SEAS Team Launches File Sharing Program

A team from the Harvard School of Engineering and Applied Sciences (SEAS) is currently collaborating on an electronic marketplace for file-sharers that would increase the efficiency of peer-to-peer networks by providing individuals incentives to contribute to the system.

Made available for free download on Aug. 29, the most recent version of the video-sharing software—known simply as “Tribler”—appears to be gaining something of a foothold. Ten thousand downloads were recorded in the first week alone, according to Sven Seuken, a second-year graduate student in computer science who works with the Tribler team.

One of the distinctive features intended to give Tribler a leg up on the competition is its use of an electronic “currency” to address the inefficiencies that have plagued other peer-to-peer systems. Time-honored adages aside, people appear to favor receiving over giving on peer to peer networks. And given the cooperative nature of such systems—everything downloaded has first to be uploaded by someone else—such selfish asymmetry can be crippling.

BitTorrent, which Seuken identified as the most commonly employed peer-to-peer protocol, attacks the problem of inducing downloaders to give by employing a “tit-for-tat” system of barter, in which downloaders are required to share pieces of a file with each other. But the system has its limitations, according to Seuken.

Seuken said he believes this bartering aspect of BitTorrent promotes fairness in the short-term, but when the minute users are done with their immediate download, they stop contributing to the network.

Among Tribler’s distinctive features is a decentralized accounting system that tracks a user’s uploads and downloads to the network, creating a strong incentive to upload in order to accumulate currency that can later be translated into faster downloads in the future. A user may choose to leave his computer on at night, uploading material, so that he can “afford” faster downloads later.

Loeb Associate Professor of the Natural Sciences David Parkes says that the increased efficiency afforded by Tribler and its allowance for users to pool their “currency” to help each other achieve quicker downloads make the new program preferable to BitTorrent and an apt choice for college students.

“Presumably, most Harvard kids are using file sharing clients,” Parkes said. “I can only imagine that everyone is, and the idea here is to be able to do much richer, higher bandwidth conferences over file sharing systems.”

But Tribler’s “currency” feature and its coincident efficiency gains may not be enough to unseat BitTorrent, according to Chen Fang ’10, who worked last year as a User Assistant for FAS Computer Services. Fang says he first encountered the news about Tribler a few weeks ago, while on the popular content-aggregation site digg.com.

Fang, who conceded that “Tribler looks pretty,” said he doubted that students already using stripped-down versions of BitTorrent would make the switch based on the supposed advantages of the currency approach.

For those interested, the Tribler software can be downloaded at http://tv.seas.harvard.edu.

—Staff writer Christian B. Flow can be reached at cflow@fas.harvard.edu.