AT&T is going to implement bandwidth caps and will begin trials to determine the appropriate cap rates. The first trial is in Reno, Nev.; the company will designate a second trial market before the end of the year.

Several other providers, including Rogers, Comcast and Time Warner Cable, are already implementing bandwidth caps. The issue is figuring out a way to implement the scheme without violating the privacy or discriminating against individual subscribers.

AT&T is relying on the same rationale as other service providers: dealing with bandwidth hogs. AT&T said 5% of its subscribers take up 50% of its capacity.

AT&T plans to limit downloads to 20 gigabytes per month for customers of its slowest DSL tier, at 768 kbps. The limit increases with the speed of the plan, up to 150 gigabytes per month at the 10 Mbps tier. Exceeding the limit will cost $1 per gigabyte.