As much as two-thirds of the traffic that ISPs carry today is from peer-to-peer Web sites, and most of that traffic is caused by users downloading massive DVD files.

That's the assessment of ISP traffic patterns offered by Yuval Shahar, CEO of P-Cube. P-Cube is a venture-funded start-up that sells network devices to help ISPs throttle back peer-to-peer traffic.

"What we see today is that close to 70% of the traffic is peer-to-peer," Shahar says. "And that's not just residential traffic. We see peer-to-peer usage at work, too."

Shahar says peer-to-peer traffic is shifting from users swapping small MP-3 music files to users simultaneously downloading multiple movies. This trend is putting pressure on ISPs to segment their traffic to make sure peer-to-peer applications don't consume all of the available bandwidth.

"Napster was about swapping MP-3 files. Now it's mostly DVD movies, and the typical file is over 700M-byte. Users will set up 10 or 20 of those downloads in the background," Shahar says.

P-Cube in May upgraded its SE2000 network device and Engage 2.1 software to provide ISPs with better controls for limiting the amount of bandwidth available to peer-to-peer applications.

The SE2000 analyzes Internet traffic from the point of view of user sessions instead of packets.  The latest version can handle throughput up to 4G bit/sec, and it offers improved availability and redundancy. The latest version of the company's Engage software adds protection against denial-of-service attacks. 

Interoute, a Pan-European ISP, is using P-Cube's newest devices to sell bandwidth that is guaranteed to be peer-to-peer free at a premium price. Other ISPs are using P-Cube's devices to set limits on how much of their bandwidth can be consumed by peer-to-peer traffic.

"Carriers can use [the SE2000] to create different qualities of service and different service levels," Shahar says. "They could even add dedicated management for VoIP or video conferencing once they have the session-based management capability."

Founded in 1999, P-Cube has raised $70 million in financing from such big-name venture firms as Accel Partners, ComVentures and Venrock. Among the 40 ISPs that use P-Cube's devices are Interoute, Singapore Telecom, Korea Telecom and NTT.