Glossary of Terms

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AAL

ATM Adaptation Layer: Provides for reliable segmentation and reassembly of user traffic into 48 octet payloads.

ABR

Available Bit Rate: A quality of service designed to support data, including a flow control mechanism to support congestion problems in the network.

access control

Software, hardware, and administrative policies and procedures that monitor host or network operation, identify users, verify security codes or password(s), and record access.

Access Control List (ACL)

The list of the services available on a network or host and users permitted to use each service. This is the usual way that access to services (or denial of access) is controlled in most networks and multi-user host security systems.

ack

See Acknowledgment.

acknowledgment (ack)

A type of message sent to show that another previous message arrived at its destination without error.

ACL

Acronym for Access Control List.

active hub

A device used to amplify transmission signals in certain network topologies. An active hub can be used to either add additional workstations to a network or to lengthen the cable distance between nodes, workstations, and/or file servers on a network.

active monitor

Token ring software that removes data packets that have not been picked up from the ring by its target station.

active star

A hub-based networking topology that regenerates signals in active hubs.

activity daemon

A process that keeps a list of active agent requests sent from the host (where the daemon is running). The daemon periodically queries the agents to make sure they are still servicing their requests.

AD

Acronym for Administrative Domain.

address

An identified name for a logical or physical item that can be used to connect to that item.

address mask

A bit mask used to identify which bits in an address (usually an IP address) are network significant, subnet significant, and host significant portions of the complete address. This mask is also known as the subnet mask because the subnetwork portion of the address can be determined by comparing the binary version of the mask to an IP address in that subnet. The mask will hold the same number of bits as the protocol address it references.

address resolution

A means for mapping logical addresses to media-specific physical addresses when both pertain to the same device. See also: ARP.

Address Resolution Protocol (ARP)

A protocol used to dynamically discover the low level physical network hardware address that corresponds to the higher level protocol address for a given host. ARP is limited to physical network systems that support broadcast packets that can be heard by all hosts on the network.

address space

A collection of addresses that form a unified collection (such as an internetwork) or the portion of a protocol header that contains an address.

address translation

The process of converting an external address into a useable standardized internal address and vice versa.

addressing authority

The group responsible for assigning addresses within a domain.

Administrative Domain (AD)

A group of hosts, routers, gateways and interconnecting networks, if more than one, managed by a single organization or administrative authority. Routing within an administrative domain is based on a consistent plan.

agent

(1) A network management term for the portion of an entity that responds to management requests and/or preprogrammed traps. (2) In the client-server model, the part of the system that prepares information and exchanges it for a client or server application.

Aggregated Purchasing

Online purchasing that aggregates demand and provides discounts through group buying power.

Agility Factor

Refers to a phenomenon known as "Internet time" where one month of elapsed time is equal to an entire year in the bricks-and-mortar world.

alias

A name, usually easy to remember, that is translated into (or is a translation of) another name that is usually difficult to remember.

allocation

A concept used in the transport layer protocols. It is the amount of traffic that may be outstanding, without acknowledgments, at one time; also called window, as in sliding window.

alternate route

A secondary communications path used to reach a destination if the primary path is unavailable.

alternate routing

A way of completing connections that uses another path when the previous circuit is unavailable, busy, or out of service.

alternate use

The ability to switch communications facilities from one type to another, i.e., voice to data, etc.

AME

ATM Management Entity

American National Standards Institute (ANSI)

A private organization that coordinates some U.S. standards setting. It also approves some U.S. standards that are often called ANSI standards. ANSI represents the United States to the International Standards Organization (ISO). See also: International Standards Organization.

American Standard Code for Information Interchange (ASCII)

A standard character set that typically assigns an 7-bit sequence to each letter, number, and selected control character. It is erroneously used now to refer to 8-bit, extended ASCII. The other major encoding standard is EBCDIC.

anonymous FTP

Anonymous File Transfer Protocol lets users retrieve documents, files, programs, and other data from other TCP/IP connected hosts without having to establish a user ID and password. The special user ID of "anonymous" and password of "guest" or the user's E-mail address lets that user bypass local security checks and have access to selected files on the remote host. See also: File Transfer Protocol.

ANSI

Acronym for American National Standards Institute.

Apple

Maker of AppleTalk and the Macintosh.

AppleShare

Program that lets different types of computers offer or use AppleTalk resources, like printing.

Applet

A computer program designed to be executed from within another application.

application

A program that performs a user function; synonymous with program.

application environment specification

A goal of the Open Software Foundation.

application layer

The top-most layer (Layer 7) in the OSI Reference Model providing such communication services as electronic mail and file transfer. It is generically defined as the top layer of a network protocol stack.

application process

A part of a distributed application running on a single host; synonymous with process.

application terminal

An object accessed by an application on a slave node. For example, a printer attached to a terminal server would be the application terminal for the print spooler.

architecture

The relationship of the physical parts of a computer or network that is typically labeled by that relationship. For example, the Motorola 68000 architecture.

area

A term used, particularly in OSPF, in the routing layer to describe a group of networked devices; it is similar to a subnet.

ARP

Acronym for Address Resolution Protocol. Address Resolution Protocol is used to determine an IP host?s layer 2 MAC address.

ARPA

Acronym for Advanced Research Projects Agency.

ARPANET

Acronym for Advanced Research Projects Agency Network.

AS

Acronym for Autonomous System.

ASCII

Acronym for American Standard Code for Information Interchange.

ASCII terminal

A terminal that uses ASCII. The name frequently given to asynchronous terminals; synonymous with dumb terminal or glass tube.

ASIC

Application Specific Integrated Circuit. A chip that is custom designed for a particular application.

assigned numbers

The codes (numbers in hexadecimal, decimal, and/or binary format) that are officially recognized and assigned as part of the Internet standards.

Assigned Numbers RFC

The RFC that documents the current values for several series of numbers used in network protocols. This RFC is updated periodically. Current information can be obtained from the Internet Assigned Numbers Authority (IANA).

asymmetric modem

A full duplex modem that simultaneously sends data at two different speeds; for example, data is transmitted at high speed and acknowledgments are received at low speeds.

async

Asynchronous; a data transmission method that sends one character at a time. Contrast with the synchronous methods, which send a packet of data and then resynchronize their clocks. Asynchronous also refers to commands, such as in a windowing environment, that may be sent without waiting for a response from the previous command.

asynchronous communication

Communication in which the spaces between bytes or packets can be unequal lengths without needing timing data or synchronization. Sometimes called asynchronous transmission:

asynchronous communications adapter

A hardware device or module that lets a host system use an asynchronous data stream to send data to a desired target.

asynchronous event

Events that occur asynchronously on a system so that the user cannot predict which one will happen next.

asynchronous gateway

A device that lets asynchronous devices attach directly to a network; the generic term for a terminal server.

asynchronous mode

An OSI model for virtual terminal operation in which either side may communicate at any time.

asynchronous modem

A modem that uses async for transmitting data. Such a modem does not require synchronization with the remote modem or with the attached device.

Asynchronous Transfer Mode (ATM)

A method for the dynamic allocation of bandwidth using a fixed-size packet (called a cell). ATM is also known as "fast packet" and is an emerging WAN and LAN standard.

ATM

Acronym for Asynchronous Transfer Mode.

auth

Authentication Service.

authenticate

The function of verifying the identity of a person or process.

authentication

(1) The verification of the identity of a person or process. (2) The code used to identity a person or process.





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b

Bit

B

Byte

B channel

Bearer channel. A basic component of ISDN interfaces. It can carry voice or data at 64 Kbps.

backbone

The main connectivity device of a distributed system. All systems that have connectivity to the backbone will connect to each other. This does not stop systems from setting up private arrangements with each other to bypass the backbone for reasons of cost, performance, or security.

backbone cable

A main cable run vertically (or horizontally) in a building to provide wire connectivity to separate areas in the building. It is not designed for direct system access.

backbone closet

Space provided in a building for terminating pairs of wire and for connecting the backbone cable to systems in that area.

bandwidth

Technically, the difference, in Hertz (Hz), between the highest and lowest frequencies of a transmission channel. Usually identifies the capacity or the amount of data that can be sent through a given circuit.

bang

A UNIX term for the exclamation point (!).

Bank Rate

A percentage of each sale that the bank charges for processing credit card transactions. Also known as a ?discount rate.?

banner

A screen or page of printout (usually at the beginning) that gives information about the network, server, or file being accessed or printed.

base memory

The beginning of a block of memory. A network interface board uses the base memory address as a buffer. This is the address where both the computer and the network interface board can leave information and signal the other to pick it up.

Basic Input/Output System (BIOS)

A set of programs, usually in firmware, that lets each computer's central processing unit communicate with printers, disks, keyboards, consoles, and other attached input and output devices.

Basic rate interface (BRI)

One of the two forms of ISDN. It offers 144 Kbps service that includes two 64 Kbps channels (for data, voice, or video) and one 16 Kbps channel for control information.

baud

A unit of signaling speed. The speed in baud is the number of discrete conditions or signal elements per second. If each signal event represents only one bit condition, then baud is the same as bits per second. Baud rarely equals bits per second.

baud rate

The rate at which data is transferred over an asynchronous RS-232 serial connection.

BDC

NT Backup Domain Controller

beacon

A token ring packet that signals a serious failure on the ring.

benchmark

A point of reference from which measurements can be made. It involves the use of typical problems for comparing performance, and is often used in determining which computer can best serve a particular application.

BGP4

Border Gateway Protocol Version 4 (BGP4) is a protocol that includes authenticated routing updates, CIDR, and supernetting which reduce the size of routing tables and introduce other internet addressing and routing efficiencies.

binary

Base 2. Also known as "bin". Decimal, or base 10 is the common numbering system used by people in everyday life. Computers internally use base 2 (binary), base 8 (octal) or base 16 (hexadecimal) and only convert numbers to base 10 for human consumption.