Glossary

DSX1 u Cross-connection point for DS1 signals.

DTE u Data Terminal Equipment Device at the user end of a user-network interface that serves as a data source, destination, or both. DTE connects to a data network through a DCE device (for example, a modem) and typically uses clocking signals generated by the DCE. DTE includes such devices as computers, protocol translators, and multiplexers.

E1 u Wide-area digital transmission scheme used predominantly in Europe that carries data at a rate of 2.048 Mbps. E1 lines can be leased for private use from common carriers.

E3 u Wide-area digital transmission scheme used predominantly in Europe that carries data at a rate of 34.368 Mbps. E3 lines can be leased for private use from common carriers.

EEPROM u Electrically Erasable Programmable Read-Only Memory A nonvolatile PROM that can be written as well as read form. Usually used to hold information about the current system configuration, alternate boot paths, etc.

ELAN u Emulated LAN ATM network in which an Ethernet or Token Ring LAN is emulated using a client- server model. ELANs are composed of an LEC, an LES, a BUS, and an LECS. Multiple ELANs can exist simultaneously on a single ATM network. ELANs are defined by the LANE specification.

END u Enhanced Network DriverEPLD u Electrically Programmable Logic Device

ES u End System Generally, an end-user device on a network.

ESF u Extended Superframe Format Framing type used on T1 circuits that consists of 24 frames of 192 bits each, with the 193rd bit providing timing and other functions.

Ethernet u Baseband LAN specification invented by Xerox Corporation and developed jointly by Xerox, Intel, and Digital Equipment Corporation.

FCC

u

Federal Communications Commission The Government agency responsible for regulating tele-

communications in the United States.

FCC

u

Fast serial Communication Controllers Used to control the fast Ethernet port.

FDDI u Fiber Distributed Data Interface LAN standard, defined by ANSI X3T9.5, specifying a 100-Mbps token-passing network using fiber-optic cable, with transmission distances of up to 2 km. FDDI uses a dual- ring architecture to provide redundancy.

Flash u Nonvolatile storage that can be electrically erased and reprogrammed so that software images can be stored, booted, and rewritten as necessary.

Frame Relay u Industry-standard, switched data link layer protocol that handles multiple virtual circuits using HDLC encapsulation between connected devices. Frame Relay is more efficient than X.25, the protocol for which it is generally considered a replacement.

FTP u File Transfer Protocol Application protocol, part of the TCP/IP protocol stack, used for transferring files between network nodes.

GB u GigaBytes 109 bytes per second.

Gbps u Gigabits per second 109 bits per second.

HDLC u High-Level Data Link Control Bit-oriented synchronous data link layer protocol developed by ISO. Derived from SDLC, HDLC specifies a data encapsulation method on synchronous serial links using frame characters and checksums.

IMA u Inverse Multiplexing over ATM Standard protocol defined by the ATM Forum in 1997.

IMMR u Internal Memory Map Register

IP u Internet Protocol Network layer protocol in the TCP/IP stack offering a connectionless internetwork service. IP provides features for addressing, type-of-service specification, fragmentation and reassem- bly, and security.

ISDN u Integrated Services Digital Network Communication protocol, offered by telephone companies, that permits telephone networks to carry data, voice, and other source traffic.

ISO u International Organization for Standardization International organization that is responsible for a wide range of standards, including those relevant to networking. ISO developed the OSI reference model, a popular networking reference model.

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