AT&T is raising the data caps for U-verse Internet customers to 1TB a month and providing unlimited data "at no additional charge" to customers who subscribe to the company's 1Gbps service.

But DSL users on AT&T's network aren't getting any extra data, and those users must continue to make do with a 150GB monthly limit.

AT&T has been enforcing data caps on DSL users for years but only began enforcement of caps on its faster U-verse service in May this year. Data caps were set at 300GB, 600GB, or 1TB based on the speed tier. But the changes announced today—which take effect August 21—give all U-verse customers a monthly data cap of 1TB or no cap at all. Previously, a 1TB cap was only for customers with speeds from 100Mbps to 1Gbps.

While 1Gbps customers will be upgraded to unlimited data, U-verse customers with slower speeds can pay $30 extra a month for unlimited data. Customers can also get unlimited data if they sign up for AT&T's U-verse or DirecTV video service.

By imposing data caps only on customers without TV service, AT&T makes it harder for subscribers to ditch traditional TV and use online streaming services exclusively. But the company argued that 1TB is plenty for customers who watch online video. "1TB of data per month is enough for up to 400 hours of HD video streaming per month (or more than 13 hours per day!)," AT&T wrote in its announcement.

As before, customers who exceed the cap will be automatically charged $10 for each additional 50GB allotment. Overage charges for U-verse are capped at $100 per month.

AT&T's announcement today is similar to a recent Comcast decision that raised data caps from 300GB to 1TB in response to extensive criticism from customers.

AT&T's announcement didn't mention DSL users, but a company spokesperson confirmed to Ars that its 150 GB cap on DSL isn't changing. Additionally, DSL users are not provided the option to purchase unlimited data and can be charged up to $200 a month in overage fees rather than the $100 limit for U-verse customers.