September 20, 2007

New P2P network uses bandwidth as currency

Author: Mayank Sharma

The only real exchange between peers in a traditional peer-to-peer network is limited to the files being transferred. Tribler is a new P2P network that's introducing social networking concepts to facilitate better interactions between users. Using new algorithms and protocols, Tribler users will also be able to cash in on their generous uploads for faster downloads.

The Tribler software is primarily developed by the researchers in the Delft University of Technology and De Vrije Universiteit Amsterdam. Sven Seuken, a second-year computer science Ph.D. student at Harvard's School of Engineering and Applied Sciences, says, "This year we started a research cooperation between the Tribler group and the Harvard Economics and Computer Science research group to introduce economic methodologies into the Tribler software." Seuken's adviser Prof. David Parkes from Harvard and Dr. Johan Pouwelse from Delft have developed the concept of a "virtual bandwidth currency."

Seuken says a virtual currency system can overcome the shortcomings of the BitTorrent protocol to improve the efficiency of the system. "The classic BitTorrent protocol is limited to the tit-for-tat mechanism," says Seuken, "meaning a user normally has to upload a file piece when he wants to download another piece." The problem is aggravated when you consider that many Internet connections are asymmetric, with download and upload speeds that can differ by as much as 4:1. This, says Seuken, becomes a problem when a user is downloading a file with the tit-for-tat mechanism; he can never use his full download capacity, because his limited upload capacity doesn't allow him to engage in any more tit-for-tat trades.

Furthermore, this system offers no incentive for users to upload once they have finished downloading, so many users turn off their file sharing client when they are done. By introducing a virtual currency, Tribler hopes to alleviate this problem. Users can earn currency for uploading, and they can spend it at a later time for fast downloads. Every user records his individual trade interactions with other peers, and using the BarterCast algorithm, this information is forwarded to other peers in the system. "Over time, a decentralized trust graph emerges that allows all users of the system to trade with the virtual currency."

Tribler also uses the social networking concept of connecting users in virtual friend circles to help download files. When downloading files, a group of users that are connected to each other sharing the same file are part of a "swarm." When a user from this swarm asks his friends for help, they get the information about which BitTorrent swarm he is currently working with and which file pieces are missing. "They can then join the same swarm as their friend, by downloading the same file, and then forward the pieces they have downloaded to their friend 'for free,' effectively donating upload bandwidth to him," Seuken says.

Linux clients available

Tribler offers clients for Windows, Mac OS X, and Linux. There are two Tribler feature-identical clients available, depending on whether your Internet connection is symmetric or asymmetric. Ubuntu users get a binary package to install Tribler, while other Linux users have to install from the source. Tribler depends on Python-wxGTK2.6, Python-m2crypto, VLC media player, ffmpeg, and Tor. The Ubuntu client has a bug that prevents files found on the network from being displayed, but there's a fix available.

In addition to using it as a P2P client, you can use Tribler as a regular BitTorrent client. It can find torrents automatically, or you can download torrent files from torrent Web sites. The currency concept works irrespective of where the torrent files come from. However, the currency concept will only work between Tribler users or users with compatible clients using the BarterCast and Give-to-Get algorithms.

Tribler lacks any content filtering features. "Tribler is an open P2P system and users can spread what they want, with the same (lack) of privacy as in BitTorrent," Seuken says.

Ongoing research

In addition to making friends, Tribler has a few other features adopted from social networking concepts. The project has just started a top-ten uploader list that lets users know which users are contributing the most to the P2P system.

Seuken says the developers are working on many important research topics at the same time, and in every new software release, new features will be implemented. "The feature with the largest impact will be the fully decentralized trust system. On top of the BarterCast algorithm, we are working on a protocol that makes the virtual currency trading secure, thus preventing fraud and attacks. Once operational, the download speed in P2P file sharing systems could easily be twice or three times as fast, if all users adopt the Tribler client or use compatible protocols." The team is also working on integrating more social network technology in the next version of Tribler -- for example, a chatting function for Tribler users to communicate with each other.

The Tribler project takes an interesting approach, mixing social networking concepts with peer-powered download networks. Already there's a lot of content on the network. With a number of unique features available and more still under development, Tribler has all the ingredients to redefine P2P networks.


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