The Comcast Corporation plans to slow service to its heaviest Internet users during periods of congestion after regulators ordered the company to devise a new method for managing its Web traffic.

Top Internet speeds for the heaviest users will be reduced for 10 to 20 minutes to keep service to other users flowing, said Mitch Bowling, Comcast’s senior vice president and general manager for online services.

The Federal Communications Commission found on Aug. 1 that Comcast had improperly blocked peer-to-peer programs like BitTorrent that are used to share video and other files.

In an order posted on its Web site on Wednesday, the F.C.C. gave the company 30 days to provide details of its “unreasonable network management practices” and show how they would be changed by year-end.