A new report published by Northwestern University and Telefónica Research discovered some BitTorrent trends worth sharing. During a 2-year period the researchers monitored an unprecedented sample of 500,000 people in 169 countries. Aside from showing that BitTorrent users download more and more data, the report also finds that large ISPs including Comcast are actually making money off BitTorrent traffic.

For more than half a decade many Internet providers have throttled or even banned BitTorrent traffic on their networks. A claim often heard from ISPs is that heavy users are using too much resources and bandwidth.

However, a new report just published (pdf) by Northwestern University and Telefónica Research shows that for larger ISPs there’s an upside to BitTorrent as well. In fact, these companies make a substantial amount of money from BitTorrent traffic.

The goal of the research was to understand the network impact of BitTorrent, both in terms of traffic and the costs involved. To answer this question the researchers conducted a 2-year study where they tracked the downloads of 500,000 people for 169 different countries. The end result is an interesting trend report which, among other things, shows how BitTorrent traffic has developed over time.

For instance, the research found that the average download volume per user per hour increased by 25 percent between November 2009 (110 MB/hour) and November 2010 (139 MB/hour). The number of unique users on the other hand dropped by 10 percent, possibly because people finish their downloads faster. In total the absolute volume of BitTorrent traffic increased by more than 12 percent from 2009 to 2010.

Aside from these general BitTorrent trends, the researchers also looked at the directions BitTorrent traffic are taking. Surprisingly, they find that BitTorrent traffic stays very local. A third of all traffic (32%) does not leave the country of origin and an additional 41 percent only travels to one other country. The researchers further find that the majority stays in local lower tier networks.

The above has some very interesting implications for the costs of BitTorrent traffic for various ISPs.

The researchers translated their findings into the actual costs and revenues of Internet providers and found that contrary to what the public would expect, large Tier 2 ISPs actually make money off BitTorrent traffic. This means that companies such as Comcast, Virgin Media and France Telecom profit directly from heavy downloaders.

“Using inferred business relationships between ISPs, we showed that most BitTorrent traffic flows over cost-free paths and that it generates substantial revenue potential for many higher tier ISPs,” the researchers write.

But not all Internet providers make money off BitTorrent; those in the lower tiers where most traffic is flowing through have less local (and free) traffic and often have to pick up the bill.

“Unlike with tier 2, provider traffic is larger than customer traffic for tier 3, indicating that these ISPs on average are paying for rather than profiting from transit charges due to BitTorrent traffic,” state the researchers.

The report shows that BitTorrent traffic has very a different impact depending on the place an ISP has in the network. Higher tier companies mostly profit from BitTorrent downloads, while lower tier companies are charged for the downloading habits of their consumers. According to the researchers the Internet providers should be aware of the impact BitTorrent has on them, as it may greatly impact their business decisions.

The fact that ‘local’ BitTorrent traffic is preferable is not a new idea. Attempts to keep P2P transfers within the local network as much as possible are not new, and some ISPs have secretly tested the concept in the wild by seeding their own BitTorrent downloads.

As a closing remark we have to note that the study only looked at bandwidth, and not the various other costs BitTorrent traffic has on a network by making millions of connections every day. The takeaway message, however, is that in terms of revenue there are quite a few very large companies that profit directly from heavy BitTorrent users. That’s a conclusion we haven’t heard before.