A form of Ethernet and IEEE 802.3 network cabling, using thin coaxial cable. The term refers to 10Mbps (speed) BASEband (transmission) 200 metres (maximum length actually 185 metres). Commonly known as 'Cheapernet'.

10BASE-5

A form of Ethernet and IEEE 802.3 network cabling, using thick coaxial cable. The refers to 10Mbps (speed) BASEband (transmission) 500 metres (maximum length).

10BASE-T

A form of Ethernet and IEEE 802.3 network cabling, using twisted-pair cabling. The term refers to 10Mbps (speed) BASEband (transmission) twisted-pair cable. 10 BASE T recommends a segment length of 100 metres. In almost all applications in use today this technology is run at 100Mbps.

ANSI

American National Standards Institute.

AppleTalk

A proprietary network system designed by Apple Computer, principally used with Macintosh systems.

Application Layer

OSI standard for reading, writing, sharing and administering files on different machines.

ARCnet

A proprietary network system designed by Data-point Corporation using token Bus techniques.

ARPANET

The Defence Advanced Research Projects Agency Network. A network in America which was used to develop the Internet Protocol Suite, source of TCP/IP protocols and many others such as OSI.

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ASCII

American Standard Code for Information Interchange

ATM

Asynchronous Transfer Mode, a high-speed, scalable cell-switching protocol that breaks packets down into fixed 53-byte cells.

AUI

Attachment Unit Interface. Defined in IEEE 802.3 as the interface between the transceiver and the network device.

Back Pressure

A technique for preventing buffer overload by sending a jam signal when a station tries to send to an overloaded port. The sending station will interpret the signal as a collisions, stop sending and try again later.

Baseband

A transmission technique employed in LANs. Only one device can communicate at one time and a device simply sends its digital signal on to the cable without any modification.

Bridge

A device which connect two separate networks at the MAC layer and passes data between the two networks, filtering local communications.

Broadband

Analogue transmission technique employed in LANs. The signals on the network are divided, (usually by frequency division), to allow more than one (usually pairs of signals) on the cable at any one time. This form of communication requires modems for all devices wishing to access the network.

Bus

A form of network structure based on a single length of cable to which all network devices are connected. Ethernet is an example of such a network structure.

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Bit

An abbreviated form of Binary digit used to represent a single transition on a data line, or a fraction of a byte.

Byte

A unit of computer information, consisting of eight bits (binary digits).

CAD

Computer Aided Design.

CCITT

Comite Consultatif Internationale de Telegraphique et Telephonique. A standards body concentrating on the definition of European Communications Standards.

Cheapernet

A term generated following a revised specification for Ethernet using a thin, lower cost, coaxial cable.

CLNS

ConnectionLess-mode Networking Service as defined in ISO 8473, operating at level 3, Network, of the OSI reference model.

Coaxial cable

A cable consisting of a single inner core surrounded by insulators and a stranded metal sheath, all encased in a single insulating outer cover.

Comite Consultatif Internationale de Telegraphique et Telephonique

See CCITT

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CONS

Connection-mode Network Service. Operates at the Network Layer (layer 3) and implements a connection-oriented networking system using X.25.

Connection Oriented Protocol

A form of transmission where a connection is established across a network proper to the first transmission of data taking place. The connection handles checking and error recovery during transmission thus incurring a connection overhead on the transmission.

ConnectionLess Network Service

See CLNS

Connectionless Protocol

A form of transmission where no communication takes place prior to the first transmission of data. Therefore no connection is made on the network and no checking takes place during transmission thus reducing the connection overhead on the transmission.

CSMA/CA

Carrier Sense Multiple Access with Collision Avoidance. A method of network access not covered by OSI standards. This technique is implemented on AppleTalk networks.

CSMA/CD

Carrier Sense Multiple Access with Collision Detect. The technical reference to the standard LAN transmission network utilising a bus structure, conforming to IEEE 802.3 and ISO 8802-3 which were based on the Ethernet network standard.

Cut-through Switching

A switch forwarding method designed to minimise delay. A packet is forwarded to the output port as soon as the destination address is known.

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Data Link

Layer 2 of the OSI 7-layer model.

Datagram

A unit or packet of data sent across a network. A datagram is self contained, with source and destination address, but is not necessarily a complete communication, which may require many such datagrams.

DDCMP

Digital Data Communications Message Protocol. A form of transmission for wide area connectivity over DECnet.

DECnet

A network architecture produced by Digital Equipment Corporation encompassing local and wide area connectivity.

Distributed Systems Gateway

DSG. A device which operates at layer 4 of the OSI reference model and allows interconnection of dissimilar networks.

DIX DEC, Intel and Xerox

These terms are used in relation to the published Ethernet Specifications.

Early Token Release

A modified version of token passing where a device does not have to wait for its communication to circle a network before transmitting the token on around the network.

Ethernet

A LAN transmission network utilising a bus structure, first produced by Xerox in the USA, later adopted by both DEC and Intel as well (see DIX). This was later adapted to create the IEEE 802.3 and ISO 8802-3 standards (see CSMA/CD).

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EtherTalk

An Ethernet implementation of the lower two layers of the AppleTalk protocol suite. EtherTalk complies with 802.3.

FDDI

Fibre Distributed Data Interface. A token passing ring network specification developed by ANSI, implementing dual optical fibre rings. The network operates at 100Mbps and can be up to 100 kilometres in length.

Fibre Distributed Data Interface

See FDDI

Fibre Optic Cable

A cable type based on a continuous strand of very fine glass which uses light to carry information. This type of cable is able to carry very high levels of data for great distances without interference.

File Server

A device, usually a PC, offering on-line storage and management of files for more than one device on a network. File servers offer storage and recall of data files and applications. Additionally they may offer sharing of files and applications, protocol conversion and central facilities such as electronic mail.

File Transfer Protocol

See FTP.

Fragment Free

A switch forwarding method that offers fixed delay whilst ensuring only valid frames are forwarded.

FTAM

File Transfer, Access and Management

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FTP

File Transfer Protocol. A Protocol from the Internet Protocol Suite which provides transfer of files between two dissimilar machines.

Full-duplex

Two-way communication in which a station can send and receive data simultaneously, therefore doubling the bandwidth.

Gateway

A device used to allow conversion on LAN networks. Normally operating a layer 4 or above in OSI terms. Gateways convert information between two different networks, computers or applications.

Half-duplex

A communication method in which a station can either send or receive data, not both at the same time.

Half Repeater

A device which extends the distance a LAN can cover by joining two lengths of cable over another communication medium, such as a dial-up circuit, and regenerating the signal.

Head End

A device used with Broadband networks. This is positioned at one end of the cable to convert the signal from one channel and output it on the other channel.

Host Servers

A device which connects to a LAN and then allows a computer, which cannot directly support LAN protocols, to connect to it providing all necessary LAN support.

IEEE

Institute of Electrical and Electronic Engineers. An American Institute responsible for developing and publishing many communications standards (see section listing Standards).

IMAGE

A file format used within the Internet Protocol Suite for handling graphics

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Institute of Electrical and Electronic Engineers

See IEEE

Integrated Services Digital Network

See ISDN

Interworking

A term extending beyond communication any relating to hardware and software compatibility not just to allow connection but to maximise operational efficiency.

International Standards Organisation

A suite of network protocols originally designed for ARPANET in America and since adopted as the main de facto protocols for LANs.

ISDN

A form of public network that is designed to handle voice and data at high speed in digital format.

ISO

International Standards Organisation. An organisation devised to create standards which will promote internetworking between different vendors equipment. The main focus of communications is implementation of the Open Systems Interconnection (OSI) reference model.

LAN

See Local Area Network.

LAN Manager

A networking communication system operating on OS/2-based PCs, plus other systems produced by Microsoft and 3Com.

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Laser Printer

A high quality printing device capable of producing totally free format image output.

Latency

The time delay introduced by a network device. The time taken for the device to receive a frame and begin sending it out again.

LF

Line field used to identify the protocol in use.

LLC

Logical Link Control. The upper of the two sub-layers in layer 2 of the OSI 7 layer model.

Local Area Network

A system for intercommunication between computer terminals, PCs and related equipment operating within the same general area.

LocalTalk

A twisted pair transmission system used with Macintosh networks, designed by Apple Computer.

Logical Link Control

See LLC.

Logical Ring

When token passing is implemented on a Token Bus network, the token cannot circulate as on a Token Ring network. A Logical Ring is implemented where each device is given a sequential address. When a taken is relayed on the network each receiving address attaches the next logical device address thus ensuring circulation of the data.

MAC

Media Access Control. The lower of the two sub-layers in layer 2 of the OSI 7 layer model.

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MAN

Metropolitan Area Network. A term often used to describe the latest, high speed and long distance LANs, such as FDDI.

MAP

Manufacturing Automation Protocol. An OCI initiative pioneered by General Motors to create a series of standards for computer and communication s equipment interworking on the production floor, for example central computer to production line robot.

MAU

Multi-station Access Unit. A device for use on IBM Token Ring networks that allows terminals, PCs, printer and other devices to be connected in a star-based configuration.

Media Access Control

See MAC.

Metropolitan Area Network

See MAN.

MMFS

Manufacturing Message Format Standard. An OSI Application Layer standard devised for MAP type networks.

Multi-station Access Unit

See MAU.

Netbios

A network communication system operating on MS/DOS PC networks.

Netware

A suite of application oriented interface protocols designed for use on LANs and produced by Novell.

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Network Layer

Layer 3 of the OSI reference model which allows interconnection of dissimilar networks (see Distributed Systems Gateway).

Non-deterministic

A term relating to the inability of a designed being able to predict the performance or delay on a network where collision is possible.

Open Systems Interconnection

See OSI

OSI

Open Systems Interconnection. The term defined by the International Standards Organisation as a basis for standards to enable different vendor systems to interwork without modification.

PC

Personal Computer.

PDU

Protocol Data Unit. Protocol Data Units are the datagrams relating to Logical Link Control (LLC) transmissions.

Physical Layer

Layer 1 of the OSI reference model Presentation Layer, Layer 6 of the OSI reference model Probabilistic. A term relating to the ability of any one device being able to communicate on a network where collision is possible.

Protocol Data Unit

See PDU.

PSU

Power Supply Unit.

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RAM

Random access memory used to temporarily store data in a CPU.

Rat’s Tail

A term used to describe the network adapter used to connect Apple Macintoshes to a LocalTalk LAN.

Repeater

A device which extends the distance a LAN can cover by joining two lengths of cable and regenerating the signal.

RG58

A coaxial cable, often referred to as 'Thin' coax. This was introduced to reduce the costs of cabling early networks, particularly Ethernet. This version became known as 'Cheapernet'.

Router

A device which connects two separate networks at the Network Layer. It operates in a similar way to a bridge but also has the ability to choose routers through a network. Because a router operates at the Network Layer it is protocol-dependent.

Segment

In bus structure network this refers to a single length of cable and attached devices which would normally be linked to another segment by a repeater.

Session Layer

Layer 5 of the OSI reference model.

Simple Mail

See SMTP

Store-and-Forward

A forwarding technique designed to avoid propagating bad frames. The frame is full loaded and checked before any of it is sent out again.

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Transfer Protocol SMTP

Simple Mail Transfer Protocol. A protocol from the Internet Protocol Suite which provides electronic mail transfer across a network.

SNA

Systems Network Architecture. An architecture and suite of protocols designed and produced by IBM for hierarchical computer networks.

Structured Wiring

A cabling philosophy which endeavours to minimise cable changes once a building has been wired.

TAP

A connection into the Local Area Network cable.

TCP/IP

Transmission Control Protocol/ Internet Protocol. Two main network communication protocols, part of the Internet Protocol Suite.

Technical and Office Protocols

See TOP.

TELNET

A protocol from the Internet Protocol Suite which provides a Virtual Terminal interface for communicating devices.

Terminal Servers

A device which connects to a LAN and then allows one or more terminals, which cannot directly support LAN protocols, to connect to it providing all necessary LAN support.

Token

A token is a special sequence of data which is passed around a network sequentially. When the token is captured by a device it flags it as busy and adds data to the frame. Once the transmission has circled the network the busy token is replaced by a free token which the next device can then capture and transmit.

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Token Bus

A LAN transmission network utilising a bus structure and implementing token passing access. This network is detailed by the IEEE 802.4 and ISO 8802-4 standards.

Token Ring

A LAN transmission network utilising a ring structure. The most common form is IBM Token Ring. This network type is detailed by the IEEE 802.5 and ISO 8802-5 standards.

TokenTalk

A Token Ring implementation of the lower two layers of the AppleTalk protocol suite.

TOP

Technical and Office Protocols. An OSI initiative pioneered by Boeing Computer Services to create a series of standards for computer and communications equipment interworking in the office environment.

Transmission Control Protocol/Internet Protocol

See TCP/IP.

Transport Layer

Layer 4 of the OSI reference model.

Twisted Pair Cable

The most common form of communication cabling used by telephones, computer terminals and LANs. A pair of wires, coated in a plastic sheath are twisted together. In most cases several pairs are then bound in a single sheath and then laid as a single cable using multiple twisted pairs.

VDU

Visual Display Unit.

Video Conferencing

A form of communication requiring very high capacity networks, which transmits pictures of all parties as well as voice.

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Virtual Network

A form of network where communication and access is a achieved without any knowledge of the network structure or location of a specific resource.

WAN

Wide Area Network. A network which uses public or private circuits to link terminals, PCs and computers over long distances that also often allows some user choice in destination. Followings the implementation of routers, bridges and gateways many LANs are becoming Wide Area Networks, but more typically networks such as X.25 are classed as WANs.

X.400

An Application Layer OSI standard for transferring electronic mail on a store and forward basis between different machines.

XNS

Xerox Networking Systems. An Ethernet network produced by the Xerox Corporation.

Yellow cable

A coaxial cable, often referred to as 'Thick' coax. This was the first cable used on may early LANs.

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