By Alina Selyukh WASHINGTON (Reuters) – U.S. cable and fiber Internet providers generally deliver the download speeds they advertise, though not consistently, while DSL connections increasingly fail to meet promised speeds, the Federal Communications Commission said on Wednesday. The agency has been testing download and upload speeds of top Internet service providers (ISPs) yearly since 2011, but this year for the first time also assessed how likely consumers were to get speeds as advertised. The report found Cablevision and Verizon Fiber to be two providers to deliver faster-than-promised download speeds to 80 percent of consumers 80 percent of the time, with Comcast and Frontier Fiber delivering just short of promised speeds. Windstream, Verizon DSL and Frontier DSL delivered download speeds less than 60 percent of what they promised to 80 percent of consumers 80 percent of the time.