BitTorrent data throttling might be illegal

"We look forward to responding to any FCC inquiries regarding our broadband network management," said David L. Cohen, executive vice president at Philadelphia-based Comcast.

Comcast denies that it blocks file sharing, but acknowledged after the AP story that it was "delaying" some of the traffic between computers that share files. The company said the intervention was necessary to improve the surfing experience for the majority of its subscribers.

Peer-to-peer file sharing is a common way to illegally exchange copyright files, but companies are also rushing to utilize it for legal distribution of video and game content. If ISPs hinder or control that traffic, it makes them important gatekeepers of Internet content.

The FCC's response will be an important test of its willingness to enforce "Net Neutrality," the principle that Internet traffic be treated equally by carriers. The agency has a broadly stated policy supporting the concept, but its position hasn't been tested in a real-world case.

The FCC's policy statement makes an exception for "reasonable traffic management." Comcast has said its practices fall under that exception.