Comcast Corp.'s interference with Internet traffic has prompted a federal investigation and is at the center of calls for network neutrality laws, but another U.S. cable company appears to be doing the same thing without drawing scrutiny.
Of the 788 Comcast subscribers who participated in the study, 62 percent had their connections blocked. At Cox, 54 percent of subscribers examined were blocked, according to Krishna Gummadi at the Max Planck Institute for Software Systems in Saarbruecken, Germany. The institute examined the network connections of 8,175 Internet subscribers around the world.
Comcast is the country's second-largest Internet service provider, with 14.1 million subscribers. Cox is the fourth-largest, with 3.8 million; it is part of privately held Cox Enterprises Inc.
Comcast's practice of interfering with traffic was brought to light by user reports last year and confirmed by an Associated Press investigation in October.
Consumer advocacy groups and legal scholars criticized the interference, saying that letting a service provider selectively block some connections makes it a gatekeeper to the Internet, violating the network's open principles. Their complaints prompted the Federal Communications Commission to start an investigation, which is ongoing.
Legislation also has been introduced in Congress to guarantee net neutrality, or equal treatment of traffic by Internet service providers.
"This research proves beyond a shadow of a doubt that consumers, Congress and the FCC must urgently pursue the complaints against network providers," said Ben Scott, policy director of Free Press, one of the groups that urged the FCC to fine Comcast.
File-sharing programs like BitTorrent, which let people exchange documents, songs, movies and other content, can be heavy users of Internet bandwidth.
Comcast maintains that hampering such programs helps ensure that traffic other than file sharing is not impeded by a few big users. The company says that it is delaying file transfers rather than blocking them. Even that will end later this year, Comcast said in March, as it pledged to stop the practice.
At least since 2006, Cox's subscriber agreement has noted that the company engages in "protocol filtering," which means it treats different types of Internet traffic, like Web surfing, e-mail and file sharing, differently.
Cox said Thursday that it takes such steps "to ensure the best possible online experience for our customers." But Cox denied that protocol filtering amounts to discrimination of any specific services.
The blocking observed by Gummadi's group occurs when a subscriber has downloaded a file using the BitTorrent application and tries to upload it, or share it with others, over the Internet. The main victims are the other Internet subscribers, who will not be able to download a file if a complete version is not available from someone else's computer.
Persistent attempts by file-sharing software to get through an Internet service provider's filtering may succeed after several minutes, as experienced in the Associated Press test last year. But Gummadi's test did not look at the duration of the traffic blocks.
Gummadi found signs of interference at seven other U.S. Internet providers, all of them cable companies.
© 2008 Associated Press