10Base2 - Ethernet specification for thin coaxial cable, transmits signals at 10 Mbps (megabits per second) with a distance limit of 185 meters per segment.
10Base5 - Ethernet specification for thick coaxial cable, transmits signals at 10 Mbps (megabits per second) with a distance limit of 500 meters per segment.
10BaseF - Ethernet specification for fiber optic cable, transmits signals at 10 Mbps (megabits per second) with a distance limit of 2000 meters per segment.
10BaseT - Ethernet specification for unshielded twisted pair cable (category 3, 4, or 5), transmits signals at 10 Mbps (megabits per second) with a distance limit of 100 meters per segment.
100BaseT - Ethernet specification for unshielded twisted pair cabling that is used to transmit data at 100 Mbps (megabits per second) with a distance limit of 100 meters per segment.
1000BaseTX -Ethernet specification for unshielded twisted pair cabling that is used to transmit data at 1 Gbps (gigabits per second) with a distance limitation of 220 meters per segment.
Asynchronous Transfer Mode (ATM) - A network protocol that transmits data at a speed of 155 Mbps and higher. It is most often used to interconnect two or more local area networks.
AppleTalk - Apple Computer's network protocol originally designed to run over LocalTalk networks, but can also run on Ethernet and Token Ring.
AUI Connector (Attachment Unit Interface) - A 15 pin connector found on Ethernet cards that can be used for attaching coaxial, fiber optic, or twisted pair cable.
Bit - Binary digit in the binary numbering system. Its value can be 0 or 1. In an 8-bit character scheme, it takes 8 bits to make a byte (character) of data.
Bridge - Devices that connect and pass packets between two network segments that use the same communications protocol.
Byte - an 8-bit long binary value, which originally mapped to text character values (between 0 and 255 decimal). For example, a decimal value of 65, represented in a binary byte is "01000001" and represents the capital letter "A". A byte also is the atomic value of data storage, so a megabyte is the amount of memory required to store a million bytes.
Client/Server - A networking system in which one or more file servers (Server) provide services; such as network management, application and centralized data storage for workstations (Clients).
CSMA/CA - Carrier Sense Multiple Access Collision Avoidance is a network access method in which each device signals its intent to transmit before it actually does so. This prevents other devices from sending information, thus preventing collisions from occurring between signals from two or more devices. This is the access method used by LocalTalk.
CSMA/CD - Carrier Sense Multiple Access Collision Detection is a network access method in which devices that are ready to transmit data first check the channel for a carrier. If no carrier is sensed, a device can transmit. If two devices transmit at once, a collision occurs and each computer backs off and waits a random amount of time before attempting to retransmit. This is the access method used by Ethernet.
Coaxial Cable - Cable consisting of a single copper conductor in the center surrounded by a plastic layer for insulation and a braided metal outer shield.
Concentrator - A device that provides a central connection point for cables from workstations, servers, and peripherals. Most concentrators contain the ability to amplify the electrical signal they receive.
DIN - A plug and socket connector consisting of a circular pattern of pins in a metal sleeve. This type of connector is commonly seen on keyboards.
Dumb Terminal - Refers to devices that are designed to communicate exclusively with a host (main frame) computer. It receives all screen layouts from the host computer and sends all keyboard entry to the host. It cannot function without the host computer.
Ethernet - A network protocol invented by Xerox Corporation and developed jointly by Xerox, Intel and Digital Equipment Corporation. Ethernet networks use CSMA/CD and run over a variety of cable types at 10 Mbps (megabits per second).
Expansion Slot - Area in a computer that accepts additional input/output boards to increase the capability of the computer.
Fast Ethernet - An Ethernet standard that supports 100 Mbps using category 5 twisted pair or fiber optic cable.
Fiber Distributed Data Interface (FDDI) - A network protocol that is used primarily to interconnect two or more local area networks, often over large distances.
Fiber Optic Cable - A cable, consisting of a center glass core surrounded by layers of plastic, that transmits data using light rather than electricity. It has the ability to carry more information over much longer distances.
File Server - A computer connected to the network that contains primary files/applications and shares them as requested with the other computers on the network. If the file server is dedicated for that purpose only, it is connected to a client/server network. An example of a legacy client/server network is Novell Netware. All the computers connected to a peer-to-peer network are capable of being the file server. Most modern operating systems can operate as servers or as clients, greying the distinction in the server architecture.
Firewall - A security device which inspects traffic entering and leaving a network, and allows or disallows the traffic, depending on rules describing acceptable use of the network, by filtering out unwanted packets. The firewall is usually positioned as the gateway device to another network, such as the internet. Many routers now contain firewalls. A personal firewall is usually software that runs on a workstation or server to filter unwanted traffic at the individual machine.
Gigabit Ethernet - An Ethernet protocol that raises the transmission rates to 1 Gbps (gigabits per second). Most school, corporate, and household networks provide gigabit ethernet to the workstations via cabled connections.
Hub - A hardware device that contains multiple independent but connected modules of network and internetwork equipment. Hubs can be active (where they repeat signals sent through them) or passive (where they do not repeat but merely split signals sent through them).
Infrared - Electromagnetic waves whose frequency range is above that of microwaves, but below that of the visible spectrum.
Internet - A global network of networks used to exchange information using the TCP/IP protocol. It allows for electronic mail and the accessing ad retrieval of information from remote sources.
LAN (Local Area Network) - A network connecting computers in a relatively small area such as a building.
LocalTalk - Apple Corporation proprietary protocol that uses CSMA/CA media access scheme and supports transmissions at speeds of 230 Kbps (Kilobits per second).
MAN (Metropolitan Area Network) - A network connecting computers over a large geographical area, such as a city or school district.
Modem (Modulator/Demodulator) - Devices that convert digital and analog signals. Modems allow computer data (digital) to be transmitted over voice-grade telephone lines (analog).
Multiplexer - A device that allows multiple logical signals to be transmitted simultaneously across a single physical channel.
Network Modem - A modem connected to a Local Area Network (LAN) that is accessible from any workstation on the network.
Network Interface Card (NIC) - A board that provides network communication capabilities to and from a computer.
Network Operating System (NOS) - Operating system designed to pass information and communicate between more than one computer. Examples include Linux/Unix and Windows Server.
Node - End point of a network connection. Nodes include any device attached to a network such as file servers, printers, or workstations.
PCMCIA - (later versions were PCMCIA2 and PC Card) An expansion slot found in many laptop computers. Largely replaced by USB in the 2000-2010 period.
Peer-to-Peer Network - A network in which resources and files are shared without a centralized management source.
Physical Topology - The physical layout of the network; how the cables are arranged; and how the computers are connected.
Protocol -A formal description of a set of rules and conventions that govern how devices on a network exchange information.
RAID (Redundant Array of Inexpensive Disks) - A configuration of multiple disks designed to preserve data after a disk casualty.
RAM (Random Access Memory) - The working memory of a computer where data and programs are temporarily stored. RAM only holds information when the computer is on.
Repeater - A device used in a network to strengthen a signal as it is passed along the network cable.
Router -A device that routes information between interconnected networks. It can select the best path to route a message, as well as translate information from one network to another. Many routers now contain firewalls. Home routers can contain firewall, router, switching (for cabled connections), and a wireless access point.
SCSI (Small Computer Serial Interface) - An interface controller that allows several peripherals to be connected to the same port on a computer.
Segment - Refers to a section of cable on a network. In Ethernet networks, two types of segments are defined. A populated or trunk segment is a network cable that has one or more nodes attached to it. A link segment is a cable that connects a computer to an interconnecting device, such as a repeater or concentrator, or connects a interconnecting device to another interconnecting device.
Sneaker-Net - Refers to a manual method of sharing files in which a file is copied from a computer to a floppy disk, transported to a second computer by a person physically walking (apparently wearing sneakers) to the second computer, and manually transferring the file from floppy disk to the second computer.
Speed of Data Transfer - The rate at which information travels through a network, usually measured in megabits per second.
Star Topology - LAN topology in which each node on a network is connected directly to a central network hub or concentrator.
Star-Wired Ring - Network topology that connects network devices (such as computers and printers) in a complete circle.
Switch - A "intelligent" type of hub, in that it sends packets only to the intended ports, rather than all computers on the network.
Tape Back-Up - A common server or network peripheral which allows copying data and programs from a computer system to magnetic tape. On tape, data is stored sequentially. When retrieving data, the tape is searched from the beginning of tape until the data is found.
Terminator - A device that provides electrical resistance at the end of a transmission line. Its function is to absorb signals on the line, thereby keeping them from bouncing back and being received again by the network.
Token - A special packet that contains data and acts as a messenger or carrier between each computer and device on a ring topology. Each computer must wait for the messenger to stop at its node before it can send data over the network.
Token Ring - A network protocol developed by IBM in which computers access the network through token-passing. Usually uses a star-wired ring topology.
Topology - There are two types of topology: physical and logical. The physical topology of a network refers to the configuration of cables, computers, and other peripherals. Logical topology is the method used to pass the information between workstations. Issues involving logical topologies are discussed on the Protocol chapter
Transceiver (Transmitter/Receiver) - A Device that receives and sends signals over a medium. In networks, it is generally used to allow for the connection between two different types of cable connectors, such as AUI and RJ-45.
Tree Topology - LAN topology similar to linear bus topology, except that tree networks can contain branches with multiple nodes.
Twisted Pair - Network cabling that consists of four pairs of wires that are manufactured with the wires twisted to certain specifications. Available in shielded and unshielded versions.
USB/ USB2 Port - A hardware interface for peripherals from keyboards to hard drives, widely used on all computers.
WAN (Wide Area Network) - A network connecting computers within very large areas, such as states, countries, and the world.
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