ABR--available bit rate.
ADSL--asymmetric digital subscriber line. Available through several telecommunications carriers to accommodate the need for increased bandwidth for Internet access and telecommuting applications.
ATM --Asynchronous Transfer Mode. International standard for cell relay in which multiple service types (such as voice, video, or data) are conveyed in fixed-length (53-byte) cells. Fixed-length cells allow cell processing to occur in hardware, thereby reducing transit delays. ATM is designed to take advantage of high-speed transmission media such as E3, SONET, and T3.
CO--central office. Local exchange (local switch) that terminates individual local telephone subscriber lines for switching, and connects to the public network. A CO is known as a class 5 switch office. For example, 5ESS by Lucent and DMS 100 by Nortel.
CPE--customer premise equipment. Devices such as channel service units (CSUs)/data service units (DSUs), modems, and ISDN terminal adapters, required to provide an electromagnetic termination for wide-area network circuits before connecting to the router or access server. This equipment was historically provided by the telephone company, but is now typically provided by the customer in North American markets.
DSL--digital subscriber line available through several telecommunications carriers to accommodate the need for increased bandwidth for Internet access and telecommuting applications.
FXO--foreign exchange office. An FXO interface connects to a central office.
FXS--foreign exchange station. An FXS interface connects directly to a standard telephone, supplying ring voltage, dial tone, and so on.
G.SHDSL--Multirate Symmetrical High-Speed Digital Subscriber Line
IAD--integrated access device. A CPE device used to combine services from various sources onto a common platform for transmission on a common transport span. Typically, an IAD combines various voice and data services such as circuit-based services like traditional POTS and packet-switched services such as frame relay or ATM.
PVC--permanent virtual circuit.