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Technical Glossary

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100Base-FX - This Fast Ethernet standard (IEEE 802.3u) supports 100Mbps, full-duplex data transmission over fibre optic cable.

100Base-T - A high-speed version of Ethernet (IEEE 802.3). Also called Fast Ethernet, 100Base-T transmits at 100Mbps.

100Base-TX - A popular implementation of the 100Base-T Fast Ethernet standard. It specifies data transmission over two-pair (four-wire) Category 5 unshielded twisted-pair (UTP) cable.

10Base-F - An Ethernet standard for a fibre optic star topology.

10Base-FB - The portion of the 10Base-F standard that defines the requirements for synchronous data transmission over a fibre backbone.

10Base-FL - The portion of the 10Base-F standard that defines a fibre optic link between a concentrator and a station.

10Base-FP - A star-coupled network for a 10Base-F network.

10Base-T - An Ethernet standard that uses twisted-wire pairs.

10Base2 - An Ethernet standard that uses a thin coaxial cable. Also called Thin Ethernet, ThinWire and ThinNet.

10Base5 - The original Ethernet standard that uses a thick coaxial cable. Also called Thick Ethernet, ThickWire and ThickNet.

A & B Bit Signalling - A T1 transmission method in which one bit of every sixth frame on each of the 24 sub channels carries supervisory signalling information.

AAA - Authentication, Authorisation, Accounting.

AAL - A connection made by the AAL between entities in the next higher level.

ABM - In HDSL transmissions, a method of data communication that allows two peer stations, either of which can initiate transmission, to link point-to- point.

Access List - In a router, a list of which addresses are allowed access to which services. An access list is used to control traffic both to and from the router.

Access Method - A software routine, which is part of the operating system or network control program and performs the storing, retrieval and transmission data functions.

Access Server - Gives LAN or WAN access to async devices.

Access Time
A) the amount of time it takes a storage device to actually read or write information.
B) Time spent connected to the Internet or to an on-line service.

Active Hub - A hub that includes a signal amplifier.

Active Link - A logical communications circuit that is established only for the duration of communications, that requires a call-set-up and call-clearing procedure for every connection.

Active Monitor - In Token Ring, the device that performs such network-management duties as keeping track of tokens and weeding out frames that would otherwise circulate indefinitely. The device that has the highest MAC address in the Token Ring is automatically selected as the active monitor.

Active Matrix - A type of LCD monitor panel that has three transistors (red, green, blue) for each pixel that produces brighter, sharper colour than passive-matrix displays and can be viewed from a wider angle.

Address
A) the number of a specific memory or peripheral storage location.
B) the number assigned to a node on a network.

Address Mapping - The translation of addresses from one protocol's format to another, so that equipment using the two different protocols can work together.

Address Resolution - Any means of overcoming the differences between two different address systems on a network. In particular, a means of mapping addresses at the Network Layer in the OSI model to addresses in the Data Link Layer.

ADSL - A telephone line with uneven transmission rates; half the transmission can attain speeds up to 640kbps; the other half can attain speeds up to 1.544Mbps or greater in the opposite direction.

Agent - A component of network- and desktop-management software, such as SNMP, that gathers information from the MIB.

Alignment Error - An error in IEEE 802.3 networks, usually caused by collisions, where the total number of bits in a frame received from the network is not a multiple of 8.

Alternate Routing - The ability to use another transmission path if the regular route is unavailable.

Analog
A) electrical signals analogous to the original sounds.
B) a transmission mode in which data is represented by a continuously varying electrical signal to be transmitted over ordinary phone lines.

Anonymous FTP - FTP access to public files on a server without the need for a password or user name.

API - A language and message format used by an application program to communicate with an operating system or other system program.

AppleShare - Software from Apple that turns a Macintosh into a file server.

AppleShare PC - Software from Apple that enables a PC to connect to an AppleTalk network.

AppleTalk - An Apple local area network architecture that supports the proprietary LocalTalk access method as well as Ethernet and Token Ring.

Application Level - The highest of the seven-layer OSI model, structure containing all user or application programs.

Application Software - Any software designed to do useful work, such as a database, word processor or spreadsheet.

ARM - In HDLC, a mode of communication where any of one primary station and one or more secondary stations can initiate communication.

ARP - A low-level TCP/IP protocol used to get a node's physical address when only its logical IP address is known.

ARPANET - Advanced Research Projects Agency Network: This packet-switching technology was the precursor of today's Internet.

ASCII - Pronounced 'askey'. A binary code for text as well as communications and printer control. ASCII is a 7-bit code providing 128 character combinations.
Asynchronous Communication Data transmission in which each transmitted character is sent without a synchronizing clock between the transmitter and the receiver. Each character is a self-contained unit with its own start- and-stop bit, used to synchronize the receiver's internal clock.

AUI - The network interface used with standard Ethernet, a 15-pin socket.
Auto-reconfiguration In Token Ring networks, the ability to reconfigure the network to bypass failures.

Auto Sensing - Automatically adjusting to different operating conditions. For example, an auto-sensing power supply will provide the correct power level whether it's plugged into 115- or 230-volt power.

B Channel - A 64-kbps ISDN user channel that carries digital data or a PCM-encoded digital voice.

Backbone - A high-capacity network that links other lower capacity networks together. It often employs the highest-speed transmission paths in the network and may also run the longest distance.

Balanced Configuration - A point-to-point HDLC configuration in which two stations are combined.

Balanced Line Interface - An interface standard that incorporates balanced transmission fro data and/or control signals with a pair of transmitters for each signal and a differential voltage reference between the pair. Capable of high-speed transmissions with less susceptibility to noise, as well as greater distance.

Bandwidth
A) the transmission capacity of a computer channel, communications line or bus.
B) the difference between the lowest and highest frequencies in a transmission channel.

Baseband - A transmission where digital signals are places onto a transmission line with no change in their modulation and use the full-channel bandwidth.

Bi-directional - Able to send data in both directions.

Binary - Having two possible states. Binary numbers have only two possible digits 0 or 1. In computers each binary digit is one bit.

Bipolar Signal - A method of transmitting binary digits in which successive marks, equal in amplitude, normally alternate between positive and negative polarity and where a space designates zero amplitude.

Bit Rate - The transmission speed of binary coded data.

Broadband - A technique for sending data, voice and video traffic over long distances by transmitting high-frequency signals over coaxial or fibre optic cables.

Bypass Relay - Feature of a Token Ring device that enables it to be shut down and removed from the ring without affecting ongoing operation of the network or the remaining devices.

Cable Modem - A modem used to connect a computer to a cable TV system that offers online services and Internet access at multi-megabit speeds far faster than that possible with conventional dialup analogue modems.

Cache - A dedicated bank of high-speed memory or a reserved section of regular memory used to boost computer performance by providing a temporary storage area for instructions.

CAD/CAM - The integration of CAD and CAM. Products designed by CAD are input directly into the CAM system.

Carrier Frequency - A unique frequency used to carry data within its boundaries; measured in cycles per second, or Hertz (Hz).

Coaxial Cable - Commonly called coax. A high capacity cable used in communications and video that contains an insulated solid or stranded solid or stranded wire surrounded by a solid or braided metallic shield, wrapped in a plastic cover.

Communication Server - A computer with a pool of modems that provides outside-line connection from a computer to remote terminals or from a LAN to remote users.

Configuration - The makeup of a system which includes hardware and software settings.

Control Panel - A set of utilities that change various aspects of the systems behaviour; for example, the colour of the background, the port to which printer data is sent, the speed of the mouse cursor etc.

Control Signal - An interface signal used to announce, start, stop or modify a function; for example, carrier detect is an RS-232 control signal that announced the presence of a carrier.

Cross talk - Interference from an adjacent communication channel.

D Channel - This 16-kbps channel is used to signal the telephone company computer to make calls, put them on hold and activates features such as conference calling and call forwarding. It also receives information about incoming calls as in caller ID.

DaisyChain - To connect devices in a series, one after the other where the transmitted signals go to the first device, then to the second and so on.

Data Bus - An internal pathway across which data is transferred to and from the processor.

Data Link
A) the physical interconnection between to points (OSI Layers 1 and 2),
B) also refers to the modems, protocols and all hardware and software needed to perform the transmission.

Data PABX - Its used solely for data to set up and break connections on demand between computers, terminal and peripherals.

Data Stream - The continuous flow of data from one place to another.

Data Transmission - Sending data over a communications network.

Data Link Layer - Layer 2 in the OSI Model. Its the part of the network that establishes, maintains and releases data link connections between adjacent elements in a network.

Database Server - A computer in a LAN dedicated to database storage and retrieval.

Dedicated LAN - In switched networks, its the network segment assigned to one device.

Designated Bridge - When forwarding a frame from a segment to the root bridge, its the bridge with the lowest path cost.

Designated Router - A router that looks for the shortest path and most efficient way to route the data, reducing the routing protocol traffic and the topological database.

Dialup Line - A two-wire line used in the Public Switches Telephone Network (PSTN)

Dialup Network - The switched telephone network regulated by government and administered by common carriers.

Digital Loopback - A technique for testing the digital processing circuitry of a communications device that can be initiated locally, or remotely via a telecommunications circuit.

Digital PBX - A modern PBX that uses digital methods for switching.

Disaster Recovery - A plan for duplicating computer operations after a catastrophe such as fire or earthquake. It includes routing off site back-up.

Domain - All possible values contained in a particular field for every record in the file. All resources under control of a single computer system. A subnetwork comprised of a group of clients and servers under the control of one security database. A group of molecules that makes up one bit on magnetic storage mediums. A named group that has control over the groups under it, which may be domains themselves. Addresses that are catalogued by type of organisation or domain.

Domain Name - The part of an Internet address that identifies the address domain.

DOS Command - An instruction that DOS executes from the command line or from a batch file.

Download - To transmit a file from one computer to another.

Drop Cable - In LANs, a cable that connects the main network cable or bus and the data terminal equipment

Dynamic Routing - A routing system that automatically adapts to network topology or traffic changes.

Emulator - Hardware that simulates another type of device or software that enables a computer to simulate the operations of another device or a different type of computer.

Encapsulation - Taking data formatted for one protocol and enclosing it within another protocol in order to transmit the data successfully across a type of network the original protocol was not designed for.

Ethernet Address - A unique 48-bit number maintained by the IEEE and assigned to each Ethernet network adapter.

Faceplate - The panel on a device containing the main brand and product name labels, as well as labels and cut outs for major external indicators or controls.

Fast Ethernet - Generally refers to 100Base-T but may also include 100VG

File-Sharing Protocol - A communications protocol that provides a structure for file requests between stations in a network.

Firewall - A network node set up as a boundary to prevent traffic from one segment to cross over to another. Firewalls are used to improve network traffic as well as for security purposes.

Flash Memory - A memory chip that holds its content without power but must be erased in fixed blocks rather than single bytes. Block sizes typically range from 512 bytes to 256KB.

Frame Relay - A high speed packet switching protocol used in wide area networks. Frame relay provides for a granular service up t DS1 rates of 1.544Mbps and is suited for data and image transfer.

Framing - A control procedure used with multiplexed digital channels such as T1 carriers, whereby bits are inserted so that the receiver can identify the time slots that are allocated to each sub channel.

Gateway - A computer that performs protocol conversion between different types of networks or applications.

Gigabit - One billion bits; used to describe data transfer rates as a function of time, as in Gbps.

Gigabit Ethernet - Technology that adapts the Ethernet model for data transmission at 1Gbps or higher.

Gigabyte - 1,073,741,824 bytes, equal to 1024 Megabytes; becoming the new basic unit of mass storage.

Gigahertz - A unit of frequency measurement; one gigahertz is equal to one billion events per second. Frequencies in this range are usually called microwaves.

IMAP - Method of accessing e-mail messages kept on a shared mail server.

In-Band Signalling - A transmission occurring in the frequency range normally used for data transmission.

Infrared - Electromagnetic waves with a frequency range between microwaves and the visible spectrum.

Intelligent Terminal - A terminal with built-in processing capability but no local disk or tape storage.

Interface Converter - A device that enables two systems with incompatible electrical signals connectors and handshaking to communicate with each other.

Internal Modem - A modem that plugs into an expansion slot within the computer.

Internet Access Provider - An organisation that provides access to the Internet.

Intranet - A network connecting a related set of standard Internet protocols and files in HTML format with employees using Internet browsers in an organisation's network and within the corporate firewalls.

IP Address - A 32-bit address assigned to hosts using TCP/IP. It belongs to one of five classes (A-E) and is expressed as 4 octets separated by periods formatted as dotted decimals. Each address has a network number, an optional sub network number and a host number. The first two numbers are used for routing, while the host number addresses an individual host within the network or sub network. A subnet mask is used to extract network and sub network information from the IP address.

ISDN - Terminal Adaptor A device that attaches a computer and an analogue or telephone to a digital ISDN line.

Jabber - An error condition where a network device continually transmits random meaningless data onto the network. In IEEE 80.3 a data packet with a length that exceeds the prescribed standard.

Java - Object orientated program language developed by Sun Microsystems. It is used extensively on the Web, most often for applets. Java is also used to solve programming problems.

KVM Switch - Keyboard, Video and Mouse Switch.

LAN Local Area Network - a communications network made up of servers, workstations, a network operating system and a communications link that servers users within a confined geographical area.

LAN Manager - A distributed network operating system developed by Microsoft, that supports a variety of protocols and platforms.

LAN Switch - A high speed switch that forwards packets between data-link segments.

Layer 3 Switching - A technology that integrates routing with switching to yield very high routing throughput rates in the millions of packets per second range.

Leased Line - A private communications channel, leased from a common carrier in a point to point or multipoint configuration. Also called a private line.

Legacy Systems - A mainframe or minicomputer information system that has been in existence for a long period of time.

Line Adaptor - A device that converts a digital signal into a form suitable for transmission over a communications line and vice versa.

Line Modulation - The means by which a carrier is varied to represent a signal carrying information.

Link Layer - Layer two of the OSI reference model; also known as the data link layer.

Local Bridge - A bridge that connects networks within the same geographical area.

Local Bus - A type of bus with a very short signal path between main processor and I/O processor.

Local Channel Loopback - A digital loopback test that forms the loop at the input to a local DCE.

Local Digital Loopback - A digital loopback test that forms the loop at the DTE side of a local DCE.

Mac Address - In LANs, a standardized data-link layer address thats required for every connected port or device.

Mac IP - A network layer protocol that encapsulated IP packets in DDP packets for transmission over AppleTalk. MacIP also provides proxy ARP services.

Mainframe - A large scale computer system that can house comprehensive software, several peripherals and networks with multiple users.

MAN - Municipal Area Network - a communications network that covers a geographical area such as a city.

Megabyte - 1,048,576 bytes, equal to 1024 kilobytes; the basic unit of measurement of mass storage.

Megahertz - A unit of frequency equal to 1,000,000 cycles per second.

Memory Card - A credit card sized memory module used as an additional disk or disk alternative in laptops and palmtops.

MSAU - Multi Station Access Unit - a central hub in a Token Ring LAN

Multilayer Switch - A switch that filters and forwards packets based on MAC addresses and network addresses.

Multimedia - Disseminating information in more than one form, including the use of text, audio, graphics, animated graphics and full motion video.

Multiplatform - Able to run on more than one type of computer.

Multipoint Access - User access in which more than one terminal equipment is supported by a single network termination.

Network Access Control - Circuits that dictate when individual workstations may transmit messages within a LAN.

Network Layer - Layer 3 of the OSI reference model. This layer provides connectivity and path selection between two end systems.

Operating System - The software of a computer that controls the execution of programs, input/output, resource scheduling and data management.

Optical Fibre - Any filament or fibre made of dielectric materials, that is used to transmit laser or LED generated signals.

Out-of-Band Signalling - Control signalling that uses an extra signal transmitted alongside the main information signal.

PABX - Private Automatic Branch Exchange - an in-house telephone switching system that interconnects telephone extensions to each other, as well as to the outside telephone network.

Patch Cable - A short cable used to make a connection between two nearby components.

Patch Panel - A group of sockets that function as a manual switching centre between incoming and outgoing lines in a communications, electronic or electrical system.

PC Card - The name for an accessory card for PCs that follows the standards set by PCMCIA.

Peripheral - Any hardware device connected to a computer, such as a monitor, keyboard, printer etc.

Plug and Play - Also known as PnP, an Intel standard for the design or PC expansion boards that the IRQ and DMA settings and I/O and memory addresses self- configure on start-up.

Protocol Analyzer - A diagnostic tool for displaying and analysing communications protocols.

Rackmount - Components that are built to fit in a metal frame which can be installed in a cabinet; usually 19" wide.

RAM - The computers primary workspace where the contents of each byte can be accessed directly without regard to the bytes before or after it.

Real Time - An operating mode that allows immediate interaction with data as it is created.

Remote Access - The ability of a computer in one location to connect to a device that is at another location or site.

RSA - A highly secure encryption method that used a two-part key.

Serial Transmission - Method of data transmission in which the bits of a data character are transmitted sequentially over a single channel.

Shared Access - An access method that enables many stations to use the same transmission medium in a LAN

Terminal Adaptor - A device used to connect ISDN basic rate interface connections to existing interfaces such as RS-232.

Terminal Emulation - A software application that makes a computer appear to a remote host as a directly attached terminal.

Terminal Server - A communications processor that connects one or more asynchronous devices such as terminals, printers, hosts and modems to an Ethernet LAN or WAN that uses TCP/IP, X.25 or LAT protocols.

Transceiver - A hardware device that links a node with a baseband network backbone, enabling transmitting and receiving capabilities.

Twisted-Pair - A cable with two conductors twisted as a pair.

Video Bandwidth - The maximum display resolution of a video screen, measured in MHz and calculated by horizontal x vertical resolution x refreshes/sec.

Video Card - An expansion board that plugs into a desktop computer, converting the images created in the computer to the electronic signals required by the monitor.

VLAN - A group of devices on a LAN or LANs that are configured for communications as if they were attached to the same wire, when in reality they are located on a number of different LAN segments.

VPN - Virtual Private Network

WAN - A data communications network spread across a wide geographical area and incorporating a large number of users. A WAN often uses transmission devices provided by common carriers.

Whiteboard Collaboration - Software that enables two users to share a computer screen in a similar manner to using a whiteboard in a meeting room.

Wireless LAN - A LAN in which data flows by radio or infrared transmissions, rather than over wire.