Avalanche threatens BitTorrent

Peer-to-Peer (P2P) file sharers who currently use the Bit Torrent distribution method might soon be persuaded to move to Microsoft, because the software giant’s UK-based research arm is in the process of developing a P2P system that it claims will offer faster, more effective file transfers.

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By  Matthew Wade Published  June 21, 2005

Peer-to-Peer (P2P) file sharers who currently use the Bit Torrent distribution method might soon be persuaded to move to Microsoft, because the software giant’s UK-based research arm is in the process of developing a P2P system that it claims will offer faster, more effective file transfers. Although a late arrival into the world of P2P file sharing, Microsoft’s technological approach, codenamed ‘Avalanche’, employs what’s called ‘network coding’ to overcome the scheduling problems associated with Bit Torrent-like protocols. Microsoft’s researchers claim download times are between 20% and 30% per cent faster using network coding than on systems that only code at the server, and between 200% and 300% quicker than distributing information that is completely un-encoded. Avalanche is largely based on the same principles as BitTorrent, in that it breaks up large digital files up into smaller pieces, to make them easier to share between many users. The recurring niggle with the BitTorrent approach however is that the downloader might have a long wait before the final piece of a file becomes available. As the number of receivers increases, the task of scheduling traffic also gets more complex, which in turn slows the whole process. Microsoft’s Avalance approach still breaks data into small, easy to transfer packets to accelerate downloading, but includes details on all the other pieces of data in each file too. Put more technically, Avalance re-encodes all the pieces of a file, so that each shared piece is actually a linear combination of all the pieces, fed into a particular function. Each distributed block includes a tag, which in turn describes the parameters that that particular block contains. This means that once a user has downloaded several blocks, they can generate new combinations from those they have, and subsequently send those out to their peers. If a user collects enough pieces, they’ll have enough information to reconstruct the entire digital file in question (even if they don’t have all the original pieces). The key point here is that peers (the downloaders of a file) can make use of any new part of that file, instead of having to wait for specific missing chunks. This means no one peer can become a bottleneck, since no piece is more important than any other. It also reduces the amount of overall network traffic, as the same info doesn’t have to travel back and forth several times. Users in need of more info should check out Microsoft Research’s Avalanche briefing PDF at www.research.microsoft.com/~pablo/papers/nc_contentdist.pdfAlso visit http://research.microsoft.com/~pablo/avalanche.htm. Even though this type of P2P protocol may, at first, seem to have ‘dodgy downloaders walk this way’ written all over it, Microsoft doesn’t want to be seen to be promoting or developing any technology that might be used for illegal purposes. Thus its press material stresses that Avalanche should only be used for distributing legitimate content. In fact, it’s predicted that Avalanche might work better with users and copyright holders than BitTorrent, as it could include a digital rights management (DRM) system that only allows users to redistribute content with prior approval from publishers. Time will tell whether this feature will Avalance’s popularity with downloaders, though it certainly might position Avalanche as the P2P distribution method of choice for TV on-demand download services, and patch and software distribution. According to an anonymous Microsoft researcher, quoted on www.infoworld.com, Avalanche could be introduced to users in the UK as early as next year. At present no details of Middle East timings are available.

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