One of the most detailed examinations to date of actual peer-to-peer traffic, the CacheLogic survey used network-monitoring tools installed inside top Internet service providers (ISPs) to capture data packets and identify whether they had been sent by programs such as Kazaa or Gnutella.
Over six months of surveying, the British company found that Kazaa use had slipped far behind rival BitTorrent, which accounted for 53 percent of actual peer-to-peer network traffic. It found also that overall traffic has not been falling, as some have suggested. By June, an average of 8 million users were online at any given time, sharing a petabyte (10 million gigabytes) of data.
"The overall level of file sharing has increased," said Andrew Parker, CacheLogic's founder and chief technology officer. "Users have migrated from Kazaa onto BitTorrent."
The company's observations add to what have beenunder way in the peer-to-peer world, with computer users increasingly downloading big files such as movies and software, and reducing reliance on onetime file-sharing king Kazaa.
Reliable statistics on the file-sharing networks have always been difficult to come by, since most trades takes place directly between two individuals, and many surveys have relied on computer users' cautious descriptions of their own behavior.
Other recent surveys have noted a rise in the use of eDonkey, with a decline or a plateau in the use of Kazaa and related software.
Network monitoring firm BayTSP said Monday that the average number of people on the FastTrack network, which is dominated by Kazaa, held steady in June at about 2.7 million users at any given time. eDonkey, use of which has risen sharply in the last year, held at about 2.2 million average users, the company said.
BitTorrent has typically been harder to track than its rivals. Like Napster before them, Kazaa and eDonkey each allow people to tap into a vast network of connected computers, searching for a given file. The size of that network can be estimated by outsiders.
But BitTorrent works by --say, the latest episode of "The Sopranos." Because each file has its own network, it is much harder to estimate how widespread use of the software has been.
Other surveys have also recently said that movie swapping has been rising. Most recently,said that about 24 percent of Internet users had downloaded a feature-length film online at least once, and that these downloaders had averaged about 11 films each.
Some critics said the MPAA findings were suspect, since their sample had been weighted strongly toward broadband subscribers who were active moviegoers, rather than the general population.
CacheLogic's focus on the traffic, rather than number of users, may overstate the lead that BitTorrent has on its rivals. That software was designed from the beginning for efficient distribution of very large files, and is even used by open-source companies to distribute free versions of the Linux operating system.
Kazaa, by contrast, is less efficient for big files, and may be used more widely to trade MP3 music files, which can be a hundredth the size of a movie file.
Parker said that his company had operated 12 network monitoring devices in top-level ISP networks around the world, each handling a few gigabits per second of data. The devices sit in the stream of Internet traffic and mirror the data flow, identifying the program or Internet Protocol used to send each bit of information.
They do not look at actual contents of the data stream itself, and so the company is unable to determine which files are movies or software programs, for example.
The company plans to sell its network and traffic management tools to ISPs beginning later this year.