Comcast said it plans to limit its residential customers' broadband use, beginning in October.

The company has recently faced scrutiny from the Federal Communications Commission and other critics for its network management practices, which included blocking some applications. After defending itself against accusations that it unfairly targeted peer-to-peer file-sharing, Comcast promised a "protocol agnostic" approach to network management.

This week, Comcast announced that it would phone customers who transfer more than 250 gigabytes of data each month. The company plans to ask those users to cut back.

As the announcement came out, Comcast explained that it wasn't a change in policy. The company said it is simply clarifying the gigabyte limit after customers who received calls asked for a specific threshold for data usage.

The limit will appear in an amended Acceptable Use Policy, which takes effect Oct. 1.

While announcing the limit, Comcast said the median monthly average for data use among its customers is about 2 or 3 GB. To reach the 250 GB threshold, a customer would have to send 50 million e-mail messages (at 0.05 KB), download 62,500 4 MB songs, download 125 standard movies (2 GB each), or upload 25,000 high-resolution photos (10 MB each), Comcast said.

The company will notify customers who exceed the limit that their use is excessive. It will tell customers just how much bandwidth they used. Most customers curb use when asked, the company said.

Comcast said it has begun to spread the word through a notice on its Web site, Twitter, bill stuffers, and a banner on the Comcast.net homepage.