Creating a computer currency

Computer scientists are using the latest version of peer-to-peer video sharing software to explore a next-generation electronic commerce model that uses bandwidth as a global currency.

The software, called Tribler, is available for download beginning today (Aug. 29) on the School of Engineering and Applied Sciences (SEAS) Web site.

Once installed, the software lets those who download it join a peer-to-peer video sharing network. Tribler was originally created by scientists in The Netherlands, at Delft University of Technology and Vrije Universiteit in Amsterdam. The most recent release was created in collaboration with scientists at Harvard’s School of Engineering and Applied Sciences.

Peer-to-peer networks are different from centralized networks that allow users to access resources concentrated in a single place. Perhaps the best known peer-to-peer networks are those created to share music files. In those networks, a user can download songs from other members’ computers in exchange for allowing network members access to music on his or her own machine.

In contrast, a more centralized system, such as the iTunes music site created by Apple Inc., draws users to a central source —the iTunes store — to get their music.

Tribler allows users to create a peer-to-peer video sharing network, as opposed to the more centralized YouTube site, for example, where all the resources — the computer, hard drive storage space, and Internet connections — are paid for by Google Inc., which owns YouTube.

David Parkes, John L. Loeb Associate Professor of Natural Sciences at SEAS, worked on the new version of Tribler with Tribler technical director Johan Pouwelse, an assistant professor at Delft University of Technology who is visiting at SEAS. Parkes said that today’s peer-to-peer networks already contain the roots of a new system of commerce. The new version of Tribler, he said, takes those features a step further.

In today’s peer-to-peer networks, members do much more than just exchange files. Functioning below the surface, the peer-to-peer software uses the resources of a member’s machine to make the entire network function more smoothly. Parkes used the example of a peer-to-peer telephone system, which sends telephone calls over the Internet and which is used currently by millions around the world.

While a Bostonian may be talking with a network member in San Francisco, the software is using the Bostonian’s computer for more than just that phone call. It is also helping the rest of the network function more effectively. If a network member in Japan, for example, wants to talk to another member in France, the call would usually go through directly. If there are network blocks such as firewalls that interfere with that path, however, the next best path may be through the wires, routers, and other gear that lead from Japan to Boston and Boston to France. If that were the case, the network would use the Bostonian’s computer resources to put the call through, all without disrupting the Boston to San Francisco call.

So by using a peer-to-peer network, a member is taking part in a transaction, using certain network resources while allowing the network to use his or her computer resources. Instead of money, data is exchanged and bandwidth consumed.

Today, Parkes said, peer-to-peer networks function like economies did during the days of bartering for goods. Networking software ensures that for every bit of network resources used by a computer, an equal amount of the computer’s resources are used by the network.

But computer scientists such as Parkes and Pouwelse have been wondering how to get peer-to-peer’s nascent economic system to grow.

One important feature would be to set up an accounting system that tallies the amount of the network’s resources a member used and contributed.

Then, instead of ensuring the resources were always balanced, they could be banked and spent. That would effectively create a new form of currency, Parkes said, in the form of bandwidth or megabyte-sized chunks of data that would be legal tender within the peer-to-peer network.

A video sharing network — whose resources would be in great demand because of the enormous amount of information sent and received in video files — is the perfect candidate on which to try these ideas, Parkes said.

To illustrate how the new economic features would work in Tribler, Parkes and Pouwelse used the example of a group of friends in separate locations collaborating to make a video. Together they build up credits on the peer-to-peer system and then, on a night when they are all working to put the video together, they can use their credits to ensure they have more of the network’s resources available — in the form of faster transmission speeds — than they would otherwise get.

“A network-based system also allows a group of ‘friends’ to pool their collective upload ‘reserve’ to slash download times. In the case of sharing and playing video, that means a true instant, on-demand experience,” explains Pouwelse. “More broadly, this empowers users and groups to run dynamic electronic marketplaces based upon their needs and desires.”

One key to making such a system work is building mechanisms into the network that allow computers to trust each other. Since the tally of network resources used and contributed would be kept on individual machines, there has to be a way to ensure some don’t cheat the system.

The new version of Tribler contains features that allow friends to pool resources, as in the video example above, and to “gossip” about other members, a way of providing feedback that helps build trust.

“It’s a step from a tit-for-tat system towards a currency, but it’s not all the way,” Parkes said.