B

B CHANNEL

A "bearer" channel is a fundamental component of ISDN interfaces. It carries 64 Kbps in either direction, is circuit switched, and can carry either voice or data. See also BASIC RATE INTERFACE (BRI) and ISDN.

B8ZS

See Binary Eight Zero Suppression.

BACK DOOR

See Trap Door

BACK END

An application that provides information or services to other applications. Used in conjunction with the term Front End.

BACKBONE

1. In packet switched networks, the major transmission path for a PDN. 2. The trunk media of a multimedia LAN separated into sections by bridges, gateways or routers. 3. PDS terminology for that part of the distribution system, including both wire and fiber cables, which is often called riser or house distribution. The backbone does not include the interconnection cables which connect ISN equipment such as Packet Controllers and Concentrators, to cross-connects or interconnects. The primary connectivity mechanism of a hierarchical distributed system. All systems which have connectivity to an intermediate system on the backbone are assured of connectivity to each other. This does not prevent systems from setting up private arrangements with each other to bypass the backbone for reasons of cost, performance, or security.

BACKBONE DROP

A network drop that is connected directly to the backbone segment.

BACKBONE NETWORK

In an extended LAN, the network whose primary function is to forward network datagrams between the other networks in the extended LAN.

BACKBONE SEGMENT

In a single Ethernet LAN, the Ethernet segment whose primay function is to forward datagrams between the other segments in the Ethernet. See Branch Segment

BACKFILLING

To designate memory on an expanded memory card and make it available for use as conventional memory.

BACKPLANE

A printed-circuit board, at the back of a chassis, that provides electrical interconnection between the modules inserted into the chassis. In an ISDN system, the back panel of the Concentrator and each shelf of the Packet Controller, containing circuits that carry signals among modules inserted into carrier slots.

BACKPLANE INTERFACE

A single board inside the MicroVAX Information Processor EP/EE modules and a two-board set inside the MicroVAX Information Processor module based on the Motorola 68020 Processor. The backplane interface manages communications to and from the MicroVAX processor and the Pyramid Integrator backplane.

BACKWARD EXPLICIT CONGESTION NOTIFICATION

A frame relay method where ANSI Annex D management notifies the source device that it is receiving more frames than the frame relay backbone can process. This results in congestion at the router.

BACTERIA

Virus type where the programs make copies of themselves. Otherwise, they do nothing. Their goal is to consume all available resources on your system, such as disk space or memory. See Rabbits.

BALANCED CIRCUIT

A circuit whose two sides are electrically alike and symmetrical to a common reference point, usually ground.

BALL GRID ARRAY

(BGA) Integrated circuit package which has the leads - solder bumps configured in an array - on the bottom instead of on the perimeter. A leadless package that is not susceptible to bent or skewed leads and thus can be easily handled.

BALUN

A device that converts the impedance of one interface to the impedance of a second interface. Short for "balance/unbalance," a balun (pronounced "bay lun") allows twisted pair cable to be used with NICs intended for coaxial cable. Baluns provide the heterogeneous link between a coax card and a twisted pair cable on LANs operating at 4Mb/s or slower. Often, a mixture of baluns from a variety of manufacturers can become the Achilles' heel of the LAN, without the installer having any idea that the mixture is the problem. The function of the balun is also being integrated into some NIC adapters and active hubs.

BANDWIDTH

Usually used in context to refer to the amount of data/unit of time that must move from one point to another, such as from CD-ROM to processor.

BANK SWITCHING

A technique for sequentially reading page frames in expanded memory. The 64K page frames are brought into the upper memory block from an expanded memory card, then read and swapped back to the card so that the next 64K page frame can be brought in.

BAPI

Bridge Application Program Interface

BARREL DISTORTION

An effect that makes an image appear to bulge outward on all sides like a barrel.

BART SIMPSON (R)

Internet and OSI cult hero.

BASE ADDRESS

A memory address that serves as the starting address for programmable registers. All other addresses are located by adding to the base address.

BASE I/O PORT

Specifies a channel through which information is transferred between hardware and the CPU. Each device (card) has its own Base I/O Port setting.

BASE MEMORY

Base memory is another name for Conventional Memory. Refers to the first 640Kb of memory. DOS based programs load and run from within the first 640Kb of memory. Application programs such as Lotus 123 version 2.x or Wordperfect 5.1 must have enough conventional memory available to load and run before they can access and use any expanded memory. The expanded memory they use is mainly for data storage; the program itself does not run from expanded memory.

BASE MEMORY ADDRESS

Defines the location in the computer's memory (RAM) that the card will use. Also called RAM Start Address

BASEBAND

A signaling technique in which the signal is transmitted in its original form and not changed by modulation. Characteristic of any network technology that uses a single carrier frequency and requires all stations attached to the network to participate in every transmission. See broadband.

BASEBAND LINK

1) A communication link with only one channel, encoded by on/off switching. Examples: DH and DH+ links. 2) Contrasted with carrier-band link and broadband link.

BASEBAND SYSTEM

A data transmission system in which information is encoded, multiplexed, and transmitted without modulation of the carrier.

BASEBAND TRANSMISSION

Transmission method used for short distances (<10 miles). Uses a bandwidth whose lowest frequency is zero (DC level) transmission of raw (carrier-less) binary data. The transmission medium carries only one signal at a time.

BASIC ENCODING RULES

(BER) Standard rules for encoding data units described in ASN.1. Sometimes incorrectly lumped under the term ASN.1, which properly refers only to the abstract syntax description language, not the encoding technique.

BASIC INPUT/OUTPUT SYSTEM

Software (usually contained in ROM) that contains the coded instructions for the operating system to start the computer. Always present in PCs, a BIOS (boot ROM) is not susceptible to virus infection (unlike the boot sector on a disk). However, it is harder to update. Some computers us an EEPROM rathen than ROM, to make updating much easier. This has the unwanted effect of opening the BIOS program up to virus infection.

BASIC MEDIA ACCESS CONTROLLER

A component of the FDDI interface card that supports all MAC layer protocol services such as token claim and generation, frame transmission, reception, and stripping. The BMAC also manages the token timing logic.

BASIC RATE INTERFACE

(BRI) There are two types of interfaces in ISDN: BRI and PRI. BRI consists of two bearer or B channels and one data or D channel (2B+D). Operates at 144 Kbps. Each B channel is 64Kbps "clear" of digital bandwidth, which means that the full 64Kbps is available to your application. The B channel carries the traffic. Any network control signaling is done external to the B channel. The D channel is a 16Kbps packet switching circuit. The network control signals are transmitted over this circuit. End-user applications can also use the D channel for low-speed data-only transmissions. One BRI standard is the U interface, which uses two wires. Another BRI standard is the S/T interface, which uses four wires.

BASIC TELECOMMUNICATIONS ACCESS METHOD

An IBM software routine; the basic access method for 3270 data communication control.

BAUD

Unit of signal frequency in signals per second. Not synonymous with bits per second (bps) since signals can represent more than one bit. Baud equals bits per second only when the signal represents a single bit.

BBN-RCC-MON

BBN RCC Monitoring

BBRAM

Battery-backed RAM.

BBS

See Bulletin Board System.

BC

Block Check

BCC

See Block-Check Character.

BEARER CHANNEL

See B Channel.

BECAUSE IT'S TIME NETWORK

(BITNET) An academic computer network based originally on IBM mainframe systems interconnected via leased 9600 bps lines. BITNET has recently merged with CSNET, The Computer+Science Network (another academic computer network) to form CREN: The Corporation for Research and Educational Networking. See CSNET.

BECN

See Backward Explicit Congestion Notification.

BELL 103

(American Bell Standard) A North American standard that specifies the way modems transmit information. Version 103 applies to asynchronous modems transmitting at speeds up to 300 bps.

BELL 212A

(American Bell Standard) A North American standard that specifies the way modems transmit information. Version 212A applies to full duplex asynchronous or synchronous modems that transmit at speeds up to 1200 bps.

BELL 43401

An AT&T publication that defines requirements for data transmissionover linited-distance DC-continuous private metallic circuits supplied by the phone company.

BELL OPERATING COMPANY

(BOC) More commonly referred to as RBOC for Regional Bell Operating Company. The local telephone company in each of the seven U.S. regions.

BENCHMARK

A standard to which similar products can be tested for the purpose of comparison.

BER

See Bit error rate. OR See Basic Encoding Rules.

BERKELEY SOFTWARE DISTRIBUTION

(BSD) Term used when describing different versions of the Berkeley UNIX software, as in "4.3BSD UNIX."

BERT/BLERT

See Bit Error Rate/Block Error Rate Testing

BEZIER CURVE

A mathematical construct for describing a curve, used in CAD and illustration software to draw complex graphic shapes.

BGA

See Ball Grid Array

BIAS CURRENT

Current that flows out of an amplifier's input terminals that will produce a voltage drop across the source impedance - in a perfect amplifier this error term would be zero.

BIG-ENDIAN

A format for storage or transmission of binary data in which the most significant bit (or byte) comes first. The reverse convention is called little-endian.

BINARIES

Binary, machine readable forms of programs which have been compiled or assembled. As opposed to source language forms of programs.

BINARY DATA

Data sent over a telecommunications line is converted to the binary numbering system; each character is represented by a combination of 1s and 0s. The ASCII character set, which is represented in seven or eight bits per character, is normally used. IBM uses its own standard numbering system in mainframe communications (EBCDIC), which may require translation when the two types of systems are interfaced. Binary data is signaled by modulating amplitude, phase, or a combination of both, in nondiscreet variations.

BINARY EIGHT ZERO SUPPRESSION

(B8ZS) A method of converting eight consecutive zero bits into a recognizable, intentional bipolar violation. Converted back to eight zeros on the other end. Compatible hequipment is needed on both ends of the link.

BINARY SYNCHRONOUS COMMUNICATION

(BSC) A set of control character sequences for synchronous transmission of binary code data between stations in a data communication system. Also called "BISYNC."

BINDING

The configurable association between two layers of communications software. Two bindings are required by the LAN Distance product. First, the LAN protocol must be bound to the LAN Distance logical adapter. Second, the LAN Distance logical adapter must be bound to the WAN adapter MAC.

BIOS

See Basic Input/Output System.

BIPOLAR TRANSMISSION

Method of sending binary data in which negative and positive states alternate; used in digital transmission facilities such as DDS and T1. Sometimes called polar transmission.

BIPOLAR VIOLATION

Two or more successive pulses having the same polarity in a bit stream.

BIPOLAR WITH 8 ZERO SUBSTITUTION

See Binary Eight Zero Suppression.

BIS

The suffix "bis" designates the second version of aparticular standard.

BIS TELEPHONE

An analog multiline telephone with built-in speakerphone that is compatible with the AT&T Merlin Legend system.

BISYNC

See Binary Synchronous Communication.

BIT ERROR RATE

The ration of received bits that are in error, relative to a specific amount of bits received; usually expressed as a number referenced to a power of 10.

BIT ERROR RATE TESTER

A network diagnostic instrument used to troubleshoot LANs.

BIT ERROR RATE/BLOCK ERROR RATE TESTING

An error-checking technioque that compares a received data pattern with a known transmitted data pattern to determine transmission-line quality.

BIT SPECIFICATIONS

Number of colors or levels of gray that can be displayed at one time. Controlled by the amount of memory in the computer's graphics controller card. An 8-bit controller can display 256 colors or levels of gray; a 16-bit controller, 64,000 colors; a 24-bit controller, 16.8 million colors.

BIT-ORIENTED PROTOCOL

A protocol that moves bits across a data link without regard to the meaning of the bits.

BITMAP

A sequential collection of bits that represents, in memory, an image to be displayed on the screen. Representation of characters or graphics by individual pixels arranged in row (horizontal) and column (vertical) order. Each pixel can be represented by one bit (simple black and white) or up to 32 bits (high-definition color).

BITMAPPED GRAPHICS

Images which are created with matrices of pixels, or dots. Also called raster graphics.

BITNET

See Because It's Time NETwork.

BITRONICS

Specification for parallel printing which allows bidirectional communication on a Centronics type interface. Pioneered by HP, primarily for postscript printers.

BITS PER PIXEL

The number of bits used to represent the color value of each pixel in a digitized image.

BITS PER SECOND

(Bps) The speed at which a modem sends or receives information. For example, a modem that operates at 2400 bits per second can transfer 2400 binary digits each second. A character normally consists of seven or eight of these binary digits, plus the start and stop bits that separate the character from other transmitted characters.

BIU

Basic Information Unit

BL-IDM

Britton Lee Intelligent Database Machine

BLACKOUT

Total loss of utility power

BLANKING

Supression of the video signal for a portion of the scanning raster; usually during the retrace time.

BLOCK MODE

See MNP-Class 1.

BLOCK TRANSFER

Transferring a block of 64 words maximum of data to or from an I/O module in one scan. Not all Allen-Bradley I/O modules support block transfer; consult the appropriate I/O module's manual for more information.

BLOCK-CHECK CHARACTER

(BCC) The 2's complement of the 8-bit sum (modulo-256 arithmetic sum) of all data bytes in a transmission block. It provides a means of checking the accuracy of each message transmission.

BLOODY!

Virus, that on the 128th boot, displays the message "Bloody! Jun. 4, 1989" (date of the Tiananmen Square Massacre).

BLOOMING

De-focusing of the image caused by excessive brightness in the region.

BMAC

See Basic Media Access Controller.

BMAC SYSTEM INTERFACE

A component that reads and writes data to and from the FDDI packet buffer.

BNC

British Naval Connector

BNC TAP

Used with Thin Coax, has two female push-and-turn BNC connectors arranged in a T-style configuration. Also called an in-and-out connector, the T connector accepts terminated thin coax cable at both ends.

BOARD

1) A printed-circuit board. 2) A printed-circuit-board assembly - in the sense that the (printed-circuit) board is physically the main component of a printed-circuit-board assembly.

BOB

Microsoft's easy to understand GUI. Bob is supposed to be a friendly assistant of make Windows easier to use. The internal codename for the project was rumored to be Windows for Morons.

BOC

See Bell Operating Company.

BOMB

A special type of Trojan horse that remains hidden and is used as a launch pad for releasing a virus or worm attack. A particular date, time, or condition triggers the attack. If the trigger is based on a date or time, it is called a time bomb. An example of a time bomb is the Friday the 13th Virus that was triggered on the first Friday the 13th in 1988. A logic bomb is triggered by an event or logic condition. Some software developers, for example, have installed logic bombs that explode if an illegal copy is made of their software.

BONDING

An industry-standard protocol for "Bandwidth On Demand". Bonding uses the technique of inverse multiplexing to link the two B channels of a single ISDN line to form one high-speed circuit capable of running at 128 Kbps.

BOOLEAN ALGEBRA

A form of algebra that uses logic, rather than numeric calculations. Some Boolean functions are AND, OR, and NOT.

BOOT

To start a computer. The first step is to load startup instructions from the boot ROM or boot sector of a disk.

BOOT IMAGE FILE

A file located in a server's LOGIN directory that works in conjunction with a remote boot chip on a NIC or diskless workstation to boot without the aid of a local disk drive.

BOOT SECTOR

The first logical sector (sector 0) of a floppy or hard disk is designated the boot sector. A portion of a disk that contains the coded instructions for the operating system to start the computer. Every DOS-formatted disk has a boot sector whether the disk is bootable or not. A non-bootable DOS-formatted disk has a short program in its boot sector that a displays a message something like: "Non-System disk or disk error Replace and press any key when ready". When a PC is booted, a program in the computer's ROM BIOS loads into memory and executes the code in the boot sector of the first disk it finds.

BOOT SECTOR INFECTIONS

Contamination of the boot sector by a virus. Particularly serious because information in the boot sector is loaded into memory first, before virus protection code can be executed. The only certain way to eliminate boot sector infections is to restart from a disk known to be uninfected, then clean up the infection. Boot sector viruses copy the boot sector program to another location on the disk, then write a copy of their own code to the boot sector. When the computer is booted from the infected disk, the BIOS executes the virus code, which then executes the copy of the boot sector it has saved elsewhere.

BOOTP

Bootstrap Protocol A program running on a TCP/IP network that provides network nodes with IP addresses, subnet masks, and gateway addresses.

BOOTPC

Bootstrap Protocol Client

BOOTPS

Bootstrap Protocol Server

BOR

Basic Output Report

BOSS

Business Office Servicing System

BPDU

Bridge Protocol Data Unit

BPP

See Bits Per Pixel.

BPS

See Bits Per Second.

BPV

Bipolar Violations

BR-SAT-MON

Backroom SATNET Monitoring

BRANCH

An intermediate cable distribution line in a broadband coaxial network that either feeds or is fed from a main trunk. Same as a feeder.

BRANCH SEGMENT

In a single Ethernet LAN, any segment that is linked by a repeater to the backbone segment. Branch segments carry datagrams to and from stations on the branch segment to the backbone segment.

BRI

See Baasic Rate Interface.

BRIDGE

In OSI terminology, a bridge is a Data Link Layer intermediate system. A bridge usually functions at the physical and datalink layers. It joins two separate LANs (networks with common protocols) but restricts LAN frame traffic to either side of the bridge unless forwarding is required. This lets administrators isolate local traffic to their respective segments and still support communication between segments. A bridge either filters or forwards frames by reading the node address in the frame header (MAC-layer bridge), or by reading the DSAP and SSAP in an 802.2 header (LLC-bridge). Bridges process LAN frames (not network packets) and are governed by IEEE standards. A bridge should not be confused with a router, which uses an entirely different layer of protocol and information for forwarding packets (not frames). It reconditions signals like a repeater, but a bridge is more intelligent. A bridge stores and forwards complete packets while a repeater forwards electrical signals. A bridge uses ISO/OSI layers 1 or 2. For a LAN, a device that links a network to another of the same type. Also see repeater, MAC-Layer Bridge, LLC Bridge, and Router.

BRIDGED TAP

The multiple appearances of the same cable pair at several distribution points.

BRIDGING-ROUTER

See Brouter.

BRIGHTNESS

The balance of light and dark shades in an image. The amount of white included. See HSB Model.

BROADBAND

Characteristic of any network that multiplexes multiple, independent network carriers onto a single cable. This is usually done using frequency division multiplexing. Broadband technology allows several networks to coexist on one single cable; traffic from one network does not interfere with traffic from another since the "conversations" happen on different frequencies in the "ether," rather like the commercial radio system.

BROADBAND ISDN

X.25, Frame Relay, and T1 networks can be used to interconnect LANs at 2 Mbps or less. One technology under development to interconnect LANs at higher data rates is based on B-ISDN. B-ISDN was developed to respond to the need to improve the basic and primary rates provided by ISDN (Narrowband ISDN). Voice, video, data, image, and multimedia are examples of applications that require high bandwidth. Initial B-ISDN interfaces provide data-rate transmission of 51 Mbps, 155 Mbps, or 622 Mbps over fiber optic media. The physical-layer support for B-ISDN is provided by ATM and SONET. With appropriate adaptation layers, SONET and ATM can be used for LAN interconnectivity.

BROADBAND LAN

LAN which uses FDM (freq. division multiplexing) to divide a single physical channel into a number of smaller independent frequency channels. The differnet channels created by FDM can be used to transfer different forms of information - voice, data, video.

BROADBAND LINK

1) A communication link that can have multiple channels. Each channel signal modulates its own carrier frequency. Example: LAN/1 link. 2) Contrasted with carrier-band link and baseband link.

BROADCAST

A packet delivery system where a copy of a given packet is given to all hosts attached to the network. Example: Ethernet.

BROADCAST

To send a message to all users on a network.

BROADCASTING

A system that delivers a copy of a given packet to all attached hosts. You may implement broadcasting with either hardware or software. See also packet.

BROUTER

A device that can perform both bridging and routing functions. A device that routes specific protocols, such as TCP/IP and IPX, and bridges other protocols, thereby combining the functions of routers and bridges.

BROWNOUT

See Sag.

BRP

Business Recovery Plan

BSC

See Binary Synchronous Communication.

BSD

See Berkeley Software Distribution.

BSD4.2

The version of DOMAIN/IX system that implements 4.2 BSD UNIX from the University of California at Berkeley. See Berkeley Software Distribution.

BSI

See BMAC System Interface.

BT

Bismaleimide triazine - often used for the substrate of a BGA.

BTAM

See Basic Telecommunications Access Method.

BTU

Basic Transmission Unit

BTW

By the way

BUFFER

A reserved part of memory where data is held temporarily until the data is transferred from storage to another location in memory. Some printers have their own buffers.

BUFFERING

The process of using buffers to hold data being moved to or from I/O devices such as serial ports and disk drives.

BUFFERS =

In PCs, allocates memory for buffers when the system starts. These buffers help Windows read information faster from the hard disk.

BUG

A mistake in a program, sometimes called a "feature" by the program's author.

BULLETIN BOARD SYSTEM

(BBS) An electronic system in which users participate in discussions by leaving public messages for each other. Most BBS's are run on personal computers and are accessible only by dialup modem. Many have additional features, such as on-line games and a file repository. Usenet News is not a BBS in the usual sense of the word, but it provides the messaging features of a BBS on a much grander scale than found on any existing BBS.

BUMPS

A term used to describe BGA solder balls (contact points) after reflow attachment. See Ball Grid Array.

BURST AGGREGATE INPUT RATE

See Aggreaget Input Rate

BURST MODE

A mode used in MCA and EISA computers and devices to facilitate greater flow of data through the bus. When bus mastering is employed, a bus master and its slave can establish a connection and send large blocks of data without CPU intervention. Without burst mode, each byte requires CPU attention to gain control of the bus, and then to send a byte of data.

BURST MODE NCP

A variation of NCP's normal one-to-one, packet-to-acknowledgment procedure. In Burst Mode NCP, up to 64K worth of 'packet-fragments' can be acknowledged with one NCP acknowledgment packet.

BURST MODE PROTOCOL

See Burst Bode NCP.

BURST-MODE

A high speed data transfer in which the address of the data is sent followed by back-to-back data words, minimizing channel-to-channel skew.

BUS (COMPUTER)

The interface between devices in a computer. PCs incorporate bus designs that include ISA, EISA, MCA, and NuBus (Macintosh).

BUS (NETWORK)

A network that includes one circuit on which data is sent and received. Bits of data are broadcasted over a bus network; only one frame of data can occupy the bus at one time.

BUS MASTERING

A function used to off-load I/O processing to a processor on the interface card. Although some ISA boards use this technique for marginally improved performance, bus mastering is only truly effective when used with a bus design that is capable of controlling bus master access to the computer bus, as is the case in EISA and MCA computers. Bus mastering alone does not fully realize capabilities of this design unless implemented in conjunction with accessing the 32-bit burst mode and streaming data modes of EISA and MCA computers.

BUSSMASTERING

See Peripheral Component Interconnect bus.