Cable Internet access

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In telecommunications, cable Internet access (often called simply cable Internet) is a form of broadband Internet access that uses the cable television (CATV) infrastructure. Like digital subscriber lines and Fiber to the premises, cable Internet access provides network edge connectivity (Last mile access) from the Internet service provider to an end user. It is integrated into the cable television infrastructure analogously to DSL which uses the existing telephone network. CATV networks and telecommunications networks are the two predominant forms of residential Internet access. Recently, both have seen increased competition from fiber deployments, wireless, and mobile networks.

Hardware and bit rates

Broadband cable Internet access requires a cable modem at the customer's premises and a cable modem termination system at a cable operator facility, typically a cable television headend. The two are connected via coaxial cable or a Hybrid Fiber Coaxial (HFC) plant. While access networks are sometimes referred to as last-mile technologies, cable Internet systems can typically operate where the distance between the modem and the termination system is up to 100 miles (160 km). If the HFC network is large, the cable modem termination system can be grouped into hubs for efficient management.

Downstream, the direction toward the user, bit rates can be as much 400 megabits per second for business connections, and 100Mbit/s for residential service in some countries. Upstream traffic, originating at the user, ranges from 384Kbit/s to more than 20Mbit/s. One downstream channel can handle hundreds of cable modems. As the system grows, the cable modem termination system can be upgraded with more downstream and upstream ports.

Most Data Over Cable Service Interface Specification (DOCSIS) cable modems restrict upload and download rates, with customizable limits. These limits are set in configuration files which are downloaded to the modem using the Trivial File Transfer Protocol, when the modem first establishes a connection to the provider's equipment.^[1] Some users have attempted to override the bandwidth cap and gain access to the full bandwidth of the system (often as much as 30 Mbit/s), by uploading their own configuration file to the cable modem - a process called uncapping. Uncapping is almost always a violation of the Terms of Service agreement.^[2]

Shared bandwidth

Like all residential broadband technologies, such as DSL, FTTX, Satellite Internet, or WiMAX, a population of users share the available bandwidth. Some technologies share only their core network, while some including Cable Internet and PON also share the access network. This arrangement allows the network operator to take advantage of statistical multiplexing, a bandwidth sharing technique which is employed to distribute bandwidth fairly, in order to provide an adequate level of service at an acceptable price. However, the operator has to monitor usage patterns and scale the network appropriately, to ensure that customers receive adequate service even during peak-usage times. If the network operator does not provide enough bandwidth for a particular neighborhood, the service can become sluggish if many people are using the service at the same time. Some operators, such as Virgin Media in the UK, use a bandwidth cap, or other bandwidth throttling technique. In the case of Virgin Media, the user's download speed is limited during peak times, if they have downloaded a large amount of data that day.^[3]

Bundled service offerings

Many CATV Internet access providers offer Internet access without tying it to a cable television subscription. Subscription costs are often discounted when bundled with a cable television subscription. The cable TV signals are often removed by filtering at the line tap outside the customer's premises.

See also

• List of cable Internet providers
• Cable modem

References