instant messaging use twisted-pair cabling rather than more The ability to exchange e-mail in near-real expensive, harder-to-install and move coaxial time without typing in an address. Users cabling. Hubs are sometimes referred to as merely click an icon representing the user to concentrators. whom the message is intended, type a mes- sage, and then click Submit (or press the HTTP (HyperText Transfer Protocol) Return key) to send the message. The protocol used to link Internet sites to one another. For example, HTTP provides links intermodal competition to servers containing text, graphical images, Competition between services based on dif- and videos. ferent media and technology. For example, mobile services compete with wireline ser- ILECs (Incumbent Local Exchange vices for local and long-distance calling. Carriers) Cable TV companies compete with telephone The former Bell and independent telephone companies such as AT&T and CenturyLink. companies that sell local telephone service. This term differentiates incumbent telephone Internet companies that were the providers of tele- The Internet-with a capital I-is an entity phone service prior to 1996 from competitors composed of multiple worldwide networks, such as Paetec, XO Communications, and tw tied together by a common protocol, TCP/IP. telecom. intranet IMS (Internet Protocol Multimedia The use of web technologies for internal Subsystem) operations. Intranets are used by organiza- Enables applications for voice, video, and tions as a way to make corporate informa- online games to be stored, billed for, and tion and applications readily accessible by Glossary employees. An example is a corporate tele- and dial-up telephone lines. ISPs often own phone directory that can be accessed by a Internet backbone networks. ISPs supply ser- browser. vices such as voicemail, hosting, and domain name registration. inverse multiplexer Instead of combining individual channels IXCs (Interexchange Carriers) into one "fat" pipe, which is what a multi- The long-distance compani