Microsoft works on own BitTorrent
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 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.


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.


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.

Story from BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/1/hi/technology/4110302.stm

Bram Cohen Lambastes Avalanche

"First of all, I'd like to clarify that Avalanche is vaporware," Bram Cohen writes in his weblog. "It isn't a product which you can use or test with, it's a bunch of proposed algorithms. There isn't even a fleshed out network protocol. The 'experiments' they've done are simulations."

On the surface, Avalanche appeared promising. One of the more frustrating aspects of BitTorrent is that many times, file transfers slow down to a crawl towards the end. This happens when the sources of information begin to dry up. Avalanche proposed a type of "Par file" error correcting system. During BitTorrent transfers, a file is broken up into many segments. Avalanche proposed that each segment of a file will be encoded with an error correcting code. Once enough of these codes combined, the file will automatically finish creating itself. Seems like a novel idea, right?

However, Bram Cohen had already covered the topic in November of 2004, in which he responds to repeated requests for the feature.

"It isn't done because, quite simply, it wouldn't help."

Bram goes more into technical detail by presenting three possible benefits, with corresponding rebuttals.

Bram goes on to criticize Avalanches implementation of error correcting.

"The really big unfixable problem with error correction is that peers can't verify data with a secure hash before they pass it on to other peers. As a result, it's quite straightforward for a malicious peer to poison an entire swarm just by uploading a little bit of data. The Avalanche paper conveniently doesn't mention that problem."

Bram continued to rip into the very heart of Avalanche, dismantling most of their proposals. He did however, credit the work on from a more literary point of view.

"As you've probably figured out by now, I think that paper is complete garbage. Unfortunately it's actually one of the better academic papers on BitTorrent, because it makes some attempt, however feeble, to do an apples to apples comparison."
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