Glossary of Terms

10Base5 (10 Mbps, baseband, 500 meter): one of several physical media specified by 802.3 for use in an Ethernet local area network LAN); consists of Thickwire coaxial cable with a maximum segment length of 500 meters

10Base2 (10 Mbps, baseband, 185 meter): one of several physical media specified by IEEE 802.3 for use in an Ethernet local area network LAN); consists of Thickwire coaxial cable with a maximum segment length of 185 meters

10BaseT (10 Mbps, baseband, unshielded twisted-pair): one of several physical media specified by IEEE 802.3 for use in an Ethernet local area network (LAN); is ordinary telephone twisted pair wire

100BaseT (100 Mbps, baseband, unshielded twisted-pair): one of several physical media specified by IEEE 802.3 for use in an Ethernet local area network (LAN); referred to as Fast Ethernet because of its higher transmission speed

10 GbE (10 Gigabit Ethernet): an IEEE 802.3 Ethernet local area network protocol with a data transfer rate of 10,000 Mb/s (10 Gb/s); disruptive technology that provides high-speed data exchange between storage networks using FC technology.

3G: third-generation cell phone technology designed for data transfer and streaming services, such as video.

4G: fourth-generation cell phone technology suite that will be fully based on TCP/IP; all voice communication will be packetized for transfer as data.

AAL (ATM adaptation layer): adapts PDUs passed down from higher layers onto ATM cells

Absorption: type of signal interference that relates to the ability of some objects to absorb radio and data waves and therefore reduce the distance, or possibly stop entirely, a transmission.

Access Control: the manner in which devices are granted or denied access to the resource in cases where two or more devices simultaneously attempt to use a shared resource (e.g., telecommunications circuit between two sites, specific printer).

Access Control List (ACL): the database that keeps track of and controls access to network services through assigned privileges for users and groups. Also called authorization profile.

Access Point (AP): a stand-alone hardware device or a computer with a wireless adaptor and software, which acts as a wireless communication hub. It enables wireless devices to connect to each other and to link wireless devices to the cabled portion of the network.

Active Hub: allows multiple devices to be wired to a central location to share the same media and regenerate the signal; also referred to as multiport repeater.

Address Resolution: a process used to associate network addresses with media access control addresses.

ADSL (asymmetric digital subscriber line): typical form of xDSL telephone companies offer to residences; digital service designed to provide high data

AES (advanced encryption standard): popular encryption used primarily for Wi-Fi systems; considered to be a very secure encryption system and is used for some government data.

Agent: a software tool used to collect information about a device and make that information available to a network management system. Agents operate in managed devices on the network (e.g., hubs, switches, servers, stations).

AGP (accelerated or advanced graphics port): a highspeed, point-to-point channel for attaching a graphics card to a computer's motherboard, primarily to assist in the acceleration of 3D computer graphics.

ALU (arithmetic logic unit): a digital circuit that calculates an arithmetic operation (e.g., addition, subtraction) and logic operations between two numbers; the fundamental building block of the Central Processing Unit (CPU) or a computer.

AM (amplitude modulation): a technique used for transmitting information via a radio carrier wave by altering the power (amplitude).

Amplitude: height of the wave at any point in the wave.

Analog Signal: signal that uses continuous physical variables (e.g., amplitude or frequency variations) to transmit information; is analogous to the source transmission, such as a human voice; as the voice changes in tone and volume the waves change as well.

ANSI (American National Standards Institute): a voluntary organization that coordinates the development and use of consensus standards in the United States and represents the needs and views of U.S. stakeholders in standardization forums around the globe.

Antenna: a conductive structure specifically designed to couple or radiate electromagnetic energy. In radio frequency systems, the antenna may be used to both transmit and receive electromagnetic energy.

API (application programming interface): prewritten functions or set of routines to call on underlying network services used to make software programming easier and less likely to have errors.

Application Layer: responsible for providing mechanisms that enable software applications on different systems to use the services of a network to exchange information; performs the functions of file transfer, e-mail, etc. (see OSI Model); also known as Layer 7.

Architecture: how a system is designed; includes how the components are connected to and operate with each other.

ARP: (address resolution protocol): network layer protocol provided with TCP/IP; used to map an IP
(internet protocol) address to a MAC (media access card) address.

ARPANET: (Advanced Research Projects Agency Network): developed by DARPA in 1983; Internet basis.

AS: (autonomous system): collection of IP networks under the control of a single entity.

ASCII: (American Standard Code for Information Interchange): relates a number from 0 to 255 in the binary (base 2) form to keyboard characters; 7-bit binary code created to allow compatibility among various types of computer equipment.

ASIC: (application-specific integrated circuit): an integrated circuit designed for a particular use (e.g., a chip designed solely to run a cell phone).

Asynchronous Communication: describes when devices, such as computers, rely on their own internal clocks; it provides connectivity to printers, modems, fax machines, etc.

Asynchronous Signaling: a form of signaling in which each data character is coded as a string of bits. The bits are separated by start character and stop character bits.

Asynchronous Transmission: a data transmission method that does not require a clock synchronization signal for maintaining data integrity. Transmission is characterized by individual characters, surrounded by start and stop bits.

ATM: (asynchronous transfer mode): high bandwidth, cell-switching technology; designed to carry many different types of information, including voice, video, image, data, and graphics; another form of STDM (statistical time division multiplexing).

Attenuation: the decrease in magnitude or the power loss of a signal that propagates between points, often expressed in decibels as the ratio of received signal to transmitted signal level; refers to loss in signal strength, due to resistance, absorption, capacitance or any characteristics of the medium.

AUI: (attachment unit interface): a 15-pin connection that provides a path between a node’s Ethernet
interface and the medium attachment unit (MAU); also known as a transceiver.

Authentication: security mechanism that verifies a user’s identity; consists of three factors: something you know, something you have, and something you are.

Authorization: process of establishing and enforcing network activities that are permitted for a given user.

AUTONEG (Autonegotiation): a feature that determines link options and optimal settings for a given
Ethernet connection. When AUTONEG is enabled, a network interface card or a switch port can determine the capabilities of the device at the far end of the link and select the best mode of operation.

Availability: in security terms, ensuring that the data can actually be used by, and only by, the users who need it; measure of network response time or absence of operating failure (downtime) during a given period of time.

B Channel (bearer channel): carries voice, video, image, or data traffic, depending upon the equipment and applications available.

Backbone: a facility (e.g., pathway, cable, conductors) between any of the following spaces: telecommunications rooms, telecommunications enclosures, common telecommunications rooms, floor-serving terminals, entrance facilities, equipment rooms, and common equipment rooms.

Backup: a copy of the data stored on a device. Backup Storage: a redundant storage mechanism
that provides the means to recover from primary storage failure and the corresponding loss of data; also referred to as disaster recovery.

Balanced Cable: two or more insulated pairs of wires—identical in composition, size, and length—
uniformly twisted together.

Balun: a balanced-to-unbalanced circuit-coupling device, used to convert from unbalanced to balanced transmission, and provides impedance matching for connecting twisted-pair to coaxial cable.

Bandwidth: range of frequencies available for signaling; information transport capacity of a medium, also called analog capacity; expressed in hertz.

Base 2 System: binary number system, only two discrete values (0 and 1) are possible and all numbers are a combination of these two characters; digital signals are numbers sent in the Base 2 system.

Base 10 System: the decimal numbering system. Baseband: describes signals and systems whose
range of frequencies is measured from 0 to a maximum bandwidth or highest signal frequency; sometimes used as a noun for a band of frequencies starting at 0.

Baseband signaling: method of signal transmission where the entire bandwidth of the medium is used to send a single signal. Contrast with broadband signaling.

Baselining: uses monitoring and reporting software to record network utilization and traffic patterns during smooth operation.

Batch File: MSDOS text file that contains one or more DOS commands; .BAT extension is used to identify a batch file.

BAUD: unit measuring the signaling speed of the data transmission device. BGP (border gateway protocol): an interautonomous system routing protocol; a network or group of networks under a common administration and with common routing policies. Bidirectional Signaling: signals that pass in opposite directions between two transmitters. In a twisted-pair cable, this may be on the same or different pairs.

Binary: simple numbering system that alternates between two states, a 1 and a 0.

Bit (b): contraction of the expression “binary digit”; smallest unit of data in a computer.
Bits Per Second (b/s or bps): common measure of data speed (transfer rate) of a device, system, or communications channel; also called bit rate.

Biometrics: security method that relies on physically verifying that you are who you say you are; examples include retinal scans, finger and palm prints.

BIOS (basic input/output system): the firmware code run by an IBM-compatible PC when first powered on, known as “booting up”; primary function is to prepare the machine so other software programs can load, execute, and assume control of the PC.

Blade Server: self-contained computer servers, designed for high density in a small footprint; “Noncore” components are removed for space, power and other considerations leaving the functional components to be considered a computer.

Blade System Server: enclosure that holds multiple Blade servers containing centralized power, cooling, networking, various interconnects and management services shared by the Blade servers.
Bootable Disk: a bootable disk contains the boot files of an operating system and is used to “boot” a
computer.

Bluetooth: low-speed wireless communication protocol used for short-range data transfer; allows
mobile phones, computers, and PDAs to be connected wirelessly over short ranges.

Bridge: a Layer 2 networking device used to connect separate local area network collision domains (or
network segments) to extend network reach or selectively isolate network traffic. Bridges restrict collision domains but forward broadcasts.

Broadband: A high-speed wide area network digital signal.

Broadband Signaling: the simultaneous transmission of multiple signals over a medium (e.g., video signals multiplexed into channels with a bandwidth of 6 MHz each).

Broadcast: a technique for sending data simultaneously to all devices attached to a network with a
single transmission.

Broadcast Domain: the span of a network as represented by the devices capable of receiving a Layer 2 frame or Layer 3 datagram addressed to all devices.

Broadcast Group: the group of devices receiving a broadcast transmission.

Broadcast Storm: a series of retransmitted broadcasts caused by uncontrolled duplication of the original message.

Browser Mode: a form of remote access where the remote station accesses LAN resources through a Web server on the LAN and obtains access to resources designed to operate in a Web browser environment.

BRI (basic rate interface): an integrated services digital network configuration, usually intended for the home and small enterprise (see also PRI).

Bricks and Clicks: business that existed pre-Internet that now uses e-commerce technology to sell on the Internet.

Bridge: interprets the LAN hardware adapter address contained in MAC and decide whether to filter or
forward the frame; does not change the frame in any way.

Browsers: client applications that access World Wide Web servers.

Buffer: a block of RAM or other temporary storage area in a networking device used to temporarily hold incoming data until it can be processed or transfered from one device to another.

Building Backbone: connects LANs within a building.

Burst Mode: a data transmission mode in which data is sent faster than normal.

Bus: electrical connection between any two components in a computer; electrical path used to transmit control, data and address signals.

Bus Topology: networking layout where electrical signals generated by a device connected anywhere on the bus are received by all other connected devices; all devices are connected along a single wire with two endpoints.

Byte (B): the standard size of data in a computer; 8-bits; also called an octet.

Cable Tester: troubleshooting tool that consists of a two-piece system with a tester on one end and a responder on the other; tool that tests each cabling wire for breaks plus ensures that they are wired properly.

Cabling System: a specific system of telecommunications cables, equipment/patch cords, connecting
hardware, and other components that is supplied as a single entity.