Which Cable Modem Do I Need for High-Speed Internet?

Research consortium CableLabs developed Data-Over-Cable Service Interface Specifications (DOCSIS) as a standard for cable Internet communication devices. These devices include cable modems and cable company hardware. DOCSIS standards ensure that cable companies' hardware can communicate with private users' cable modems. Cable companies can choose to accept DOCSIS standards so that users can purchase any DOCSIS modem, but they can also choose to use proprietary systems, meaning end-users have to purchase cable company-approved or -provided devices.

In December 2010, the National Cable Television & Telecommunications Association listed Comcast as the nation's top Multichannel Video Programming Distributor, with the most basic subscribers in the United States. Basic Comcast users can use any DOCSIS compliant modems. Comcast users subscribing to Performance, Blast!, Ultra or Extreme cable services, which provide different tiers of data transfer speed, must be careful to use modems with appropriate version numbers for the corresponding speed tier. Comcast provides users with this information.

Time Warner is the second largest cable provider in the United States in number of subscribers. Like Comcast, Time Warner also offers cable Internet service. Time Warner's cable Internet service is DOCSIS compliant. Time Warner users simply need to purchase a DOCSIS compliant modem, though Time Warner does not guarantee that a user-purchased modem always work with its broadband service.

The third largest cable company, Cox, also adheres to DOCSIS standards. DOCSIS compliant modems should work with Cox cable Internet service, but Cox only provides a small list of approved modems on its website. The website also includes a disclaimer that modems not on its list may not work with Cox Internet service.

Comcast, Time Warner and Cox all allow users to purchase modems from a retailer, but they also lease modems to their customers. These leased modems are guaranteed to work with each corresponding service provider, but the are supplied for an additional service fee. They also remain property of the cable company and may have to be returned if users discontinue their Internet service.