Edited by John C Tanner
The music and film industries are obviously no fan of peer-to-peer (P2P) file-sharing software like BitTorrent, eDonkey and FastTrack. However, P2P can also cause problems for network operators - and not just of the legal variety.
For a start, P2P traffic is massive, accounting for up to 60% of Internet downstream network traffic, according to recent statistics from CacheLogic. For upstream traffic, it's as high as 70%. Tellingly, the average file size is now 100 MB, compared to 5 MB a few years ago. That might sound like a boon for network operators looking for traffic growth but it's also costly, says CacheLogic co-founder and CTO Andrew Parker.
'P2P clients tend to look for peers with different IP blocks. As a result, 90% of P2P traffic on a service provider's network is going to be crossing transit, which means it's going to be expensive.'
It's also hard on the last mile, he adds. 'P2P is symmetrical, and most ISPs are designed for asymmetrical traffic.'
Since P2P is inevitable, ISPs need a way to manage P2P traffic, says Parker, though he notes that this is a tricky proposition, since P2P clients use ports usually reserved for prioritized IP traffic like VPNs and online games. Consequently, P2P traffic is able to avoid access controls and traffic shaping limitations.
CacheLogic's solution is a bidirectional Layer 7 cache switch that recognizes P2P traffic for what it is. 'You can't manage what you can't see,' Parker says. 'If you can identify P2P traffic, you can identify it by network and hash ID, then save any new content to the cache. Then the next time an eDonkey user tries to download that file from another peer, the network can terminate the connection from the node serving that content and deliver it to the user from the cache.'
Parker claims that ISPs can realize cost savings of up to 40% for transit bandwidth, and up to 60% savings in the last mile, depending on local bandwidth costs.
P2P - the new VOD‾
In any case, ISPs are going to have to think of something. P2P is not going away anytime soon. In fact, for all its reputation as a piracy haven, P2P has also proven itself as a very efficient way of distributing content, legal and otherwise, to the point that some content providers are already starting to see P2P as a potential revenue enabler.
For example, the UK's BBC is trialing a service called iMP, which uses proprietary P2P technology to allow viewers to download BBC programs a week after they air and share them with others - provided they have an iMP player - for seven days until the program 'expires'. Eventually, the BBC plans to make programs available for download the same day they air.
In essence, the BBC chose P2P rather than streaming because it's cheaper. Meanwhile, a small but growing number of pay-TV operators are looking at the possibilities of P2P as an interactive add-on service for providing access to user-generated content, or even as a basic VOD model.