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Last Updated: Monday, 20 June, 2005, 09:44 GMT 10:44 UK
Microsoft works on own BitTorrent
Desperate Housewives
Shows like Desperate Housewives are in huge demand on file-sharing sites
Microsoft researchers in Cambridge, UK, are developing their own peer-to-peer file-sharing software.

Codenamed Avalanche, the program makes it easy to share content by dividing files such as software, audio or video, into chunks, much like BitTorrent.

Using "network coding", it can re-create missing blocks of data that can be used in place of missing chunks.

The reputation of file-sharing has been damaged by legal action after it was adopted to share copyrighted files.

BitTorrent uses

In BitTorrent systems, server sites do not host the files being shared. They host links, called "trackers" that direct people to where they can download the pieces of a file instead.

Since December, the Motion Picture Association of America (MPAA), representing the global movie industry, has been targeting BitTorrent sites because they have been used to share copyrighted material.

By leveraging desktop PCs, Avalanche aids in the distribution process, relieving congested servers and network links from most of the traffic
Microsoft researchers
The action, and the threat of action, has forced many of them to shut down.

Such sites say they can not be held responsible for people who use the technology to distribute illegally-copied content.

Peer-to-peer file-sharing is being adopted for downloading and distributing legitimate content.

The BBC is currently trialling an interactive media player (iMP) based on file-sharing technology to let people download programmes they have missed up to seven days after it is first broadcast.

Microsoft researchers said Avalanche could be used to help distribute software, security patches, as well as content like TV-on-demand.

"Avalanche provides a cost effective, internet scalable and very fast file distribution solution," say the researchers on their website.

"By leveraging desktop PCs, Avalanche aids in the distribution process, relieving congested servers and network links from most of the traffic."

Swarming and magic

Peer-to-peer systems use what is called "swarming techniques" to distribute files.

This means after a file is divided into smaller pieces of data, the parts are downloaded from different nodes, or sources.

But unlike BitTorrents, Avalanche does not depend on trackers. The Avalanche program on each computer shares the files automatically, without having to search a user's hard drive.

Screengrab from LokiTorrent website
The MPAA has been trying to close down BitTorrent websites
The problem with many file-sharing applications is that not all the pieces to make a complete file may be obtainable.

Sometimes there is heavy demand on the file-sharing network, which can slow download times, when people try to find missing parts.

Through its network encoding, Avalanche is designed to rebuild the required part of a file once it has enough other pieces of a file to work on; this means Avalanche can turn any part of a file into what it needs.

Avalanche would also make it harder to files to be corrupted, say the researchers.

Microsoft says that the system stops people re-distributing content because it will only forward files that have been "signed" by the publisher.

The researchers say they are in talks with other companies about Avalanche and it could be turned into a product soon.

The movie, music and TV industries are keen to clamp down on file-sharing programs because they say they are responsible for much of its lost revenue.

But fans of the technology argue that file-sharing is a sensible way to distribute legitimate content, without putting pressure on servers and networks.

In recent research, web tracking company Envisional said downloads of TV programmes had increased by 150% in the last year. About 70% were using BitTorrent to get files, the firm said.

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