RBOCS-The Regional Bell Operating Companies (RBOC) are the result of United States v. AT&T, the U.S. Department of Justice antitrust suit against the former American Telephone & Telegraph Company (later known as AT&T Corp.). On January 8, 1982, AT&T Corp. settled the suit and agreed to divest its local exchange service operating companies. Effective January 1, 1984, AT&T Corp.'s local operations were split into seven independent Regional Bell Operating Companies known as "Baby Bells". RBOCs were originally known as Regional Holding Companies (RHCs). Currently, three companies have the RBOCs as predecessors. They are AT&T Inc., Verizon, and Century Link. Some other companies are holding on smaller segments of the companies.
ILEC- An incumbent local exchange carrier (ILEC) is a local telephone company in the United States that was in existence at the time of the breakup of AT&T into the Regional Bell Operating Companies (RBOCs), also known as the "Baby Bells."[1] The ILEC is the former Bell System or Independent Telephone Company responsible for providing local telephone exchange services in a specified geographic area. GTE was the second largest ILEC after the Bells, but it has since been absorbed into Verizon, a RBOC. ILECs compete with competitive local exchange carriers (CLEC). When referring to the technical communities ILEC is often used just to mean a telephone provider. In Canada, the term ILEC refers to the original telephone companies such as TELUS (BC Tel and AGT), SaskTel, Manitoba Telephone Systems (MTS All stream), Bell Canada Enterprises and Aliant.
CLEC- A competitive local exchange carrier (CLEC), in the United States, is a telecommunications provider company (sometimes called a "carrier") competing with other, already established carriers (generally the incumbent local exchange carrier (ILEC)).
MSO- A multiple-system operator or multi-system operator (MSO) is an operator of multiple cable or direct-broadcast satellite television systems. A cable system in the United States, by Federal Communications Commission (FCC) definition, is a facility serving a single community or a distinct governmental entity, each with its own franchise agreement with the cable company. Though in the strictest sense any cable company that serves multiple communities is thus an MSO, the term today is usually reserved for companies that own a large number of cable systems, such as Time Warner Cable, Cablevision, Comcast, Charter Communications and Cox Communications in the United States, Rogers Communications, Videotron and Shaw Communications in Canada or Virgin Media in the UK.
ISP- an Internet service provider (ISP, also called Internet access provider) is a business or organization that offers user’s access to the Internet and related services. Many but not all ISPs are telephone companies or other telecommunication providers. They provide services such as Internet access, Internet transit, domain name registration and hosting, dial-up access, leased line access and colocation. Internet service providers may be organized in various forms, such as commercial, community-owned, non-profit, or otherwise privately owned.