Cable Internet (DOCSIS)

What It Means

Cable internet uses the Data Over Cable Service Interface Specification (DOCSIS), a standard originally developed by CableLabs in 1997 and iteratively upgraded to support broadband over the same coaxial infrastructure originally built for cable television. DOCSIS 3.0, which still serves the majority of U.S. cable subscribers, supports up to roughly 1 Gbps download and 50 Mbps upload. DOCSIS 3.1, the current deployment standard, pushes theoretical maximums to 10 Gbps down and 1 to 2 Gbps up, with real-world consumer plans typically capped at 1.2 to 2 Gbps down. Cable is the most widely available broadband technology in the United States, with Comcast Xfinity serving roughly 32 million residential subscribers and Charter Spectrum serving about 30 million, together controlling over 55% of fixed broadband subscriptions. The primary weakness of cable is that it is a shared medium: a single neighborhood node may serve 200 to 500 homes drawing from the same upstream pipe, so speeds can drop 20 to 40% during evening peak hours between 7 and 11 PM. Upload asymmetry is the second weakness, a 1,000 Mbps cable plan typically offers only 35 Mbps upload, which hurts remote workers running video calls and cloud backups. The Broadband Grade treats cable as a mid-tier technology, better than DSL but below fiber. DOCSIS 4.0, which promises symmetrical multi-gigabit service, began limited deployment in 2024 and will close the performance gap with FTTH over the next several years.

Frequently Asked Questions