The (Inter) PlanetaryInternet is not science fiction but a real attempt to define protocols and infrastructure to allow efficient communications between probes, landers and manned spacecraft between bodies in the solar system. With current technology, a lot of store and forward involved due to signals taking hours to propagate but more economical than setting up dedicated point to point networks for each mission. InternetProtocolVersionSix will allow lots of address space for this.

See http://www.ipnsig.org/
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Will there be planetary GlobalPositioningSystem''''''s as well? (MoonGps, MarsGps ...)

''Yes. Not all-encompassing satellites initially, but researchers are studying "pseudolites" - balloons hovering in place to serve a similar triangulation function for mars rovers; see http://arl.stanford.edu/~rover/scpa_3d.html.''
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Anyone who works with branch offices or customers in multiple timezones knows what it is like juggling time zones (waking up at 2am local time for conference calls). As population expands through the solar system, there will need to be a feature in everyone's HandHeld or whatever is being used then to pinpoint PlanetaryTimeZones. taking into account planet rotation (different for each one not fixed #hours ahead or behind as it is now), planetary "year" and signal delay. It will be highly dynamic. Such algorithms are probably already in use by JPL etc. To schedule a conference "session" between Earth, Titan and Mars for 2am (Earth)EST would need this software. This would just be a time window when questions and replies could be scheduled because of the time delay (unless someone invents SubSpace transmission by then, in which case it could be a call). For instance, the Spirit Mars Rover team sends one set of instructions a day and has to wait to see the result the next day; if they get it wrong, it works out to a $4M per day mistake for that day according to an interview with one of the team.

''What's the point of a conference call with long comm delays? You'll have to settle for an email conversation - or something similarly asynchronous - and the asynchronicity means you don't need to schedule a conference call - just send your message and they'll get it when they get it. Of course, it helps to know the timezones if you want to know when you're likely to receive a reply, and the routers need to know when they have a line of sight for sending the mail, but that's not the same as scheduling an absurdly slow conference call between people.''

''And forget about interplanetary network gaming - someone on a dialup on the other side of the world from the server is a LowPingBastard compared to someone orbiting a different planet. Although I'm sure PlayByEmail will be popular.''

It gets worse once you consider orbital locations and how inconsistent this will be. The distance to Mars ranges from 0.5 to 2.5 AUs depending on their orbital positions at the time. 1AU = 8 light-minutes. So depending on the time of year, you would have anywhere from a 4 to 20 minute delay... double that if you want feedback of confirmation. Not to mention the expense of that long a distance of communication. Finally, there's the problem of even longer delays when an intermediary would have to be used around a Mars-Sun-Earth eclipse... but that's a minor concern compared to others. Colonies on Titan would have it even worse with the 9.54AU radius of Saturn's orbit.