Glossary

Distributed Function Terminal (DFT) ‹ 1) A protocol used for communication between a terminal and an IBM 3270 or IBM 3174 control unit that allows multiple concurrent logical terminal sessions. 2) A mode of operation that uses this protocol.

DLC ‹ See data link control.

DLCI ‹ See data link control identifier.

DMA (Direct Memory Access) ‹ A fast method of moving data between two subsystems without processor intervention.

DMS/DMS100 ‹ The name of a central office switch manufactured by Northern Telecom. These switches use Custom (proprietary) or National ISDN-1 (NI-1) software.

DSR, data set ready ‹ RS-232 (V.24) interface control signal, sent from the data communications equipment to the data terminal equipment on pin 6. Indicates that the DCE is connected to the telephone cir- cuit. Usually a prerequisite to the DTE issuing request-to-send. (See RS-232.)

DSU ‹ See CSU/DSU (Channel Service Unit/ Data Service Unit).

DTE (Data Terminal Equipment) ‹ Equipment serving as the data source, the data sink, or both. Refers to terminals, computer ports, and printers. Also interface signals typically presented by this equipment.

DTR (Data Terminal Ready) ‹ RS-232 (V.24) interface control signal, sent from the data terminal equipment to the data communications equipment on pin 20. Indicates the DTE is ready for data transmission and requesting connection of the DCE to the telephone circuit. (See RS-232.)

EIR ‹ Excess Information Rate

EIS ‹ The SNA Server Emulator Interface Specification.

Encapsulation ‹ Process by which an interface device places an end device’s protocol-specific frames inside a Frame Relay, X.25, or PPP frame to a frame relay network must perform encapsulation.

ETS ‹ European Telecommunications Standard from ETSI ETSI ‹ The European Telecommunications Standards Institute

EuroISDN ‹ The European implementation of Q.931, providing a common standard for ISDN signalling within Europe. Issued by ETSI under the ETS 300 series standards. Net3(BRI) and Net5(PRI). See NET (Normes Europeennes de Telecommunication).

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