American Telephone & Telegraph

(RBOC) is a term describing one of the U.S. regional telephone companies (or their successors) that were created as a result of the breakup of American Telephone and Telegraph Company (AT&T, known also as the Bell System or "Ma Bell") by a U.S. Federal Court consent decree on December 31, 1983. The seven original regional Bell operating companies were Ameritech, Bell Atlantic, BellSouth, NYNEX, Pacific Bell, Southwestern Bell, and US WEST. RBOCs are generally in competition for digital data and Internet traffic with wireless service providers and cable TV companies. RBOCs are gradually making available new telephone carrier technologies such as ISDN and DSL.


An ILEC (incumbent local exchange carrier) is a telephone company in the U.S. that was providing local service ILECs include the former Bell operating companies which were grouped into holding companies known collectively as the regional Bell operating companies (RBOCs). A "local exchange" is the local "central office" of an LEC. Lines from homes and businesses terminate at a local exchange. Local exchanges connect to other local exchanges within a local access and transport area (LATA) or to interexchange carriers (IXC) such as long-distance carriers AT&T, MCI, and Sprint.


In the United States, a CLEC (competitive local exchange carrier) is a telephone company that competes with the already established local telephone business by providing its own network and switching. It is very beneficial, especially for ISPs, who may easily get access to the copper loops and other switching elements necessary to provide xDSL services.


A Multiple Systems Operator (MSO) is a company that has acquired multiple CATV systems and brought them under the control of a single corporate entity. The individual CATV systems may or may not have been combined into a single network, or may have been combined at a regional or metropolitan level. The largest MSOs include Comcast, Time Warner Cable, Cox Communications, Charter Communications, Cablevision Systems, Bright House Networks LLC, Suddenlink Communications, Mediacom Communications Corporation, and Insight Communications.

As of June 2007, the largest cable system operated by an MSO was operated by Cox Communications, with over 800,000 subscribers. This one system is larger than most MSOs. In fact, Cox has three of the five largest cable systems, including San Diego, California and Las Vegas, Nevada.


An ISP (Internet service provider) is a company that provides individuals and other companies’ access to the Internet and other related services such as Web site building and virtual hosting. An ISP has the equipment and the telecommunication line access required to have a point-of-presence on the Internet for the geographic area served. The larger ISPs have their own high-speed leased lines so that they are less dependent on the telecommunication providers and can provide better service to their customers.

The largest national and regional ISPs are AT&T WorldNet, IBM Global Network, MCI, NetcoISPs also include regional providers such as, UUNet, and PSINets New England's NEARNet and the San Francisco Bay area BARNet.

ISPs are responsible for providing Internet connectivity and maintaining the network infrastructure. Some ISPs also provide hardware and, in the case of cable Internet, handle the task of installing the service in a customer's home or office. In addition, the ISP provides technical support. ISPs also work with law enforcement from time to time, providing information about an account or IP address to the authorities when a user is suspected of a crime.