Cable modem
A cable modem is a special type of modem that is designed to modulate a data signal over cable television infrastructure.
The term cable internet (or simply cable) refers to the delivery of Internet service over this infrastucture.
Cable modems should not be confused with older LAN systems such as 10base2 or 10base5 that used coaxial cables.
Cable modems are primarily used to deliver broadband internet access, taking advantage of unused bandwidth on a cable television network.
Along with Digital subscriber line technology, cable modems ushered in the age of broadband internet access in developed countries. Prior to the availability of such systems, Internet access involved slow dial-up access over a public switched telephone network.
Users in a single locality share the available bandwidth provided by the single coaxial cable in the neighborhood. Therefore, depending on the how many users are using the service at the same time (a concept known in technical circles as contention), Internet connection speeds can vary from tens of megabits to a few kilobytes per second.
Often the idea of a shared line is seen as a weak point of cable Internet. From a technical point of view, all networks, including DSL services, are sharing a fixed amount of bandwidth between a multitude of users -- but because cable networks tend to be spread over larger areas than DSL services, more care must be taken to ensure good network performance. Planned well, a cable network can have better performance than a DSL system. Planned poorly, it can be outperformed by a DSL network. It all depends on how much effort the service provider puts into maintaining a quality network.
A more significant weakness of cable networks using a shared line is a loss of privacy, especially considering the recent increase in hacking tools for cable modems. This issue can be addressed by encryption, but again, it depends on a commitment from the provider to maintain a quality network.
One more weakness of cable internet is that it is much harder to self install than DSL. Since a PC is generally located near a phone jack, self-installation of DSL is generally quick. With cable internet, you must either wait for the cable provider to install a new line, or you may have to splice the wires yourself.
Cable modems most commonly use DOCSIS standard (Data Over Cable Service Interface Specification).
See also
Cable modem manufacturers
