A

AAC Augmentative and Alternative Communication. Any communication which supplements or augments speech, including words, sign systems and written sysmbols. The user indicates the symbols needed from a book, chart or electronic aid. It attempts to provide those with severe expressive disorders with an efficient communication system.

AAL ATM Adaption Layer

AAL 3/4 An AAL enables connection-oriented transfer of connectionless data, i.e., SMDS.

AAL5 A low-overhead AAL tailored for data, such as Frame Relay and multiprotocol LAN packets.

ABM (Asynchronous Balanced Mode) A communication mode used in HDLC that allows either of two workstations in a peer-oriented point-to-point configuration to initiate a data transfer.

ABR Area Border Routers

ABR Available bit rate

Access Method Generally, the method by which networked stations determine when they can transmit data on a shared transmission medium. Also, the software within an SNA processor that controls the flow of information through a network.

ACS Access Control System

Access SecuritySystem Remote access security software that works with network-based security servers.

Active Hub A multiport device that amplifies LAN transmission signals.

Adapter A board installed in a computer system, usually a PC, to provide network communication capabilities to and from that computer system. Also called a network interface card (NIC).

ADN Advanced Digital Network.

ADRI Advanced Distributed Recovery Intelligence

AFP (AppleTalk* Filing Protocol) Protocol that lets workstations access files from remote file servers. The protocol corresponds to layer 6 of the Open Systems Interconnection (OSI) reference model. See OSI.

Agent Software that receives queries and returns replies on behalf of an application. In network management systems, agents reside in all managed devices and report the values of specified variables to management stations.

AIW APPN Implementors Workshop

AL Attention Line

AMP Adapter Management Protocol

ANSI American National Standards Institute

API (Application Program Interface) Means of communication between programs to give one program transparent access to another. APIs serve various computing purposes. In networking, for example, an API offers software applications (such as a database manager) transparent access to OS/2* files,devices or interprocess communications.

APPC (Advanced Program-to-Program Communications) Implementation of SNATM LU 6.2 sessions that permits personal computers in an SNA network to communicate in real time with the mainframe host and other networks.

Applet A small Java programthat maybe used on a Web page.

AppleTalk An Apple* networking system that operates over STP wire at 230 Kbps.

Application layer Layer 7 of the OSI Reference Model; implemented by various network applications, including electronic mail, file transfer and terminal emulation.

APPN (Advanced Peer-to-Peer) NetworkinSNA facility that provides distributed processing based on Type 2.1 network nodes and LU 6.2.

APPN-NN Advanced Peer-to-Peer NetworkingNetwork Node

ARAP AppleTalk Remote Access Protocol

ARB Adaptor Request Blocks

Archie A network service that searches FTP sites for files.

ARP (Address Resolution Protocol) Internet protocol for dynamically mapping Internet addresses to physical hardware addresses on LANs. Limited to LANs that support hardware broadcast.

ARPANET Advanced Research Projects Agency Network - a system developed by ARPANET in the 1960's as the first resilient large-scale packet switched network. A precursor to the Internet, it was in use between 1971 and 1990 when it was officially dismantled.

ASBR Autonomous System Boundary Router

ASCII American Standard Code for Information Interchange

ASIC Application-Specific Integrated Circuit

Async (Asynchronous) A form of communication in which data is sent using start and stop bits, without regard for the time needed for transmission.Compare to synchronous transmission.

Async-Sync PPP Conversion: Method by which PPP data sent between a computers COM port and the ISDN is converted by the terminaladapter to/from asynchronous to synchronous traffic.

AT (Asynchronous Transmission) Data transmission one character at a time, with intervals of varying lengths between transmittals. Start and stop bits at the beginning and end of each character control the transmission.

ATM (Asynchronous Transfer Mode) A packet switching technique which uses packets, or cells, of fixed length to transmit multiple types of information (voice, video, data). Speeds vary from the 1.5 Mpbs to 622 Mbps and above. Also referred to as BISDN.

ATM Forum An industry alliance of more than 500 companies dedicated to rapidly standardizing ATM through design and specification work.

ATM Layer The part of the BISDN protocol stack that handles most of the ATM routing and processing.

ATM Switch A hardware device that takes an incoming ATM cell and directs it to one or more of many potential output interfaces.

Attenuation The decrease in magnitude of the power of a signal transmitted over a wire, measured in decibels. As attenuation increases, signalpower decreases.

AU Access Unit

AUI (Attachment Unit Interface) Cable An IEEE 802.3 cable connecting the MAU (Media Access Unit) to a networked device; AUI also may refer to the host backpanel connector to which an AUI cable attaches.

Autonomous System (AS) In Internet (TCP/IP) terminology, a series of gateways or routers that fall under a single administrative entity and cooperate using the same Interior Gateway Protocol (IGP).

AUI Attachment Unit Interface

Auto-partitioning A function of all repeaters, whereby a faulty segment is automatically isolated to prevent the fault affecting the entire network. The segment is automatically reconnected by the repeater when the fault condition is rectified.