APPENDIX I GLOSSARY

A

ATTENUATION\ Loss of communication signal energy.

B

BASEBAND\ The frequency band occupied by individual information bearing signals before they are combined with a carrier in the modulation process.

BISYNC\ Controlling of data transmission by timing signals generated at the sending and receiving stations.

BROADBAND\ Transmission facilities whose bandwidth is greater than that available on voice-grade facilities.

BUS\ Channel or path for transferring data and electrical signals.

CARRIER SENSE MULTIPLE ACCESS (CSMA)\ A protocol that controls access to a network's bus.

CARRIER SENSE MULTIPLE ACCESS WITH COLLISION AVOIDANCE (CSMA/CA)\ A protocol that requires carrier sense and in which a data station that intends to transmit sends a jam signal.

CARRIER SENSE MULTIPLE ACCESS WITH COLLISION DETECTION (CSMA/CD)\ A protocol that requires carrier sense and in which a transmitting data station that detects another signal while transmitting, stops sending, sends a jam signal, and then waits for a variable time before trying again.

CLEAR TO SEND\ A hardware signal sent from a receiver to a transmitter to indicate that the transmitter can begin sending.

CROSSTALK\ The disturbance caused in a circuit by an unwanted transfer of energy from another circuit.

F

FILTER\ A device or program that separates data, signals, or material in accordance with specified criteria.

FIREWALL\ One or more components that control the flow of network traffic between networks.

H

HANDSHAKING\ The process through which the rules for exchanging data over a communications line are defined for the two devices involved.

I

IMPEDANCE\ A measure of electrical resistance.

INTERNATIONAL STANDARDS ORGANIZATION (ISO)\ The international agency responsible for developing standards for information exchange.

INTERRUPT REQUEST LINES\ Physical connections between hardware devices and the interrupt request.

L

LINE DRIVER\ A component that includes a transmitter and a receiver.

LINK\ The communications media used to connect nodes.

M

MULTITASKING\ A mode of operation that provides for concurrent performance of two or more tasks.

N

NETWORK INTERFACE CARD (NIC)\ The expansion card that allows the workstation to communicate with the network.

AI-1

C

NETWORK OPERATING SYSTEM (NOS)\ A software package that makes it possible to implement and control a network and that enables users to make use of resources and services on that network.

NODE\ The point at the end of a branch.

NOISE\ Random electrical signals that become part of a transmission, and that serve to make the signal (information) component of the transmission more difficult to identify.

O

OPEN SYSTEMS INTERCONNECTION (OSI)\ The networking standard for interconnecting dissimilar computer systems.

P

PROTOCOL\ A formal set of conventions governing the format and control of inputs and outputs between two communicating processes.

R

READY TO SEND\ A hardware signal sent from a potential transmitter to a destination to indicate that the transmitter wishes to begin a transmission.

S

SYNCHRONOUS DATA LINK CONTROL (SDLC)\ Primary protocol supported under System Network Architecture (SNA).

SIGNAL-TO-NOISE RATIO (SNR)\ The ratio between the signal and noise levels at a given point, usually at the receiving end of the transmission.

T

TIME DOMAIN REFLECTOMETER\ A device used to test the integrity of a section of cable.

TOPOLOGY\ The physical or logical layout of a LAN.