Cachelogic Research paints an interesting picture of decentralized filesharing.

The most astonishing item is that global Internet traffic analysis in June 2004 revealed that in the United States peer-to-peer represents roughly two-thirds of traffic volumes, and in Asia peer-to-peer represents more than four-fifths of traffic volumes. By comparison, HTTP is less than a tenth of the traffic in Asia and less than a sixth of the traffic in the United States. CacheLogic calls peer-to-peer the killer application for broadband with a global reach and a global user base.

Perusing the architectures and protocols section of CacheLogic’s site we find a table comparing the characteristics of web traffic (HTTP) with those of common peer-to-peer protocols. They point out that first generation p2p systems were centralized like Napster; second generation p2p systems were decentralized like Gnutella; and now

The third generation architecture is a hybrid of the first two, combining the efficiency and resilience of a centralized network with the stealth characteristics of distributed/decentralised network. This hybrid architecture deploys a hierarchical structure by establishing a backbone network of SuperNodes (or UltraPeers) that take on the characteristics of a central index server. When a client logs on to the network, it makes a direct connection to a single SuperNode which gathers and stores information about peer and content available for sharing.

Recent developments in peer-to-peer include dynamic port selection and bidirectional streaming of download traffic in the most popular peer-to-peer applications in 2004, BitTorrent (more useful thanks to many available BitTorrent clients and DV Guide) and eDonkey (and eMule). BitTorrent is by traffic the most popular peer-to-peer application:

BitTorrent’s dominance is likely to be attributed to two factors: the rise in popularity of downloading television programmes, movies and software; and the size of these files – a MP3 maybe 3-5Mb while a BitTorrent often sees files in excess of 500Mb being shared across the Peer-to-Peer network.

The high usage of eDonkey in Europe can be attributed to the fact that the eDonkey interface is available in a number of different languages – French, German, Spanish, etc.

So even though the hype machine has stopped pumping p2p, the quieter revolution of the last few years has shown that peer-to-peer traffic has steadily grown to a majority of the Internet traffic worldwide.