P2P Research Institute Blog

Peer-to-peer technology has many extremely useful applications. Fundamentally P2P is about increasing network resilience and decreasing bandwidth costs. Privacy, anonymity and security are all secondary to these essential principles. While BitTorrent has been an extremely successful P2P protocol for certain types of P2P applications, such as patch distribution for Blizzard’s World of Warcraft, it has also been a failure in other areas.

The Holy Grail

Streaming video is one of the largest consumers of bandwidth today. Many estimates put it ahead of P2P in terms of gross bandwidth consumption. Sites like YouTube and Google Video attract vast numbers of viewers. Various online video streaming services are starting up, offered by companies like Amazon and NetFlix. It seems that streaming video, and the sales and advertising opportunities which come along with it, represent an irresistible revenue source for large companies.

However, streaming video also has large bandwidth costs associated with it. According to the Wikipedia page on streaming video, to stream a standard video to 1,000 viewers would require 300 Mbit/sec of bandwidth using a traditional unicast approach. All this bandwidth is expensive. How can streaming providers spread this cost out? With P2P. Make your consumers pitch in to host the video. As the number of viewers increases, so should the amount of peers which can serve up the data, allowing you to scale up the number of participants without proportionate increases in your own bandwidth.

Why not BitTorrent

As we have written about before on this blog, BitTorrent is not good for streaming video due to its rarest-first download ordering policy. In order to stream video, or music, or whatever – you want it to arrive in a predictable order. Typically that order is linear, starting at the start. This way data arrives in the order of consumption. But BitTorrent does not provide this. In fact, it almost explicitly guarantees that it will not order data in a linear fashion. BitTorrent trades predictable ordering for replication increases. Under BitTorrent, the rarest pieces of data will be replicated the most, and so become less rare.

So what, then?

Companies are instead developing their own protocols. The EU has given 19 million euro to one P2P group which is modifying the BitTorrent protocol to support streaming – presumably by doing away with the rarest-first policy.

China has a number of well-funded start ups developing their own P2P video streaming technologies. Blin.cn claims to be 50x faster than BitTorrent for video streaming. Google is an investor in Chinese streaming company Xunlei.

And of course BitTorrent, Inc have been working to develop their own video streaming version of their protocol.

Who will come out on top remains to be seen.