IT Glossary

10

10Base2  Also called thin wire Ethernet coax cable. The “10” in this term indicates 10 Mbps baseband data transmission, and the “2” indicates that segments can be a maximum of 607 feet in length.

10Base5  Also called thick wire Ethernet coax cable. The “10” in this term indicates 10 Mbps baseband data transmission, and the “5” indicates that segments can be a maximum of 1640 feet in length.

10BaseT  Also called twisted pair Ethernet. The “10” in this term indicates 10 Mbps baseband data transmission, and the “T” indicates twisted pair wiring. Segments can be a maximum of 330 feet in length.
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A

ACK  Acknowledge or acknowledgment. A response indicating that a previous transmission has been received.

address  A number or group of numbers that identifies a unique node on the network.

API  Application Programming Interface. A programming language and messaging format that allows one application to interact with the functions of others.

ARCNET  Attached Resource Computer Network (ARCNET) is a low-cost token passing LAN system, transmitting digital signals one message at a time (See baseband). ARCNET communicates at a rate of 2.5 megabits per second.

ARP  Address Resolution Protocol. On aEthernet TCP/IP network, each node is identified by a physical network address and an IP address. ARP determines which network address corresponds to a given IP address.

asynchronous communications  Information transmitted as a serial stream of bits separated by a “start bit” and a “stop bit.” No clock or other timing mechanism is used.

ATM  Asynchronous Transfer Mode. A general purpose switching method for carrying voice, data, image, and video.

AUI cable  Attachment Unit Interface cable. Four twisted-pair wire cable that connects an Ethernet device (such as an adapter card) to an external Ethernet transceiver. Also called transceiver or drop cable.
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B

backbone network  A segment of network that links several individual LANs together in a single building. It can also be used to link several building LANs together in a campus environment.

Balun  BALanced UNbalanced. A device that allows interconnection between a balanced transmission line (like a twisted pair cable) and an unbalanced line (like a coax cable).

bandwidth  The data carrying capacity of a transmission line or channel, or the rate of information exchange between two systems.

baseband  A transmission method that uses cable to handle a single signal at a time.

baud  The measure of signal changes per second in a device or a connection.

BNC connector  A type of connector used to connect thin coax Ethernet and ARCNET cables.

bridge  Any device that provides a communications pathway between two or more LAN segments (or rings).

broadband  A method of conveying information over a LAN in which voice, video, or data can be carrier simultaneously.

broadband services  Sometimes called “fast packets” services, provide data rates at T1 (1.544 Mbps) or higher.

brouter  bridge router. A device that acts as a bridge and a router.

burst  A continuous transfer of data without interruption from one device to another.

bus  A cable configuration where nodes are daisy-chained together from one to the next as opposed to a star pattern.
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C

carrier  A company that provides telephone and data communications services within a Local Access and Transport Area (LATA) or between LATAs in the United States. Examples of inter-LATA carriers are AT&T, MCI, and Sprint.

CAT5  Category 5 cable supports 10 MHz data applications.

collision  When two stations try to send packets at the same time, a collision occurs. Ethernet network collisions are considered normal events. Carrier Sense Multiple Access/Collision Detect (CSMA/CD) restores service after each collision.
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D

dedicated network  A system with no other applications existing on the LAN. A dedicated network is characterized by high reliability.

Domain Name Service  Part of the TCP/IP protocol stack, DNS maps network addresses to logical names. Other TCP/IP protocols, such as Telnet and FTP, use DNS to resolve logical names to network addresses.

driver   Software that controls an input/output port or external device.
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E

EEPROM  Non-volatile, electrically programmable, read-only memory that can be erased with electrical signals.

Ethernet  A baseband network medium that communicates at 10 megabits per second.
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F

Fast Ethernet  A LAN technology that transmits information at 100 Mbps via twisted pair and fiber optic media. 100BaseT and 100VG-AnyLAN are two LAN standards that can carry Ethernet frames at 100 Mbps. Currently, Fast Ethernet is not as widely used as the 10 Mbps, twisted pair version of Ethernet. Fast Ethernet is typically used as a building backbone.

FDDI  Fiber Distribution Data Interface is a high-speed fiber optics LAN standard that uses token passing with a data transmission at 155 megabits per second.

FTP  File Transfer Protocol. A protocols associated with TCP/IP. FTP allows a TCP/IP “client” to download a file from a TCP/IP host over a LAN or WAN.

Flash memory  Non-volatile memory that can be updated with software.

frame  Sometimes referred to as “packet.” A method of packaging data or sets of bits for transmission.
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G

gateway  Any host used to route network traffic from one network to another, or to pass network traffic from one protocol to another.
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H

hop  A transmission of a data packet through a router in a system of interconnected cables and routers. The "hop count" is the number of routers the packet passes enroute to its destination.

hub  A central location for the attachment of wires from network stations. A 10BaseT Ethernet hub is a multi-port repeater in which each port connects a to station. The term “hub” can refer to many types of devices; including standalone, stackable, and chassis-based hubs for Ethernet, token ring, and FDDI networking.
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I

ICMP  Internet Control Message Protocol. Part of the TCP/IP protocol stack, ICMP is the protocol used by IP routers and hosts to send control and error messages between themselves.

Internet  The (capital"I") Internet refers to the World Wide Web of interconnected computers and computer networks that links schools, businesses, government agencies, research institutions, and other organizations. Internet (lower case “I”) refers to any inter-network of LANs linked by routers and/or bridges.

IP  Internet Protocol is a Network Layer protocol that is used by IP routers to route data packets between LANs.

IP address  Internet Protocol address. A 32-bit network address that uniquely locates a host or network. The IP address is a 4-octet address that uniquely defines the node on the network. Each octet is in the range of 0 to 255; for example 122.51.35.113. These addresses, when registered, are unique world wide. This assures connectivity compatibility if the network ever is connected on a public WAN such as the Internet.

IPX  Internetwork Packet Exchange. The Novell Network Layer protocol.

ISDN  Integrated Services Digital Network integrates data, voice,and video signals onto a digital telephone line.
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J

Jabber  The random transmission of data by a faulty device that can corrupt the transmissions of other devices.
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L

LAN  A Local Area Network is a high-speed communications system designed to link computers together within a small geographic area such as a workgroup, department, or building.

LAN cable configurations  Cable layouts for local area networks; for example bus, ring, and star. These layouts display the nodes, routers, gateways, bridges, and media being used.

link  A connection between two network entities.

local network traffic  Nodes on the same segment of a network. Packets that are sent locally do not need to follow the entire network.
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M

MAC  Media Access Control puts packets from higher protocol layers into the proper format, detects errors and handles network access.

MAN  Metropolitan Area Network is a backbone network that spans a metropolitan area. It is usually a public utility.
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N

NDIS  Network Driver Interface Specification gives network users access to several protocols from a single network adapter driver.

network administrator  The individual responsible for managing and maintaining the network.

NIC  The Network Interface Card is used to make the physical connection from a computer to a network.

node  Any device connected to a network.

NOVRAM  Non-volatile random access memory. NOVRAM retains the contents of its memory when power is turned off.
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O

octet  sequence of eight bits.

OSI  Open Systems Interconnection. A collection of international standards that define the protocols to enable connection and operation of different systems connected to a local or remote network.
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P

packet  The "envelope" that is used by nodes to send messages to one another.

packet driver  The software that works with the hardware to send and receive Ethernet packets on a network.

patch panel  Usually found in a wiring closet, a patch panel is used to make network cabling easier. A patch panel contains rows of modular jacks that can be used to terminate cable runs from network stations to hub ports.

peer-to-peer  A communication method that eliminates the need for a central computer. With a peer-to-peer network, nodes communicate equally to each other across the network. Each node stores its own programming, while it passes and receives information down the line.

PING  Packet Internet Groper. A testing utility used to assure a node can receive and transmit Ethernet messages.

PPP  Point-to-Point Protocol is designed to support transmission of packets over synchronous and asynchronous links. PPP automatically assigns IP addresses, so that remote computers can connect into an IP network at any time.

protocol  A set of rules used to define the exchange of information.
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R

repeater  A device used to extend the length, cable configuration, or connectivity of a network.

ring cable configuration  A closed loop network.

RIP  Routing Information Protocol.

RJ45  An 8-pin modular connector used on unshielded twisted pair cable primarily for 10BaseT Ethernet and token ring LANs, also used for some multi-line phones.

router  Devices that use the information in each packet to route communications from one LAN to another.
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S

shared network  A network configured with other applications on the LAN. Application support can be limited by bandwidth availability.

SIMM  Single Inline Memory Module (SIMM). High density memory chips packaged onto a small board.

SLIP  Serial Line Internet Protocol is a serial communication protocol designed to support transmission of IP packets over synchronous and asynchronous links such as dial-up telephone lines.

SMTP  Simple Mail Transfer Protocol is a message transfer protocol used in conjunction with the TCP/IP protocols on the Internet and other TCP/IP networks. It provides a store-and-forward function between the mail systems of networked computers.

SNMP  Simple Network Management Protocol.

ST  Straight Tip (ST) connector. A fiber optic connector used to join single fibers together.

star  A network cable configuration where the central control point is connected individually to all stations.

StarLAN 10  A local area network that connects nodes to hubs in a star wired bus configurations using ordinary unshielded twisted pair wire. The network communicates at ten megabits per second.

STP  Shielded Twisted Pair cable has shielding around it to provide more protection against Electromagnetic Interference.

subnet  A physical or logical subdivision of the TCP/IP network. It is sometimes referred to as the “gate”.

subnet mask  A method of representing a portion of the IP network address that is devoted to subnet addresses. This mask is used in conjunction with the IP address to determine how packets follow the network. An IP address can be divided into two parts: network address and host address. The subnetmask defines the dividing line between the two parts.

switches  Switches link several separate LANs and provide packet filtering between them. A LAN switch is a device with multiple ports, each of which can support an entire Ethernet or token ring LAN.
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T

T1/T3 Services  T1 and T3 are synchronous transmission services for delivering digital data and voice over wide area networks. “T-carrier” services use time division multiplexing to multiplex multiple voice and data channels over a single T1 or T3 circuit. The transmission rate for T1 is 1.544 Mbps, which can support 24 64 Kbps channels (64 Kbps is the standard bandwidthrequirement for one full duplex, uncompressed voice circuit). T3 runs at 44.736 Mbps and supports 28 T1 circuits.

TCP/IP  Transmission Control Protocol/Internet Protocol.

throughput  The measurement of the amount of data to be transferred through a device or system, usually expressed in bits or bytes per second.

token passing  The process of passing a token to each node that allows the node to talk on the network.

token ring  A LAN architecture that uses a “token,” passed from one network node to the next, to grant permission to transmit on the network. The token ring daisy chains nodes together to form a ring cable configuration.

transceiver  Provides the interface between the adapter card and the network.
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U

UDP  User Datagram Protocol is a connectionless network protocol for the exchange of requests and replies between hosts.

UTP  Unshielded Twisted Pair (UTP) wire; 4-wire 24/26 AWG with a RJ-45 telephone type connector. The type of wire used on 10BaseT networks.
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V

VOP  Velocity of Propagation. The speed that signals travel down a cable. It is measured as a percentage of the speed of light in a vacuum.
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W

WAN  Wide Area Network. Generally refers to a network that connects users and systems across large distances and usually employs telephone or other long range communications.
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X

X.25  A protocol used in wide area packet-switched data networks.
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