The CATV (Cable Television) Data Network Explained

Ethernet cables going into a cable modem.
Jill Ferry Photography / Getty Images

CATV is a shorthand term for cable television service. The same cabling infrastructure that supports cable TV also supports cable Internet. Many internet service providers (ISPs) offer their customers cable Internet service together with television over the same CATV lines.

CATV Infrastructure

Cable providers either operate directly or lease network capacity to support their customers. CATV traffic typically runs over fiber optic cables on the provider's end and over coaxial cables on the customer's end.


Most cable networks support the "Data Over Cable Service Interface Specification" (DOCSIS). DOCSIS defines how digital signaling over CATV lines works. The original DOCSIS 1,0 was ratified in 1997 and has gradually been improved over the years:

  • DOCSIS 1.1 (1999): Added Quality of Service (QoS) capability necessary to support voice over IP (VoIP)
  • DOCSIS 2.0 (2001): Increased data rates for upstream traffic
  • DOCSIS 3.0 (2006): Increased data rates and added IPv6 support
  • DOCSIS 3.1 (2013+): Greatly increased data rates

To get the full feature set and maximum performance from cable internet connections, customers must use a modem that supports the same or higher version of DOCSIS their provider's network supports.

Cable Internet Services

Cable internet customers must install a cable modem (typically, a DOCSIS modem) to hook their home broadband router or other devices to the Internet service. Home networks can also use cable gateway devices that combine the functionality of the cable modem and broadband router into a single device.

Customers must subscribe to a service plan in order to receive cable internet. Many providers offer multiple choices of plans ranging from low end to high end. Key considerations include:

  • Plans that combine cable internet, cable television and sometimes telephone service into a single contract are called bundled packages. So-called "triple play" packages include all three. While the cost of bundled packages exceeds that of internet service alone, some customers save money by keeping their subscriptions with the same provider.
  • Some cable internet services place maximum limits on the amount of data that can be generated during each billing period (normally, monthly) while some offer unlimited data.
  • Cable modems can normally be rented for an additional fee rather than purchased separately

CATV Connectors

To hook up a television to cable service, a coaxial cable must be plugged into the TV. The same type of cable is used to connect a cable modem to cable service. These cables use a standard "F" style connector often called a CATV connector, although these are same connectors that were commonly used with analog TV setups over the past few decades before cable TV existed.


Despite the similar naming, CATV is not related to Category 5 (CAT5) or other types of traditional network cables. CATV also traditionally refers to a different kind of television service than IPTV.