of interactive use will be prohibitively slow, so batch, likely message-based, processing makes sense.

Combine these two, and we get a network based around the idea of taking some kind of "message" or "package", accepting responsibility for its delivery, and arranging for its eventual delivery to a base station near the recipient (where "near" might mean "on the same planet"), from where it would be routed in a manner more suitable for planet-local traffic. While interplanetary, the traffic could then be routed by a variety of methods or links, depending on its priority and what links are currently online and available. Correspondingly, users may be charged different rates for different-priority traffic, and some ultra-high priority classes may be restricted to certain users of the network or even the network itself. Correspondingly, the lowest-priority traffic might simply piggyback on a transport spacecraft, with all of what that means in terms of delivery times.

Under the hood, strong cryptography and advanced compression and error-correcting algorithms will very likely be used to detect and correct for data corruption, reduce the amount of data that needs to be transmitted, ensure data privacy against eavesdroppers, and ensure that the correct user is appropriately billed for their own traffic and not anybody else's, among other possible uses. Remember that at anything resembling interplanetary distances, bandwidth is at a large premium (the terrestrial connection to my home could pretty much saturate that about a gigabit per second you mentioned NASA toying with for the LCRD for next year, if I simply spoke to my ISP and paid for more upstream bandwidth), and retransmissions are very expensive for the network, so there are incentives to reduce both as much as possible. All this will be transparent to the user of the network, who will simply see the end result of their messages being delivered and billed for.

Thus we can answer your questions.

What would a typical user use such a network for?

Batch- or message-oriented communications. It takes too long to deliver anything for any real-time use, so once you leave your own planet's planetary network (which might possibly include the moons and spacecraft in orbit of that planet), you give up getting an immediate response.

Thus, for interplanetary traffic, the user experience will be more like sending paper mail, or posting on a web forum, or sending an e-mail, and waiting to get a reply, than the back-and-forth of instant messaging or video chat. If adequate bandwidth is available, it's certainly possible to send images, audio or video back and forth, but directly interacting with the person or system at the other end of the link will generally not be practical simply due to the inherent latency of the physical distances involved, let alone those potentially introduced by there existing no complete, direct path between the two endpoints at the time.

How reliably would it work?

A store-and-forward network can be very reliable (almost arbitrarily reliable), especially if the individual nodes and link hops are sufficiently reliable and the hops are short enough that immediate confirmation from the next node is reasonable. Because any node will retain the message at the very least until it receives confirmation from the next node along the way that the message has been successfully received and passed all relevant checks, a message can always be retransmitted, possibly through a different node or path, should the need arise. Borrowing from one approach of mitigating the Two Generals' Problem, high-priority traffic can be sent through multiple paths simultaneously, to improve the chances of one of the copies making it through quickly in case a node along the way becomes unavailable while the message is en route. The nodes would likely be made sufficiently autonomous that they are able to determine themselves the most appropriate "next" (closer to the ultimate destination) node to send the data to, which would allow the network to gracefully handle nodes becoming unavailable while data is in transit.

What would the expected bandwidths be?

Impossible to say. Ultimately, the limiting factor will probably be the Shannon-Hartley theorem, which gives the maximum theoretical information rate of a communications channel of a given bandwidth and a given signal-to-noise ratio. We can improve the S/N ratio by increasing power to the transmitter, but that costs energy. This is one of the places where different classes of traffic may be employed; a high-priority message may warrant using some reserve battery capacity to increase the transmitter output power, to help ensure its successful delivery, at the cost of reduced ability to do that again in the immediate future (until the batteries have been recharged from whatever primary electricity source, such as solar panels or RTGs, that the node uses).

Would using it be exorbitantly expensive?

Not necessarily, but that depends very much on your definition of "exorbitantly". As I have already said, different traffic priorities could be charged at different rates, and the user would select the traffic priority level appropriate for the message they are sending or the request they are making. The vast majority of traffic would likely use a "bulk" classification of some kind, which basically means best-effort and transmission whenever the network would otherwise be idle, with no real delivery time guarantees. Higher priority classes would be used for any traffic that requires some form of expediated delivery, kind of like how you can choose between priority mail and economy mail when sending a postal package to someone.

The major cost for something like this will be up-front, in deploying the large number of nodes that will be required to provide reasonable latencies. That cost will need to be recouped somehow, and it's likely that user fees and data transfer fees will be a major part of how the cost of establishing the network is recovered. Because in your world "travel is relatively cheap" but "not necessarily convenient", the cost of establishing the network might be lower than it would be in our world, and the ultimate cost to the end user for using the network should, in an ideal world, reflect that lower cost to the network operator. There will be ongoing costs for replacing nodes that become unusable for various reasons, but with some planning ahead, those costs can be spread out over time.

How would it actually feel to use such a system?

You would be considering everything rather carefully. Not only because even in the best of cases delivery can easily take hours (and there will likely be no guaranteed way to recall or change a message once you have sent it), but also because you lose much of the back-and-forth available with today's Earth-bound Internet where traffic roundtrip times are measured in fractions of a second.

Using an interplanetary network will probably feel more similar to e-mail, or FidoNet, or even mail order, than it will feel similar to casually browsing the web, looking at whatever you find that looks interesting. Planet-local storage and "package" preparation will be an absolute requirement to make the end-user experience reasonable.

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    $\begingroup$ See also: Usenet, newsgroups that (originally) used a store-and-forward protocol resulting in latency of hours to days. People did still have group conversations, but there was a fair bit of duplication. $\endgroup$ Commented Aug 14, 2016 at 5:06
  • $\begingroup$ There's a mention of similar protocols being currently used (or tested?) by Saami reindeer herders in Northern Sweden in this interview of Vint Cerf abou the Interplanetary Internet $\endgroup$
    – vodrilus
    Commented Aug 14, 2016 at 9:13

What would a typical user use such a network for?

Well we talking about interplanetary internet so the user will (want) to use it for what we use it today.

  • Communication
  • Information
  • Entertainment

How reliably would it work?

I would assume that the network would be very reliably (on the higher layer). The question would not be if the message arrives, but when. However interference could delay a message for hours (or days?).

What would the expected bandwidths be?

I think we can build a network that has enough bandwidth, but I didn't found information on this. So the rest of my answer assumes we have enough bandwidth.

Would using it be exorbitantly expensive?

I think the network would be quite expensive. However not necessary for the end user. A system wide internet could be subsidized by government and content provider which want to sell there content to the users. That's what happens today in not so dense populated regions to get fast internet there.

And how would it actually feel to use such a system?

If the user access planetary (his current location) resources there won't be a difference from today. As soon as he actually uses the interplanetary network, however somethings most likely will change drastic.


Any online game that has real-time interaction won't work. You could still have something like racing against ghosts of other players, simple leaderboards or playing something like chess. Like in the time when you played chess via mail (not E-Mail).

Instant Video wouldn't be so instant as long as it is not cached anywhere. Big players could maybe hold a copy of all there content in different datacenters around the system. However if you want to use a service that don't provide this, the question would not be "what should we watch (now)", but "what should we watch tomorrow". So you will request the content and watch it when it comes. If you have an abo for series they will start sending you a copy to watch offline as soon as it is released (maybe still DRM protected).


News will be as today. You will still be notified but it will take longer. This could result in a trend back to traditional media. If you need to wait several hours for your information maybe you can wait an hour longer for verified information.

Surfing the internet from link to link will not work. There could be an indicator how long it would take to load a Link. Is it a local resource or it is already cached. Often accessed sides will (as already today) be cached. But good caching will get much more important. Surfing will often result in I want to read this and that later. On the technical site requesting a Website would not only deliver the site but also other sites of the domain and other linked content directly.


We would not use messengers as much. There wont be any direct communication. We will go back to E-Mail, or something similar. Maybe we would write more and longer letters, like in the time where there was no telephone. Communication on websites should change to (in order to be still somehow use full).

Forums will need to structure the communication better. You need to know which post related to which other in order to follow the discussion. Some websites will only used locally because the discussions are to fast to allow anyone from far away to participate. Other Sites could use some mechanism to counter this by showing posts only after a specific time they where posted (when the user pressed send, not the server received the post).

I would assume a raising popularity of IaaS provider that will replicate your content over the howl system. Even small blogs that currently are hosted in private environments maybe want to migrate to bigger providers. We would maybe also see more toplevel domains that indicate the location, like .us.earth or .mars, .pluto and .sun.

The underling protocols of the internet must change drastic as the application the end user uses must change in order to give him enough information what will happens if he clicks this link. Nobody wants to click a link in twitter and sitting there for hours until the site loads.

I think log distance communication will feel more like in old days before telephone. There wont be any non local news with live broadcast from the place where something happens. Nobody can ask questions to the journalists at the place. Most likely the information will still be published as soon as it is available. But the livetcker would not be live anymore.

  • $\begingroup$ This covers almost all the bases, so I'm accepting this one. The IP protocol (redundant language... ugh) can't handle interplanetary lag due to shifting IP addresses, so domain names would have to be resolved differently. The effects of cached internet are very interesting. We'll have to make do with old cat videos from time to time. (The language could use some work, too, but I guess you're not a native, either.) $\endgroup$
    – vodrilus
    Commented Aug 13, 2016 at 15:27
  • $\begingroup$ why would the ip addresses shift around? no reason they should. it is the layer above that that needs reworking. $\endgroup$
    – lijat
    Commented Aug 13, 2016 at 17:00
  • $\begingroup$ Oh, I must have been out of it. I somehow thought about DNS look-up, which is actually a part of the application layer. That's what Cerf says doesn't work in this (long-ish) interview, anyway: link $\endgroup$
    – vodrilus
    Commented Aug 14, 2016 at 8:48

It seems inevitable that the network and its content would be divided up, as viewed from any given place, by bandwidth and latency. For example, assume you're on Mars. MarsNet is accessible with the kind of latency we experience on Earth at present. Phobos and Deimos are close enough to be part of MarsNet.

But I want something that isn't on MarsNet. Where do I look next? EarthWeb is plausible, but Earth is between 3 and 25 light-minutes distant in each direction (allowing for a bit of relaying around the Sun for high-bandwidth connections) and nobody wants to wait that long for an interactive search request.

So there will be a cache of EarthWeb on Mars, and of MarsNet on Earth, and those will be updating continuously. Search engines' indexes should get high priority for updates, so that you can find out something exists fairly easily, even if you have to wait for it to arrive, which is more acceptable.

And Mars' copy of EarthWeb will be being sent on to asteroid settlements that are nearer to it than to Earth, and to the moons and trojans of Jupiter, when it's a shorter hop, and so on. The usual way of doing a search will be "Local web plus local caches" and the details of the addressing and caching will take some work, but chunks of them are already solved by archive.org.

  • $\begingroup$ Nice answer. I didn't realize that part of the caching process is actually already partly solved. This is still a bit narrow, considering the wide range of uses for the current (terrestrial) Internet. I might disagree about Phobos and Deimos being close enough to form a sufficiently homogenous transmission environment for a planetary protocol (but I'm not an expert). Might be more efficient to have a dedicated MarsNet protocol and an intermediate protocol between it and Phobos/DeimosNet. $\endgroup$
    – vodrilus
    Commented Aug 13, 2016 at 15:19
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    $\begingroup$ The distance between Mars and its moons is much less than the distance between the Earth and its moon (our moon is somewhat more than one light second away). Since the majority of what people look for is local, most people on Marsnet are not going to be too worried about what is for sale on Kajiji on Earth. Research and downloads of movies and so on will be a bit like a magazine subscription, you will get an update when the Earth cache is updated with the latest content. $\endgroup$
    – Thucydides
    Commented Aug 13, 2016 at 23:32

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