The NASA space agency has begun work on creating an 'Interplanetary Internet' linking the earth to the rest of the solar system, according to the co-inventor of the IP Internet protocol, Vint Cerf.

Speaking at the Internet Society conference, Inet 98, in Geneva this week, Cerf - coinventor of TCP/IP and senior vice president of MCI - unveiled the plan for Internets on other planets. He said: "It is time to think about Internets that are out of this world."

Scientists from NASA and the US Jet Propulsion Laboratory are developing orbiting interplanetary Internet gateways, according to Cerf, integrating technology already being used for communications by the current Mars mission.

Cerf said: "If you think that this is fantasy then let me assure you that this is real. It took 30 years to get the Internet where it is so you have to look ahead 30 years and think what you will need."

Because IP was designed to work in very low delay environments it cannot be used in space, where the delay can be hours rather than seconds. To be transmitted across space the IP traffic will be repackaged using interplanetary transmission protocols, already used to communicate with the Mars Rover, which are not affected by delays.

The aim is cut the costs of communication by using non proprietary equipment where possible.

The orbiting gateways will translate the IP traffic into the interplanetary transmission protocol as it leaves the earth, and then retranslate it to be beamed down to Mars.

The plan, according to Cerf, is to create a fully functioning Internet on another planet. "We want to make it a flexible architecture so it doesn't matter where it ends up, it will work anywhere."

He said that the Interplanetary Internet will be used by researchers at first, but that the underlying design could be used to deliver the same sorts of applications that are found on the existing Net, including electronic commerce at some point in the future.

Cerf said the technology used to create the Interplanetary Internet could have an application on earth as networking speeds increase. "Some of the ideas for long delays in space may make sense on earth," he said.

He added that, in the next four to five years, the companies will be using circuits running millions of bits per second, and that achieving high transmission speeds on earth will cause similar problems to those created by transmission over long distances in space.

For instance, one limitation of IP is that it requires acknowledgement for messages sent, which causes problems when data is sent over long distances - such as into space - or at high speeds.

On earth, Cerf predicted a huge upsurge in demand for the Internet in the next decade, coming from companies that are currently building Intranets.

He believes that companies will realise that they can only get the full benefit from their corporate Intranets when they link up to the 'public' Internet.

Steve Ranger is a reporter on Computing.