The InterPlanetary Internet (IPN) project tries to make the Internet work on interplanetary connections. This is the current obsession of Vint Cerf, one of the people who really invented the Internet. It's a magnificent obsession, and it might even work.

You may think that current Internet technology (i.e the IP protocol and the layers above) could be used on radio communications since they have been used for several decades to communicate between spacecrafts and the Earth. But this solution suffers from major drawbacks:

  • delay. Internet protocols are based on repeated requests and answers at several layers. On Earth, the delay is usually one fraction of a second. Between two planets, it will take minutes or hours. Interactive protocols cannot be used, and bandwidth will be rare.
  • power supply. Photovoltaic energy is very low beyond Mars. And hydroelectric power stations are not an option in deep space.
  • maintenance. You may complain about your PC manufacturer support, but imagine your Web server sits somewhere between Jupiter and Saturn? You don't want to wait for the next mission in five years.
  • moving targets. Planets move and satellites move around the planets, so your server may be invisible from time to time.

The IPN team makes the following propositions:

  • delay: use gateways. Instead of communicating directly from your computer to a server on Saturn, you will interact with a gateway on Earth, which will interact with another gateway on Mars, and so on until the request gets to the server. Then the answer will follow the reverse path. Because TCP uses too many negociations between the client and the server, it will be replaced by a new "bundle protocol". The new protocol will not be faster than light, but it will ensure some reliability. Furthermore, you will have to pay for bandwidth; interplanetary Internet may never be free as in free beer.
  • power supply: power will be saved by using less verbose protocols and planning the communications.
  • maintenance: gateways will be duplicated so that redundancy ensures long-term operations. If necessary, aliens will be hired to go and fix the servers.
  • moving targets: relay satellites will be positioned at LaGrange points, which are special orbital locations where they will always remain visible.

Ok, but do we really need an interplanetary Internet? Is there any decent Web site on Uranus? Some people may need IPN for other reasons:

  • to facilitate the communication between the Nasa satellites and the Earth. The communication hardware could be much lighter, so that more space could be devoted to scientific hardware.
  • to call Web servers on other planets. It may be only for fun, but imagine a webcam on the Moon, directed at the Earth...

So is it working now? Can I ping Mars? Not yet. But it may start working after 2005, when the Nasa will or should deploy the first satellite network around Mars.

That's very exciting, but I have not won the Nobel prize yet, so I suppose I cannot be involved? On the contrary, the IPN team may offer projects to you if you are a post-graduate.

But first read the IETF draft at If it's a little too technical for you, try