The CATV (Cable Television) Data Network Explained

More than just TV

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 and phone service over the same CATV lines.

CATV Infrastructure

Cable providers 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.

DOCSIS

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 been improved gradually over the years:

  • DOCSIS 1.1 (1999): Added quality of service (QoS) capability necessary to support voice over IP (VoIP), a technology that allows voice communications over an internet connection
  • 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
  • DOCSIS 3.1 Full Duplex (2016): Initiated ongoing innovation project to enable the full usage of resources for equivalent upstream and downstream speeds while maintaining backward compatibility with earlier DOCSIS versions

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 broadband routers or other devices to their internet service. Home networks also can 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 to receive cable internet. Many providers offer multiple choices of plans ranging from low to high end. These are a few of the key considerations:

  • Plans that combine cable internet, cable television, and telephone service into a single contract are called bundled packages. So-called triple-play packages include all three. Although 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 limit the amount of data that can be generated during each billing period (normally, monthly) while some offer unlimited data.
  • Most providers offer cable modem rentals for an additional fee for customers who prefer not to buy them.

CATV Connectors

To hook up a television to cable service, the user must plug a coaxial cable 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, also called a CATV connector; these are same connectors that were used with analog TV setups over the past few decades before cable TV existed.

Photo of Screw-on Type RF Coaxial Cable
RF Coaxial Cable - Screw-on Type. Photo © Robert Silva - Licensed to About.com

CATV vs. CAT5

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.