With these peer-to-peer networks, users start to support their own level of activity

Andrew Herbert, Microsoft

Peer-to-peer networks such as Gnutella and Freenet rely on their members to help keep the system running and to ensure there is enough data to swap.

Unfortunately, management systems for peer-to-peer networks struggled when they had tens or hundreds of thousands of users, said Andrew Herbert, a researcher at the Microsoft lab.

"We cannot rely on managers and people to run these systems; it's too difficult," said Mr Herbert. "We need to find a way for these systems to look after themselves in an automatic way."

Dr Herbert and his colleagues are working on software called Pastry, which helps peer-to-peer networks spontaneously form, but does not impose a huge management burden on participating machines.

Rolling Pastry

At the moment, most peer-to-peer networks are made up of people swapping music, programs, movies and images.

Napster is not a proper peer-to-peer network

But as the web becomes more about doing business, machines are expected to form peer-to-peer networks automatically.

To help bring this about, Pastry uses a peer-to-peer addressing scheme inspired by the way that rumours and gossip spread through human communities.

The members of a Pastry network only connect to a few nodes in the entire system.

Typically they link to machines that have addresses close to theirs, as well as at least one in the other numerical domains of the addressing scheme.

Home vision

Experiments have shown that Pastry can reliably send information to network members, even though they may regularly join and leave the system.

"With these peer-to-peer networks, users start to support their own level of activity," said Dr Herbert.

This topology also reduces the burden of passing information around because one node does not have to send its data to all the nodes requesting it.

The Pastry protocol could also be useful for managing the ad-hoc networks that wireless devices form, or in the home to let smart devices swap and share information.

"We are finding that people in their homes are using more and more computers and have to invest a lot of time in configuring and learning how to use them," said Dr Herbert. "Pastry helps non-technical people put networks together."