A new study from comScore Networks breaks down the Internet Service Providers used by large and small businesses across the U.S., and the two brands atop the list will sound very familiar.

AT&T and Verizon together represent nearly a third of the business ISP market, according to the study. The wireless divisions of the same companies are also the country’s leading mobile carriers.

In the business ISP market, AT&T rules, with 20 percent of all business Internet traffic in September, according to the report. Verizon is No. 3, at 12 percent, followed by CenturyLink (recently merged with Qwest) at 7 percent. Here’s a look at the full ranking.

Like what you're reading? Subscribe to GeekWire's free newsletters to catch every headline

Job Listings on GeekWork

Find more jobs on GeekWork. Employers, post a job here.