A

A

Ampere

A/D CONVERSION TIME

The length of time an A/D conmverter requires to convert an analog signal into a digital value. The theoretical maximum speed is the inverse of this value.

AARP

AppleTalk Address Resolution Protocol

ABERRATION

Failure of an optical lense to produce exact point-to-point agreement between an object and its image.

ABP

Alternate Bipolar

ABSTRACT SYNTAX

A description of a data structure that is independent of machine-oriented structures and encodings.

ABSTRACT SYNTAX NOTATION ONE

(ASN.1) The OSI language for describing abstract syntax. See BER.

ACCESS CODE

In Novell LAN-based 3270 and 5250 communications products, a name with up to 15 characters used to select a host session or group of host sessions through a specified gateway server. On the server, a host session, a group of up to 5 host sessions, or a pool or such sessions or session groups is defined under the access code.

ACCESS GROUP

All stations which have identical rights to make use of a computer, network, or data PABX resources. (In LAN technology)

ACCESS METHOD

See Access Protocol.

ACCESS PROTOCOL

Also called Access Method or Access Scheme. The method of communication used between NICs on a local area network. Frames of data that contain packets of data are exchanged between NICs. See CSMA/CD, token-passing bus, and token-passing ring.

ACCESS RIGHTS

These rights list the people who can use each object in the network, and specify how each person can use the object. UNIX access rights consist of read, write, and execute permissions.

ACCESS SCHEME

See Access Protocol.

ACD

Automatic Call Distributor

ACF/NCP

See Advanced Communications Function/Network Control Program.

ACF/TCAM

See Advanced Communications Function for the Telecommunications Access Method.

ACF/VTAM

See Advanced Communications Function for the Virtual Telecommunications Access Method.

ACID

Ansi Creators in Demand

ACK

See Acknowledge

ACKNOWLEDGE

(ACK) A character or sequence of characters sent by a receiver to notify a sender the last message was received correctly.

ACL

Access Control List

ACROMAT

Lense consisting of two or more elements that has been corrected for chromatic aberration at two selected wavelengths.

ACS

Asynchronous Communication Server

ACSE

See Association Control Service Element.

ACTIONMEDIA® BOARD

Intel I750®-based board set that performs realtime compression and full-screen playback.

ACTIVE HUB

See Hub.

ACTIVE OBJECT

The object that is displayed front most on the desktop, or would appear front most if the application was made visible.

ACTIVE PIXEL REGION

On a computer display, the area of the screen used for actual display of pixel information.

ACTLU

Activate Logical Unit

ACTPU

Activate Physical Unit

AD

IC part number prefix indicating Analog Devices.

AD HOC CONFERENCING

A dynamic environment in which two or more LAN Distance workstations dial in to a common LAN Distance workstation (the hub) and conference with each other across the virtual LAN connections. See also Hub.

ADAPTER

The hardware that connects the computer bus to the 68-pin PC Card sockets in the PCMCIA slot. OR See LAN Adapter.

ADAPTER SEGMENT

A name sometimes used for the upper memory area, at hexadecimal addresses A000 through EFFF (640K to 1024K).

ADAPTIVE COMPRESSION

Data compression software that continually analyzes and compensates its algorithm, depending on the type and content of the data and the storage medium.

ADAPTIVE DIFFERENTIAL PULSE CODE MODULATION

An encoding format for storing audio information in a digital format.

ADC

National Semiconductor part prefix that indicates the device is in device family: Data Conversion

ADDITIVE COLOR

Color produced by "adding" colors, usually the combination of red, green and blue.

ADDRESS

An identifier for a physical or logical device on a network. In SNA networks, each physical unit, logical unit, and system service control point has an address. In local area networks, each node on the network has an address.

ADDRESS CLASS

A classification of network Internet Protocol addresses. The three main classes are A, B, and C. The classes are separated according to the number of hosts attached to each network. Each Internet Protocol address consists of a network portion (netid) and a host portion (hostid). An Internet Protocol address identifies a network to which a host is attached and specifies the specific host attached to the network.

ADDRESS MASK

A bit mask used to select bits from an Internet address for subnet addressing. The mask is 32 bits long and selects the network portion of the Internet address and one or more bits of the local portion. Sometimes called subnet mask.

ADDRESS RESOLUTION

A means for mapping Network Layer addresses onto media-specific addresses. See ARP.

ADDRESS RESOLUTION PROTOCOL

(ARP) The Internet Protocol that dynamically identifies a high-level Internet address based on a known low-level physical hardware address. ARP broadcasts across a single physical network, but only on networks that support hardware broadcasts. ARP dynamically binds a high level internet address to a low level physical hardware address.

ADJACENCY

In OSPF, adjacency is created between neighboring routers for the purpose of exchanging routing information. In OSI, adjacency refers to a directly connected ES or IS that was configured or learned through the ES-IS protocol. See OSPF, OSI, ES, IS, and ES-IS.

ADLC

See Asynchronous Data Link Control

ADMD

See Administration Management Domain.

ADMINISTRATION MANAGEMENT DOMAIN

(ADMD) An X.400 Message Handling System public service carrier. Examples: MCImail and ATTmail in the U.S., British Telecom Gold400mail in the U.K. The ADMDs in all countries worldwide together provide the X.400 backbone. See PRMD.

ADP

Automatic data processing

ADPCM

See Adaptive Differential Pulse Code Modulation.

ADSP

AppleTalk Data Stream Protocol

ADU

Asynchronous data unit

ADVANCE

Advanced Driver and Vehicle Advisor Navigation Concept

ADVANCE COMMAND PROCESSING

An option for the single Ethernet interface card in which a chip links commands to expedite command transmission.

ADVANCED COMMUNICATIONS FUNCTION FOR THE TELECOMMUNICA-TIONS ACCESS METHOD

(ACF/TCAM) Host communications access method which provides similar functions to those provided by ACF/VTAM, plus some data queuing functions not provided by either ACF/VTAM or ACF/VTAME.

ADVANCED COMMUNICATIONS FUNCTION FOR THE VIRTUAL TELECOM-MUNICATIONS ACCESS METHOD

(ACF/VTAM) System program which runs on an IBM host computers and controls communication between host application or service programs and terminals. The prefix ACF distinguishes contemporary VTAM releases from earlier ones which provided much less comprehensive support.

ADVANCED COMMUNICATIONS FUNCTION/NETWORK CONTROL PROGRAM

(ACF/NCP) Software resident in an IBM 37x5 communications controller that manages communication between the host system attached to the controller and other devices on the network (usually, but not necessarily an SNA network).

ADVANCED NETWORK DRIVER INTERFACE SPECIFICATION

(ANDIS) An upgraded version of the Network Driver Interface Specification (NDIS). It is the interface between the LAN Distance logical adapter and the WAN adapter MAC.

ADVANCED PEER-TO-PEER NETWORKING

(APPN) An implementation of the Systems Network Architecture (SNA) LU 6.2 protocol that allows interconnected systems to communicate and share the processing of programs. APPN conforms to the IEEE 802.2 interface. Applications using it are supported by the LAN Distance product.

ADVANCED POWER MANAGEMENT

(APM) This enables Windows to extend battery life, display power-status information, and work together with the suspend features of battery-powered personal computers.

ADVANCED PROGRAM-TO-PROGRAM COMM-UNICATION

(APPC) An IBM protocol for developing peer-to-peer communications that allows programs to communicate with equal control. APPC is implemented through SNA Logical Unit Type 6.2.

ADVANCED RESEARCH PROJECTS AGENCY

Developed the first major packet-switched network; operates within the U.S. Department of Defense.

ADVANCED RESEARCH PROJECTS AGENCY NETWORK

(ARPANET) A packet switched network developed in the early 1970s. The "grandfather" of today's Internet. ARPANET was decommissioned in June 1990.

AEP

AppleTalk Echo Protocol

AF

National Semiconductor part prefix that indicates the device is in device family: Active Filter

AFI

See Authority and Format Identifier.

AFP

AppleTalk Filing Protocol

AFRP

ARCNET Fragmentation Protocol

AGENT

In the client-server model, the part of the system that performs information preparation and exchange on behalf of a client or server application. See NMS, DUA, MTA.

AGGREGATE INPUT RATE

The sum of all data rates of the terminals or computer ports connected to a multiplexor or concentrator; burst aggregate input rate refers to the instantaneous maximum.

AGS

Asynchronous Gateway Server

AH

National Semiconductor part prefix that indicates the device is in device family: Analog Switch (Hybrid)

AI

Artificial Intelligence

AIAG

Automotive Industry Action Group

AIM

Automatic Identification Manufacturers.

ALERT

A message sent to a system services control point to report that an error occurred that requires operator intervention or attention. For the LAN Distance product, alerts for communications errors are generated through FFST/2. FFST/2 can be configured to forward the alerts to NetView or central LAN management point.

ALGORITHM

A step-by-step procedure for solving a problem or accomplishing some end. In compression software it refers to a specific formula used to compress or decompress video.

ALIASING

A form of image distortion associated with signal sampling. A common form of aliasing is a stair-stepped appearance along diagonal and curved lines.

ALL NEW

Parts not interchangeable with the previous design.

ALPHANUMERIC

The character set containing letters, numbers, punctuation marks, and symbols.

ALRU

Automatic Line Record Update

ALTERNATE VOICE DATA

Telephone lines which have been electronically treated to handle both voice and data signals. Typically leased on overseas circuits to save space.

AM

National Semiconductor part prefix that indicates the device is in device family: Analog Switch (Monolithic)

AM

Active Monitor

AMERICAN BELL STANDARD

See Bell 103 and 212A.

AMERICAN MEGATRENDS, INC.

BIOS manufacturer for PCs.

AMERICAN NATIONAL STANDARDS INSTITUTE

(ANSI) A standards-setting, non-government organization which develops and publishes standards for voluntary use in the United States.

AMI

See American Megatrends, Inc. OR Alternate Mark Inversion

AMPS

Advanced Mobile Phone System

AN

Associated Number

ANAC

Number that plays back the number of the telephone that called it. ANAC numbers are convenient if you want to know the telephone number of a pair of wires.

ANALOG

An electrical circuit that is represented by means of continuous, variable physical quantities (such as voltages and frequencies), as opposed to discrete representations (like the 0/1, off/on representation of digital circuits). Analog data communications are used to send data over normal voice telephone lines at actual transmission rates of up to 19.2 kbps. Data compression potentially can increase throughput up to four times this rate. In all practicality, throughput rates do not normally exceed 38.8 kbps when using analog data transmission (V.42bis standard). Modems are used to transmit binary analog data. See also Digital.

ANALOG VIDEO

A video signal that represents an infinite number of smooth gradations between given video levels. By contrast, a digital video signal assigns a finite set of levels. See also Digital Video.

ANAMORPHIC

Unequally scaled in vertical and horizontal dimensions.

ANDIS

See Advanced Network Driver Interface Specification .

ANGSTROM

Unit of measure for the wavelength of light (10A = 1nm).

ANI

Automatic Number Identification

ANNULAR RING

An 8mm (5/16") wide black band printed at 2.5m (8.2') intervals on standard Ethernet coaxial cable to identify locations at which transceivers may be connected.

ANONYMOUS REMAILER

A system on the Internet that allows you to send e-mail anonymously or post messages to Usenet anonymously. You apply for an anonymous ID at the remailer site. Then, when you send a message to the remailer, it sends it out from your anonymous ID at the remailer. No one reading the post will know your real account name or host name. If someone sends a message to your anonymous ID, it will be forwarded to your real account by the remailer.

ANSI

See American National Standards Institute.

ANSWER

To acknowledge an attempt from a remote workstation to establish a LAN Distance connection. Answering a call does not imply a successful connection. The dialing and answering workstations must negotiate to establish the connection.

ANSWER CRITERIA

The set of specifications that enables a particular Answer Mode.

ANSWER MODE

Used when expecting a call from another computer. The modem uses "originate mode" when calling another computer. Some modems operate only in originate mode. To communicate with these modems, switch to answer mode after placing (originating) a call.

ANTI-TEL

On the 400th system boot, displays the message "VIRUS ANTITELEFONICA (BARCELONA)" and overwrites the first two hard disks with random data.

ANTIALIASING

A form of interpolation used when combining images; pixels along the transitions between images are averaged to provide a smooth transition.

AOW

See Asia and Oceania Workshop.

API

See Applications Programming Interface.

APL

A Programming Language - A general purpose programming language for diverse applications.

APM

See Advanced Power Management

APPC

See Advanced Program-to-Program Communications.

APPLETALK

Networking protocols and networking software proprietary to Apple Computers. A communications protocol developed by Apple Computer to allow networking between Macintoshes. All Mac computers have a LocalTalk port, running AppleTalk over a 230k bit serial line. AppleTalk also runs over Ethernet (EtherTalk) and Token Ring (TokenTalk) network media. See OSI Model.

APPLICATION

Software such as a word processor or spreadsheet that you use to perform a specific type of work.

APPLICATION LAYER

The seventh layer of the ISO OSI model. This layer passes requests and responses between the network and applications. The top-most layer in the OSI Reference Model providing such communication services as electronic mail and file transfer.

APPLICATION PROFILE

A set of instructions, contained in a file with the extension .NIA, for installing an application program on a server. Each application program installed can have its own profile (IBM PC LAN)

APPLICATION PROGRAM INTERFACE

See Applications Programming Interface

APPLICATION SERVICES

Those services referred to by the upper three layers of the OSI reference model.

APPLICATIONS PROGRAMMING INTERFACE

A set of routines that an application program uses to request and carry out lower-level services performed by the computer's operating system. For Windows, the API also helps applications manage windows, menus,icons, and other GUI elements. For a local area network, an API provides applica tions with routines for requesting services from lower levels of the network. In networks built on the ISO OSI model, APIs usually work on the seventh layer. Loosely used to describe the point at which software modules or layers meet and interconnect. The API specifies the access methods a programmer can use to exercise functionality provided by a kernel or library. An example of an API is the "C" language interface used to access CSTA capabilities supported by the Telephony Server. See TAPI, MAPI.

APPN

See Advanced Peer-to-Peer Networking (APPN).

ARCHIE

A protocol to simplify the task of finding files on the internet by building an index of files during non-peak hours and then letting you search the index, returning lists of sites whose files match keywords you provide. Commands can be issued to an Archie server directly, or through the use of Archie client software.

ARCHIVED FILE

A file that has been archived using either LZEXE or PKLITE, file compression utilities.

ARCNET

See Attached Resource Computer Network.

ARE

All Routes Explorer

ARE ADDRESS

In OSI, the remainder of the NSAP address that does not contain the system ID or the selector.

AREA

In OSI, a routing subdomain that maintains detailed routing information about its own internal composition, while also maintaining routing information that allows it to reach other routing subdomains. An area corresponds to a level 1 subdomain.

AREA DIODE ARRAY

Rows and collumns of light-aensitive semiconductors within a camers. Sometimes referred to as a matrix array or focal plane array; used in most television cameras.

ARGUS

ARGUS Protocol

ARI

Address Recognized Indicator Bit

ARO

See Automatic request for retransmission.

ARP

See Address Resolution Protocol.

ARPA

See Advanced Research Projects Agency

ARPANET

See Advanced Research Projects Agency Network

ARSB

Automated Repair Service Bureau

ARTIC

A WAN adapter that provides asynchronous and synchronous transmission support for up to 8 communication ports.

ARTICLE

A message written by a Usenet News user and posted to the network. Articles are similar to electronic mail messages, but are not private. They are intended to be seen by potentially hundreds of thousands of people. Also called "postings".

ARTICLE NUMBER

(USENETNews) For each article in a group, an article number is shown. This is the number used by your news server to track the article. This number is local to your news server only, and is number is not a meaningful identifier outside of your news server. If you need a globally (internet-wide) unique identifer for an article, use its message ID.

ARTIFACT

An unintended, unwanted visual aberration in a video image.

ARTIFICIAL INTELLIGENCE

A theory that a computer can effectively mimic human intelligence and develope its own identity and awareness. Why anyone would want to build a computer that would demand overtime pay is unknown.

AS

See Autonomous System.

AS/400

IBM mainframe computer that can act as a host for a Token-Ring gateway connection.

ASCII

ASCII stands for "American Standard Code for Information Interchange." This is a standard method of encoding characters that enables text generated by one program or computer to be understood by another program or computer. A code for representing characters to a processor; each character is represented by 7 bits with an optional eighth bit for parity checking. ASCII is used on microcomputers; EBCDIC is used on IBM host computers.

ASI

Adapter Support Interface

ASIA AND OCEANIA WORKSHOP

(AOW) One of the three regional OSI Implementors Workshops, equivalent to OIW and EWOS.

ASN.1

See Abstract Syntax Notation One.

ASP

AppleTalk Session Protocol

ASPECT RATIO

Ratio of width to height for the frame of the televised picture. The U.S. standard is 4.3. Also the value obtained when the larger dimension is divided by the smaller dimension. For example, a part measuring 9" by 5" has an aspect ration of 1.8. When an image is displayed on different screens, the aspect ratio must be kept the same to avoid "stretching" in either the vertical or horizontal direction. For VGA and Indeo™ video technology, the aspect ratio is 4:3 yielding 160X120, 320X240 and 640X480 sizes.

ASSOCIATION CONTROL SERVICE ELEMENT

(ACSE) The method used in OSI for establishing a call between two applications. Checks the identities and contexts of the application entities, and could apply an authentication security check.

ASYMMETRICAL COMPRESSION

A system which requires more processing capability to compress an image than to decompress an image. It is typically used for the mass distribution of programs on media such as CD-ROM, where significant expense can be incurred for the production and compression of the program but the playback system must be low in cost.

ASYNCHRONOUS

In asynchronous communications, each byte is framed with a start and a stop bit for alignment. The characters can use seven or eight bits and may use the eighth bit for a parity check. Asynchronous communications are generally analog and are relegated to use for dial-in and dial-out services. Asynchronous communications normally are not used in transmissions of more than 9.6 kbps. At higher rates, modems usually switch to synchronous transmission-regardless of what is sent by your communications software.

ASYNCHRONOUS COMM-UNICATION

Communication between computers at irregular intervals. To handle this kind of communication, the modem adds start and stop bits to each character it sends. The start bit lets the receiving computer know when a new character has started. The stop bit indicates the end of the character.

ASYNCHRONOUS DATA LINK CONTROL

(ADLC) A communications protocol which can be used to connect a PC to a gateway. Generally used for remote communications, it is also possible to use ADLC with a direct link to the gateway PC.

ASYNCHRONOUS TIME-DIVISION MULTIPLEXING

A TDM that multiplexes asynchronous signals by oversampling; also infrequently used to mean concentrator.

ASYNCHRONOUS TRANSFER MODE

(ATM) ATM is one of the newest WAN protocols that promises future gigabit-per-second data throughput rates. ATM currently is being developed as a LAN access protocol at bandwidths of 100 mbps and 143 mbps to compete with FDDI. One advantage of ATM is the promise of merging LAN and WAN access protocols into one single standard, which will alleviate the need for encapsulation into another frame or packet in bridges and routers. A connection-type transmission mode carrying information organized into blocks (header plus information field); it is asynchronous in the sense that recurrence of blocks depends on the required or instantaneous bit rate. Statistical and deterministic values have been proposed that correspond respectively to the packet and circuit values defined for information transfer mode. ATM provides a flexible and fast packet-switching service on top of SONET. The packets are called cells and are 48 bytes in size. These cells are the fundamental units for data transport. Data traffic from multiple channels are multiplexed at the cell level. ATM can support a broad spectrum of traffic types, including LAN traffic. In the case of LAN traffic, the longer packet sizes are broken down to small cells by LAN Terminal Adapters that im-plement the Adaptation Layer. The packet switch services provided by ATM also can be used by other transport services, such as Frame Relay. The cell multiplexing in ATM provides better bandwidth utilization. Cells are allocated on demand during times of high traffic, which is typical of many LAN applications. If there is no traffic to send, no new cells are generated. Cell size has been the subject of much controversy. The voice people wanted small cell sizes of 32 bytes to increase the likelihood of cells being available when they are needed on short notice. The data people felt that small cells introduced greater overhead in packet splitting and recombination because data packet sizes in LAN applications tend to be large. They were willing to settle for a cell size of 64 bytes. A compromise of 48 bytes-per-cell was adopted by both factions. Each cell is preceded by a five-byte header, making the total cell size 53 bytes. The header contains the cell destination. Before two ATM nodes exchange cells, they go through a call establishment phase in which a virtual circuit identifier is assigned. This virtual circuit identifier must be used in the data transfer phase. Each data cell contains this virtual circuit identifier. ATM nodes can generate a mixture of data traffic types such as voice, data, and video. The cells that contain this data traffic are multiplexed across the same physical link between two ATM nodes. To identify this common physical link, an identifier called a virtual path identifier is included in each cell. An ATM switch can use the virtual circuit identifier and the virtual path identifier to determine where the cell should go. Some vendors are considering using ATM to provide the media access control mechanism for LANs.

AT COMMAND SET

The set of industry-standard commands used to control the modem. Each command line must start with the two-character attention code AT (or at). See Attention Code.

ATDM

See Asynchronous Time-Division Multiplexing

ATE

Automatic test equipment

ATH

Abbreviated Trouble History

ATIS

Advanced Traveler Information System

ATM

See Asynchronous Transfer Mode

ATMS

Advanced Traffic Management System

ATP

AppleTalk Transaction Protocol

ATTACHED RESOURCE COMPUTER NETWORK

(ARCnet) ARCnet is a trademark of Datapoint, Inc., and is proprietary, although widely licensed and used under various brand names. Standard Microsystems Corp. and Thomas-Conrad Corp. are the leading purveyors of ARCnet products, although many other ARCnet products are produced using SMC ARCnet chips. ARCnet, which was originated at DataPoint Corporation by John Murphy, predates the token-passing standards of the IEEE 802 committee. ARCnet originally ran over RG62 coaxial cable, but now also supports twisted- pair, fiber optic, and infrared media. The current implementation of ARCnet offers a 2.5Mb/s transmission speed. To improve upon current performance, however, a 20Mb/s ARCnet standard is under development. ARCnet is an efficient token-passing network with a distributed star or "unrooted" tree topology. When an ARCnet node sends a message, all of the other nodes receive the message at about the same time. All nodes, except the destination node, ignore the message, as ARCnet passes the token based upon node address. The mechanics of interpreting the token are all taken care of by the MAC level hardware on the ARCnet controller (the COM 9026 in most cases). The ARCnet protocol uses positive acknowledgments of message receipt and generally has a maximum packet length of 512 bytes. Some vendors provide software drivers that increase the 512 byte message packet size to 4K bytes, thus significantly improving the transmission throughput. The first two bytes are for the source and destination address. The next two bytes indicate the packet data length. The remaining 508 bytes contain the message. Although ARCnet defines up to 256 different node addresses, only 255 are usable because address 0 is reserved for broadcasts to all stations. The remaining 508 bytes contain the message. Each node is offered the token in station number sequence. When a node receives the token, it can transmit a message. The ARCnet protocol specifies a limit of one packet per transmission. Once that transmission is completed and either a positive acknowledgment has been received, or if the node does not need the token, the token is passed on to the next node, as determined by the node's address. If more than one message needs to be transmitted, the sending node must wait until the token has gone around the network again. In the unlikely event that an extra token is generated, it cannot survive very long because of the manner in which the ARCnet protocol works. Basically, communications from two different nodes will interfere with each other and the end result will be that both tokens would get lost. If a token is lost, the entire LAN assumes an idle state. Each node continually monitors activity on the LAN. If no activity is detected for 78.2+s (microseconds), a reconfigure timer is started. The programmed time is based on each node's address. If node addresses are unique, as they are supposed to be, one node will time-out before all of the others. This node then becomes responsible for initiating a new token. The network reconfigures itself and communication resumes. As this feature illustrates, ARCnet's real elegance is in its simplicity, as compared to the IEEE's 802.4 and 802.5 standards. The ARCnet protocol can be described as isochronous, because each byte is preceded by a start interval and ended with a stop interval. Unlike asynchronous protocols, there is a constant amount of time separating each data byte. Each byte always consumes eleven clock intervals, with a single clock interval being 400ns (for 2.5Mb/s ARCnet). As a result, one byte is transmitted every 4.4+s. The ARCnet medium, or line, idles in a logic 0 condition. A logic 0 or "space" is defined as no line activity, and a logic 1 or "mark" is defined as a pulse of 200ns. All transmissions start with an Alert Burst, consisting of six-unit intervals of mark. Eight-bit data characters are then sent, with each character preceded by two-unit intervals of mark and one unit of space. There are five types of transmissions- Invitations to Transmit, Free Buffer Enquiries, Data Packets, Acknowledgments, and Negative Acknowledgments

ATTACHMENT UNIT INTERFACE

(AUI) The interface between the Ethernet/IEEE 802.3 controller and the base-band transceiver or broadband modem. An IEEE term for a connector that connects an external transceiver to the AUI plug on an Ethernet NIC. A 15 pin shielde, twisted pair Ethernet cable used (optionally) to connect between network devices and a MAU. (Also see DIX connector.)

ATTENTION CODE

The two-character sequence AT or at. Signals the modem that one or more modem commands are to follow. See AT Command Set.

ATTENUATION

The reduction in the amplitude of a transmitted signal. Due to attenuation many listening devices, such as LAN NIC adapters, may confuse incoming signals with noise, if the signals can be detected at all. The listening device can lower its threshold for signals qualifying as 1s. This could lead to errors, since it is easier for noise pulses to register as actual transmission. Therefore, the smaller the amount of attenuation of the signal, the more acceptable it becomes.

ATTRIBUTE

A characteristic or property; for example, the color of a line, the length of a data field, or a typeface characteristic such as size. The form of information items provided by the X.500 Directory Service. The directory information base consists of entries, each containing one or more attributes. Each attribute consists of a type identifier together with one or more values. Each directory Read operation can retrieve some or all attributes from a designated entry.

AUDIO

Sound for multimedia systems. Audible range is typically from 20Hz to 20,000Hz (20KHz).

AUDIO VIDEO INTERLEAVED

File format for digital video and audio under Windows. File format is cross-platform compatible, allowing AVI video files to be played under other operating systems.

AUDIO VIDEO KERNEL

DVI system software designed to play motion video and audio across hardware and operating system environments.

AUDIO-VIDEO SUPPORT SYSTEM

DVI system software for DOS. It plays motion video and audio.

AUDIT LOG

A record of all LAN Distance connection attempts, successful LAN Distance connection activity, link statistics, and security events at a LAN Distance Remote workstation or LAN Distance Connection Server workstation.

AUI

See Attachment Unit Interface.

AUTH

Authentication Service

AUTHORING SYSTEM

Software which helps developers design interactive courseware easily, without the painstaking detail of computer programming.

AUTHORITY AND FORMAT IDENTIFIER

Part of the OSI NSAP address that specifies the format of the IDI.

AUTO ANSWER

See Automatic Answering.

AUTO-RELIABLE MODE

The modem automatically negotiates with the remote modem for a connection, determines whether or not it can use error control and data compression during a transmission, and determines which error control and data compression protocol it can use.

AUTOBAUD

Automatic determination and matching of transmission speed.

AUTOMATIC ANSWERING

The modem automatically answers the phone after a certain number of rings. This is in contrast to manual answering, where a person sends an AT command to the modem to cause the modem to answer a ringing telephone.

AUTOMATIC DIALING

The modem automatically dials the telephone. This is in contrast to manual dialing, where a person dials the number.

AUTOMATIC REQUEST FOR RETRANSMISSION

An error control method in which the receiving device informs the transmitting device which transmission blocks were received successfully; the transmitting device retransmits any block not successfully received.

AUTONOMOUS NETWORK

See Autonomous System.

AUTONOMOUS SYSTEM

Also called Autonomous Network. A collection of routers and networks that fall under one administrative authority and cooperate closely to propagate netwoInternet (TCP/IP) terminology for a collection of gateways (routers) that fall under one administrative entity and cooperate using a common Interior Gateway Protocol (IGP). See subnetwork.rk reachability (and routing) among themselves using an interior gateway protocol of their choice.

AVD

See Alternate Voice Data.

AVI

Automatic Vehicle Identification

AVI

See Audio Video Interleaved.

AVK

See Audio Video Kernel.

AVL

Automatic Vehicle Location

AVSS

See Audio-Video Support System.

AWGN

Additive White Gaussian Noise

AWK

Pattern scanning and processing language

AXE

(Another X Editor) This X editor (aXe) is based on the Athena toolkit.

AZUSA

Every 32 times an infected computer is booted, disables the LPT1 and COM1 ports until the computer is rebooted.