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| A+ Certification |
A certification program from the CompTIA (Computer Technology Industry Association) designed to measure competence in basic computer repair and aimed at the computer technician. CeA certification program from the CompTIA (Computer Technology Industry Association) designed to measure competence in basic computer repair and aimed at the computer technician. Certification requires passing two tests: a core exam to test general knowledge of PCs, including configuration, installation and upgrading, diagnosis, repair, maintenance, customer interaction, and safety, and at least one specialty exam that tests operating system knowledge.
| A Record (Address record or Host record) |
An entry record in the DNS database that maps the hostname of a computer with its IP address.
| AA |
Acronym for “Auto Answer”.
| AAL |
See ATM Adaptation Layer.
| AAL1 |
ATM Adaptation Layer 1. One of four AALs recommended by the ITU-T, it is used for connection-oriented, time-sensitive services that need constant bit rates, such as isochronous traffic and uncompressed video. See also ATM Adaptation Layer.
| AAL2 |
ATM Adaptation Layer 2. One of four AALs recommended by the ITU-T, it is used for connection-oriented services that support a variable bit rate, such as voice traffic. See also
| AAL3/4 |
ATM Adaptation Layer 3/4. One of four AALs (a product of two initially distinct layers) recommended by the ITU-T, supporting both connectionless and connection-oriented links. Its primary use is in sending SMDS packets over ATM networks. See also ATM Adaptation Layer.
| AAL5 |
ATM Adaptation Layer 5. One of four AALs recommended by the ITU-T, it is used to support connection-oriented VBR services primarily to transfer classical IP over ATM and LANE traffic. This least complex of the AAL recommendations uses SEAL, offering lower bandwidth costs and simpler processing requirements but also providing reduced bandwidth and error-recovery capacities. See also ATM Adaptation Layer.
| AARP |
See AppleTalk Address Resolution Protocol.
| AARP Probe Packets |
Packets sent by the AARP to determine whether a given node ID is being used by another node in a nonextended AppleTalk network. If the node ID is not in use, the sending node approPackets sent by the AARP to determine whether a given node ID is being used by another node in a nonextended AppleTalk network. If the node ID is not in use, the sending node appropriates that node’s ID. If the node is in use, the sending node will select a different ID and then send out more AARP probe packets. See also AppleTalk Address Resolution Protocol.
| AASE |
See Associate Accredited Systems Engineer.
| a-b box |
A switching box that allows two or more computers to share a peripheral device such as a printer. It can be switched manually or through software.
| A+B Signaling |
A type of in-band signaling used in T1 transmission; one bit from each of the 24 subchannels in every sixth frame is used to carry dialing and other control information. A+B signaling reduces the T1 bandwidth from 1.544 Mbps to 1.536 Mbps. See also T1.
| A/UX |
A version of the Unix operating system that runs on the Macintosh. A/UX is baased on the System V release 2 of Unix and includes a number of Apple features, such as support for the Macintosh Toolbox. This support allows applications running under A/UX to use the familiar Macintosh user interface. You need a Macintosh II with a Motorola 68020 or higher microprocessor and at least 4MB of memory to use A/UX. See also Unix.
| ABCP |
See Associate Business Continuity Professional.
| Abend |
Contraction of abnormal end. A message issued by an operating system when it detects a serious problem, such as a hardware failure or major software damage.
| ABI |
See Application Binary Interface.
| ABIOS |
Acronym for “Advanced Basic Input/Output System”.
| ABM |
See Asynchronous Balanced Mode.
| ABR |
See Available Bit Rate or Area Border Router.
| Abstract Syntax Notation One (ASN.1) |
An OSI language used to describe types of data that is independent of computer structures and depicting methods. Described by ISO International Standard 8824.
| AC |
Acronym for “Alternating Current”.
| Accelerated Graphics Port |
A type of expansion slot supported by Windows 2000. AGP is used by video cards and supports high-quality video and graphics performance.
| Access Control Entries (ACE) |
Each ACL contains ACEs that are the permissions that have been granted or denied to the users and groups listed in the ACL. See also Access Control List.
| Access Control List (ACL) |
A list of security identifiers contained by an object. Only the processes identified on the ACL with appropriate permissions can activate the services of that object. See also Object, Security Identifiers, and Permissions.
| Access Layer |
One of the layers in Cisco’s three-layer hierarchical model. The access layer provides users with access to the internetwork.
| Access Link |
A link used with switches and is only part of one Virtual LAN (VLAN). Trunk lines carry information from multiple VLANs.
| Access List |
A set of test conditions kept by routers that determines “interesting traffic” to and from the router for various services on the network.
| Access Method |
The manner in which network devices approach gaining access to the network itself.
| Access Policy |
The set of rules that define the protocols, sites, and content that users behind an ISA server are allowed to access.
| Access Permissions |
A network security model in which rights to access network resources are determined on a basis of security policies stored in a user-access database on a server. A user logs on to the network. After that user has been allowed onto the network, the network security system determines access privileges in accordance with the security policies stored in the user-access database.
| Access Server |
Also known as a “network access server,” it is a communications process connecting asynchronous devices to a LAN or WAN through network and terminal emulation software, providing synchronous or asynchronous routing of supported protocols.
| Access Tokens |
Objects containing the security identifier of a running process. A process started by another process inherits the starting process’s access token. The access token is checked against each object’s ACL to determine whether appropriate permissions are granted to perform any requested service. See also Access Control List, Access Control Entries, Permissions, Object, Security Identifiers, and Process.
| Accessibility Options |
Windows 2000 Professional features used to support users with limited sight, hearing, or mobility. Accessibility Options include special keyboard, sound, display, and mouse configurations.
| Accessibility Wizard |
A Windows 2000 Professional Wizard used to configure a computer based on the user’s vision, hearing, and mobility needs.
| Account Lockout |
Used to specify how many invalid logon attempts should be tolerated before a user account is locked out. Account lockout is set through User Manager for Domains. See also Security and User Manager for Domains.
| Account Lockout Policy |
A Windows 2000 and Windows Server 2003 policy used to specify how many invalid logon attempts should be tolerated before a user account is locked out. Account lockout policies are set through account policies.
| Account Policies |
Windows Server 2003 policies used to determine password and logon requirements. Account policies are set through the Microsoft Management Console (MMC) Local Computer Policy or Domain Controllers Policy snap-in. See also Microsoft Management Console (MMC).
| Accounts |
Containers for security identifiers, passwords, permissions, group associations, and preferences for each user of a system. The User Manager administers accounts. See also Security Identifiers, Preferences, Permissions, Password, and Groups.
| Accredited Systems Engineer |
Abbreviated ASE. A certification from Compaq designed to evaluate and recognize expertise in installing and administering Compaq workstations and servers running both Microsoft Windows 2000 and Novell NetWare network operating systems. See also Associate Accredited Systems Engineer.
| ACE |
See Access Control Entries.
| Acknowledgement |
Verification sent from one network device to another signifying that an event has occurred. May be abbreviated as ACK. See also Negative Acknowledgement.
| ACL |
See Access Control List (ACL).
| ACM |
Acronym for “Association of Computing Machinery”.
| ACPI |
See Advanced Configuration and Power Interface.
| ACR |
See Allowed Cell Rate.
| Active Caching |
ISA server automatically retrieves web content before it expires, thereby keeping the cached material fresh for users.
| Active Desktop |
A Windows 2000 feature that makes the Desktop look and work like a Web page.
| Active Directory |
A directory service available with the Windows 2000 Server and Windows Server 2003 platforms. The Active Directory stores information in a central database and allows users to have a single user account (called a domain user account or Active Directory user account) for the network. See also Domain User Account and Active Directory User Account.
| Active Directory Connector (ADC) |
The service that replicates information between the Exchange Server 5.5 directory and Active Directory. Replicated information includes mailboxes, custom recipients, and distribution lists. The ADC uses Connection Agreements to define individual configurations for replication. Two versions of the ADC exist; one for Windows 2000 and one for Exchange 2000.
| Active Directory Installation Wizard (DCPROMO) |
The tool that is used for promoting a Windows Server 2003 or 2000 Server computer to a domain controller. Using the Active Directory Installation Wizard, systems administrators can create trees and forests. See also Promotion.
| Active Directory-Integrated (ADI) Zone |
A way of storing information for DNS zones within the Active Directory tree under the domain object container. Each Directory-Integrated zone is stored in a dnsZone container object identified by the name you choose for the zone when creating it.
| Active Directory Replication |
The process of synchronizing the data in the Active Directory database across all Active Directory servers. Uses a multimaster replication model. Only relevant changes are propagated. See also Multimaster Replication Model, Full Zone Transfers, Incremental Zone Transfers, Replication, Intersite and Replication, Intrasite.
| Active Directory Services Interfaces (ADSI) |
A directory service abstraction interface that allows programming languages that are compatible with the Component Object Model (COM), such as Visual Basic, VBScript, JavaScript, C, and C++ to make common directory calls to an underlying directory service. ADSI providers include Lightweight Directory Access Protocol (LDAP), NDS, Bindery, and Windows NT (SAM). Programmers and system administrators normally use ADSI to automate or script the bulk manipulation of directory entries.
| Active Directory User Account |
A user account that is stored in the Windows 2000 Server or Windows Server 2003 Active Directory’s central database. An Active Directory user account can provide a user with a single user account for a network. Also called a domain user account. See also Domain User Account.
| Active Directory Users and Computers (ADUC) |
On Windows 2000 Server or Windows Server 2003 domain controllers, the main tool used for managing the Active Directory users, groups, and computers. See also Domain Controller and Active Directory.
| Active Hub |
A hub that amplifies transmission signals and sends them to all the computers connected to it. This type of hub is often called a multiport repeater.
| Active Monitor |
The mechanism used to manage a Token Ring. The network node with the highest MAC address on the ring becomes the active monitor and is responsible for management tasks such as preventing loops and ensuring tokens are not lost.
| ActiveX |
The set of Microsoft protocols that specifies how software components can communicate with each other through the use of objects.
| ActiveX Data Objects (ADO) |
A COM (Component Object Model) object set created by Microsoft intended to replace all other database access object models in future releases of Microsoft products. ADO is a very robust object model in that it defines a core set of functions and allows extensions to be built into the model to support the individual features of certain types of databases. It is specifically designed to access OLE-DB data sources.
| AD |
See Active Directory.
| Adapter |
Any hardware device that allows communications to occur through physically dissimilar systems. This term usually refers to peripheral cards permanently mounted inside computers that provide an interface from the computer’s bus to another media such as a hard disk or a network. See also Network Interface Card and Small Computer Systems Interface.
| AD Connector |
A software component that allows synchronization between dissimilar directory services.
| ADCs |
Acronym for “Analog-to-Digital Converters”.
| Add Or Remove Programs |
Control Panel applet that allows for installing and uninstalling software applications and components of the Windows 2000 and Windows Server 2003 operating systems.
| Address |
In TCP/IP, an IP address is a 32-bit numeric identifier assigned to a node. The address has two parts, one for the network identifier and the other for the node identifier. All nodes on the same network must share the network address and have a unique node address. For networks connected to the Internet, network addresses are assigned by the Internet Activities Board (IAB). Addresses also include IPX addresses – the internal network number and external network number – and the MAC (Media Access Control) address assigned to each network card or device.
| Address Encapsulation |
Placing a sender’s native Exchange address in the form of a valid SMTP address. The encapsulated address is placed in the FROM field of the message.
| Address Learning |
Used with transparent bridges to learn the hardware addresses of all devices on an internetwork. The switch then filters the network with the known hardware (MAC) addresses.
| Address Mapping |
By translating network addresses from one format to another, this methodology permits different protocols to operate interchangeably.
| Address Mask |
A bit combination descriptor identifying which portion of an address refers to the network or subnet and which part refers to the host. Sometimes simply called the mask. See also Subnet Mask.
| Address Pool |
The range of IP addresses that the DHCP server can actually assign.
| Address Resolution |
The process used for resolving differences between computer addressing schemes. Address resolution typically defines a method for tracing Network layer (Layer 3) addresses to Data-Link layer (Layer 2) addresses. See also Address Mapping.
| Address Resolution Protocol (ARP) |
ARP determines the physical address used by the device containing the IP address. ARP maintains tables of address resolution data and can broadcast packets to discover addresses on the network segment or use previously cached entries. See also Physical Layer and Internet Protocol.
| Address Space |
The set of remote addresses that can be reached through a particular connector. Each connector must have at least one entry in its address space.
| Address Space Scoping |
A property that restricts a connector to transferring messages sent from a specified scope. The scope can be the organization, a site, or the server location the connector resides within.
| Address Translation Gateway (ATG) |
The mechanism within Cisco DECnet routing software that enables routers to route multiple, independent DECnet networks and to establish a user-designated address translation for chosen nodes between networks.
| Addressing Component |
A portion of the Internet Connection Sharing or Network Address Translation services that assigns IP addresses to clients; takes the place of a DHCP server.
| Adjacency |
The relationship made between defined neighboring routers and end nodes, using a common media segment, to exchange routing information.
| Administration Group |
A collection of Exchange 2000 servers that can be administered as a single unit. An administration group can include zero or more policies, routing groups, public folder trees, monitors, servers, conferencing servers, and chat networks. When security settings (permissions) are applied to an administration group, all child objects in the DS tree inherit the same Access Control Lists (ACLs) as the administration group node. Note that an administration group does not define the routing topology for messages; this is handled by routing groups.
| Administrative Distance |
A number between 0 and 225 that expresses the value of trustworthiness of a routing information source. The lower the number, the higher the integrity rating.
| Administrative Templates |
Templates that specify additional options that can be set using the Group Policy Editor tool.
| Administrative Tools |
Program group on Windows NT servers that contain utilities such as User Manager for Domains, Server Manager, Disk Administrator, Performance Monitor, and Network Monitor. See also User Manager for Domains, Server Manager, Disk Administrator, Performance Monitor, and Network Monitor.
| Administrative Weight |
A value designated by a network administrator to rate the preference given to a network link. It is one of four link metrics exchanged by PTSPs to test ATM network resource availability.
| Administrator Account |
A special user account in Windows NT and higher that has the ultimate set of security permissions and can assign any permission to any user or group. The Administrator account is used to correct security problems. See also Permissions.
| Administrators |
Users who are part of the Administrators group. This group has the ultimate set of security permissions. See also Administrator Account, Permissions, and Groups.
| Administrators Group |
A Windows 2000 built-in group that consists of Administrator accounts. See also Administrator Account.
| ADSI |
See Active Directory Services Interface (ADSI).
| ADSU |
See ATM Data Service Unit.
| Advanced Configuration and Power Interface (ACPI) |
A specification that controls the amount of power given to each device attached to the computer. With ACPI, the operating system can turn off peripheral devices when they are not in use.
| Advanced Power Management (APM) |
A Windows 2000 feature designed to reduce the power consumption of a computer, which is especially important for laptops that are running on battery power.
| Advanced Research Projects Agency Network (ARPANET) |
A packet-switched network developed in the early 1970s. The “father” of today’s Internet. ARPANET was decommissioned in June 1990.
| Advertising |
The process whereby routing or service updates are transmitted at given intervals, allowing other routers on the network to maintain a record of viable routes.
| AEP |
See AppleTalk Echo Protocol.
| Affinity |
See Group Affinity.
| AFI |
See Authority and Format Identifier.
| AFP |
See AppleTalk Filing Protocol.
| Age Limit |
A property that specifies the length of time a unit of data may remain in its container (e.g., public folder).
| Agents |
In the client/server model, the part of the system that performs information preparation and exchange on behalf of a client or server application.
| AGP |
See Accelerated Graphics Port.
| AH |
See Authentication Header.
| AIA |
See Authority Information Access Point.
| AIP |
See ATM Interface Processor.
| Alert |
1.) A mechanism that tells SQL Server which error codes to look for in the Windows NT Application log, and what action to take if an event is found. Alerts can be based on a severity level, an error code, and the database in which the error occurred. An alert can notify an operator and/or perform a task. Alerts are stored in the Msdb database.
2.) A warning trigger that is activated by predefined conditions such as cache initialization failures, service shutdowns, or even intrusion detections. Alerts can be configured to log an entry to the event log or even send an e-mail message or page to you.
| Algorithm |
A sequence of steps needed to solve logical or mathematical problems. Certain cryptographic algorithms are used to encrypt or decrypt data files and messages and to sign documents digitally.
| Alias |
A mechanism that allows a login to access a database under the username assigned to another login. The alias is stored in the sysalternates system table of the database. Each login can have either a username in a database or an alias, but not both. An alias can be used to consolidate permissions under special user accounts, such as DBO. These have been kept in SQL Server 7 for backward-compatibility. SQL 7 uses the concept of roles, which replaces the need for an alias.
| Alignment Error |
An error occurring in Ethernet networks, in which a received frame has extra bits; that is, a number not divisible by eight. Alignment errors are generally the result of frame damage caused by collisions.
| Allocation Unit |
In SQL Server, a structure designed to provide a method of keeping track of which pages are allocated to which objects. When a database is created, it is divided into allocation units. When an allocation unit is created, it is built from 32 extents. The very first page of the first extent of the allocation unit is called the allocation page. The allocation page is responsible for keeping track of every extent in the allocation unit. Allocation units affect the size of the database. Databases must be created and maintained in full allocation-unit intervals, which are 8 extents, or 512KB in size.
| Allowed Cell Rate (ACR) |
A designation defined by the ATM Forum for managing ATM traffic. Dynamically controlled using congestion control measures, the ACR varies between the minimum cell rate (MCR) and the peak cell rate (PCR). See also Minimum Cell Rate and Peak Cell Rate.
| All-Routes Explorer Packet |
An explorer packet that can move across an entire SRB network, tracing all possible paths to a given destination. Also known as an all-rings explorer packet. See also Explorer Packet, Local Explorer Packet and Spanning Explorer Packet.
| AltaVista |
A World Wide Web indexing service operated by Digital Equipment Corporation. This service allows you to query nearly the entire set of World Wide Web pages by key word and returns a best-match-first result. This site is located at www.altavista.digital.com.
| Alternate Mark Inversion (AMI) |
A line-code type on T1 and E1 circuits that shows zeros as “01″ during each bit cell, and ones as “11″ or “00″, alternately, during each bit cell. The sending device must maintain ones density in AMI but not independently of the data stream. Also known as binary-coded, alternate mark inversion. See also Ones Density.
| AM |
See Amplitude Modulation.
| AMD |
Acronym for Advanced Micro Devices”.
| American National Standards Institute (ANSI) |
The organization of corporate, government, and other volunteer members that coordinates standards-related activities, approves U.S. national standards, and develops U.S. positions in international standards organizations. ANSI assists in the creation of international and U.S. standards in disciplines such as communications, networking, and a variety of technical fields. It publishes over 13,000 standards, for engineered products and technologies ranging from screw threads to networking protocols. ANSI is a member of the IEC and ISO.
| American Standard Code for Information Interchange (ASCII) |
A standard coding scheme that assigns numeric values to letters, numbers, punctuation characters, and control characters to achieve compatibility among different computers and peripheral devices. In ASCII, each character is represented by a unique integer value in the range 0 through 255. See also ASCII Extended Character Set, ASCII File, ASCII Standard Character Set, Double-Byte Character Set, Extended Binary Coded Decimal Interchange Code, and Unicode.
| AMI |
See Alternate Mark Inversion.
| Amplifier |
A type of repeater that simply amplifies the entire incoming signal. Unfortunately, it amplifies both the signal and the noise.
| Amplitude |
In communications, the distance between the highest and lowest points in a wave. The amplitude controls the strength, or volume, of the signal.
| Amplitude Modulation (AM) |
A modulation method that represents information by varying the amplitude of the carrier signal. See also Modulation.
| Analog Data |
Data that has an infinite number of possible states, rather than the simple 1′s and 0′s of a digital signal. Audio, video, and voice telephone signals, for example, can all be represented using analog signals.
| Analog Signal |
Analog signals constantly vary in one or more values, and these changes in values can be used to represent data. Analog waveforms frequently take the form of sine waves.
| Analog Transmission |
Signal messaging whereby information is represented by various combinations of signal amplitude, frequency, and phase.
| Anonymous Access |
Accessing a server without logging in with a Windows NT or other type of user account.
| Anonymous Logon Group |
A Windows 2000 special group that includes users who access the computer through anonymous logons. Anonymous logons occur when users gain access through special accounts, such as the IUSR_computername and TsInternetUser user accounts.
| ANSI |
See American National Standards Institute.
| Answer File |
An automated installation script used to respond to configuration prompts that normally occur in a Windows 2000 Professional installation. Administrators can create Windows 2000 answer files with the Setup Manager utility.
| Anti-antivirus Virus |
Anti-antivirus viruses attack, disable or infect specific anti-virus software.
| Anti-Virus Software |
Anti-virus software scans a computer’s memory and disk drives for viruses. If it finds a virus, the application informs the user and may clean, delete or quarantine any files, directories or disks affected by the malicious code.
| Antivirus Virus |
Antivirus viruses specifically look for and remove other viruses.
| Anycast |
An ATM address that can be shared by more than one end system, allowing requests to be routed to a node that provides a particular service.
| APCUG |
Acronym for “Association of PC Users Groups”.
| APM |
See Advanced Power Management.
| APPEND |
Allows programs to open data files in specified directories as if they were in the current directory.
| Applet |
Any miniature application transported over the Internet, especially as an enhancement to a Web page. Authors often embed applets within the HTML page as a foreign program type. Java applets are usually only allowed to access certain areas of the user’s system. Computer programmers often refer to this area as the sandbox.
| AppleTalk |
AppleTalk is the computing architecture developed by Apple Computer for the Macintosh family of personal computers. Although AppleTalk originally supported only Apple’s proprietary LocalTalk cabling system, the suite has been expanded to incorporate both Ethernet and token ring Physical layers. Within Microsoft operating systems, AppleTalk is only supported by Windows NT Server. See also Macintosh.
| AppleTalk Address Resolution Protocol (AARP) |
The protocol in an AppleTalk stack that maps data-link addresses to network addresses.
| AppleTalk Control Program (ATCP) |
The protocol for establishing and configuring AppleTalk over PPP, defined in RFC 1378. See also Point-to-Point Protocol.
| AppleTalk Echo Protocol (AEP) |
A test for connectivity between two AppleTalk nodes where one node sends a packet to another and receives an echo, or copy, in response.
| AppleTalk Filing Protocol (AFP) |
A Presentation-layer protocol, supporting AppleShare and Mac OS File Sharing, that permits users to share files and applications on a server.
| AppleTalk Remote Access (ARA) |
A protocol for Macintosh users establishing their access to resources and data from a remote AppleTalk location.
| AppleTalk Session Protocol (ASP) |
A protocol employing ATP to establish, maintain, and tear down sessions, as well as sequence requests. See also AppleTalk Transaction Protocol.
| AppleTalk Transaction Protocol (ATP) |
A transport-level protocol that enables reliable transactions between two sockets, where one requests the other to perform a given task and to report the results. ATP fastens the request and response together, assuring a loss-free exchange of request-response pairs.
| AppleTalk Update-Based Routing Protocol (AURP) |
A technique for encapsulating AppleTalk traffic in the header of a foreign protocol that allows the connection of at least two noncontiguous AppleTalk internetworks through a foreign network (such as TCP/IP) to create an AppleTalk WAN. The connection made is called an AURP tunnel. By exchanging routing information between exterior routers, the AURP maintains routing tables for the complete AppleTalk WAN. See also AURP Tunnel.
| Application |
Software (program) designed to carry out a certain activity, such as word processing.
| Application Assignment Scripts |
Script files that specify which applications are assigned to users of the Active Directory.
| Application Binary Interface |
Abbreviated ABI. A specification that aims to ensure binary compatibility between applications running on the same family of processors or CPUs using Unix System V Release 4. Applications developed using ABI can run on hardware from different manufacturers without being recompiled; any system calls needed for specific hardware are maintained in libraries. The specification was originally developed by AT&T and Sun Microsystems and includes a test and verification suite used to determine if a system complies with the standard. See also Application Programming Interface.
| Application Data Partitions |
Portion of the Active Directory that is dedicated to application data and replicated along with the rest of the Active Directory database.
| Application Filters |
Allows for an added layer of security by providing application-specific filtering. Application filters examine the data stream, and not just the specific packet, looking for allowable content.
| Application Layer |
The layer of the OSI model that interfaces with User mode applications by providing high-level network services based upon lower-level network layers. Network file systems like named pipes are an example of Application layer software. See also Named Pipes, Open Systems Interconnect Model, and Application.
| Application Log |
A log that tracks events that are related to applications that are running on the computer. The Application log can be viewed in the Event Viewer utility. See also Event Viewer.
| Application Programming Interface (API) |
A collection of programming commands (frequently called interfaces) that can invoke the functions of a program. Other programs can use a program’s API to request services or communicate with that program. For example, Windows 95 contains an API referred to as the win32 API. For an application to request a service from Windows 95, it must issue that request using a win32 API.
| Application Server |
A server that provides some high-end application used by many different computers.
| Application Server Mode |
A Terminal Services mode that gives users remote access to applications running on the server. Using this mode, Terminal Services delivers the Windows 2000 Desktop environment to computers that might not otherwise be able to run Windows 2000 because of hardware or other limitations. See also Terminal
Services and Desktop.
| Application-Specific Integrated Circuits (ASICs) |
Used in layer-2 switches to make filtering decisions. The ASIC looks in the filter table of MAC addresses and determines which port the destination hardware address of a received hardware address is destined for. The frame will be allowed to traverse only that one segment. If the hardware address is unknown, the frame is forwarded out all ports.
| APW |
Acronym for “Add Printer Wizard”.
| ARA |
See AppleTalk Remote Access.
| Archie |
A program that helps Internet users find files. Participating Internet host computers download a listing of their files to Archie servers, which index these files. Users can then search this index and transfer these files using FTP. Archie functions as an archive search utility, hence its name.
| Architecture |
The description of the components of a product or system, what they are, what they do, and how they relate to each other.
| ARCNet |
Acronym for “Attached Resource Computer Network”. An older architecture that physically followed a physical bus or star topology and used a form of token passing to transmit data.
| Area |
A logical, rather than physical, set of segments (based on either CLNS, DECnet, or OSPF) along with their attached devices. Areas are commonly connected to others using routers to create a single autonomous system. See also Autonomous System.
| Area Border Router |
An OSPF router that is located on the border of one or more OSPF areas. ABRs are used to connect OSPF areas to the OSPF backbone area.
| Area Router |
An OSPF router that is restricted to routing traffic between machines inside a single area.
| ARM |
See Asynchronous Response Mode.
| Armored Virus |
An armored virus tries to prevent analysts from examining its code. The virus may use various methods to make tracing, disassembling and reverse engineering its code more difficult.
| ARP |
See Address Resolution Protocol.
| ARPANET |
See Advanced Research Projects Agency Network.
| Article |
The basic unit of replication. An article is one or more columns and rows of a table.
| ASBR |
See Autonomous System Boundary Router.
| ASCII |
See American Standard Code for Information Interchange.
| ASCII Extended Character Set |
The second group of characters, from 128 through 255, in the ASCII character set. The extended ASCII character set is assigned variable sets of characters by computer hardware manufacturers and software developers, and it is not necessarily compatible between different computers. The IBM extended character set used in the PC includes mathematics symbols and characters from the PC line-drawing set. See also American Standard Code for Information Interchange, ASCII File, ASCII Standard Character Set, Double-Byte Character Set, Extended Binary Coded Decimal Interchange Code, and Unicode.
| ASCII File |
A file that contains only text characters from the ASCII character set. An ASCII file can include letters, numbers, and punctuation symbols, but does not contain any hidden text-formatting codes. Also known as a text file or an ASCII text file. See also American Standard Code for Information Interchange, ASCII Extended Character Set, ASCII Standard Character Set, and Binary File.
| ASCII Standard Character Set |
A character set that consists of the first 128 (from 0 through 127) ASCII characters. The values 0 through 31 are used for nonprinting control codes, and the range 32 through 127 isused to represent the letters of the alphabet and common punctuation symbols. The entire set from 0 through 127 is referred to as the standard ASCII character set. All computers that use ASCII can understand the standard ASCII character set. See also American Standard Code for Information Interchange, ASCII File, ASCII Extended Character Set, Double-Byte Character Set, Extended Binary Coded Decimal Interchange Code, and Unicode.
| ASCII Text File |
See ASCII File.
| ASICs |
See Application-Specific Integrated Circuits.
| ASMP |
See Asymmetrical Multiprocessing.
| ASN.1 |
See Abstract Syntax Notation One.
| ASP |
See AppleTalk Session Protocol.
| Assigned Applications |
Applications installed with Windows Installer packages. Assigned applications are automatically installed when the user selects the application on the Programs menu or by document invocation (by the document extension).
| Assigning |
The process by which applications are made available to computers and/or users.
| Associate Accredited Systems Engineer |
Abbreviated AASE. A certification from Compaq designed to evaluate and recognize basic knowledge of PC architecture and operations. An AASE may choose to specialize in Microsoft Windows 2000 or Novell NetWare operation. See also Accredited Systems Engineer.
| Associate Business Continuity Professional |
Abbreviated ABCP. A certification from Disaster Recovery Institute International (DRII) that covers basic information on business continuity planning and disaster recovery. See also Certified Business Continuity Professional and Master Business Continuity Professional.
| AST |
See Automatic Spanning Tree.
| Asymmetric Digital Subscriber Line |
One new type of broadband WAN connectivity that is being tested by the telephone companies. Available only since 1997, ADSL is a Physical layer standard of sending data across existing telephone wires. By using a special ADSL modem, users can receive data at rates over 8 Mbps and send data at rates of up to 640 Kbps.
| Asymmetric Encryption |
Uses one key to encrypt data and a different key to decrypt data. Asymmetric encryption is used in public key systems.
| Asymmetrical Multiprocessing |
A multiple processor architecture in which certain processors are designated to run certain threads or in which scheduling is not done on a fair-share basis. Asymmetrical multiprocessing is easier to implement than symmetrical multiprocessing, but does not scale well as processors are added. See also Microprocessor and Symmetrical Multiprocessing.
| Asynchronous Balanced Mode (ABM) |
When two stations can initiate a transmission, ABM is an HDLC (or one of its derived protocols) communication technology that supports peer-oriented, point-to-point communications between both stations.
| Asynchronous Transmission |
Digital signals sent without precise timing, usually with different frequencies and phase relationships. Asynchronous transmissions generally enclose individual characters in control bits (called start and stop bits) that show the beginning and end of each character. See also Isochronous Transmission and Synchronous Transmission.
| Asynchronous Modems |
Do not use a clocking mechanism to keep the sending and receiving devices synchronized. Instead, this type of transmission uses bit synchronization to synchronize the devices for each frame that is transmitted.
| Asynchronous Response Mode (ARM) |
An HDLC communication mode using one primary station and at least one additional station, in which transmission can be initiated from either the primary or one of the secondary units.
| Asynchronous Time-Division Multiplexing (ATDM) |
A technique for sending information, it differs from normal TDM in that the time slots are assigned when necessary rather than preassigned to certain transmitters.
| Asynchronous Transfer Mode (ATM) |
A high-bandwidth switching technology developed by the ITU Telecommunications Standards Sector (ITU-TSS). An organization called the ATM Forum is responsible for defining ATM implementation characteristics. ATM can be layered on other Physical layer technologies, such as Fiber Distributed Data Interface (FDDI) and SONET. See also Public Switched Telephone Network and Wide Area Network.
| ATA |
Acronym for “AT Attachment”.
| ATAPI |
Acronym for “ATA Packet Interface”.
| ATCP |
See AppleTalk Control Program.
| ATDM |
See Asynchronous Time-Division Multiplexing.
| ATDT |
Modem command – Dial Tone.
| ATG |
See Address Translation Gateway.
| ATH/ATHO |
Modem command – Hang Up.
| ATM |
See Asynchronous Transfer Mode.
| ATM Adaptation Layer (AAL) |
Abbreviated AAL. A service-dependent layer in Asynchronous Transfer Mode (ATM) that provides the protocol translation between ATM and other communications services involved in a transmission. AAL has several service types and classes of operation to handle different kinds of traffic, depending on how data is transmitted, the bandwidth required, and the types of connection involved. See also Convergence Sublayer and Segmentation and Reassembly Sublayer.
| ATM ARP Server |
A device that supplies logical subnets running classical IP over ATM with address-resolution services.
| ATM Data Service Unit (ADSU) |
The terminal adapter used to connect to an ATM network through an HSSI-compatible mechanism. See also Data Service Unit.
| ATM Endpoint |
The initiating or terminating connection in an ATM network. ATM endpoints include servers, workstations, ATM-to-LAN switches, and ATM routers.
| ATM Forum |
The international organization founded jointly by Northern Telecom, Sprint, Cisco Systems, and NET/ADAPTIVE in 1991 to develop and promote standards-based implementation agreements for ATM technology. The ATM Forum broadens official standards developed by ANSI and ITU-T and creates implementation agreements before official standards are published.
| ATM Interface Processor (AIP) |
Supporting AAL3/4 and AAL5, this interface for Cisco 7000 series routers minimizes performance bottlenecks at the UNI. See also AAL3/4 and AAL5.
| ATM Layer |
The sublayer of the Data Link layer in an ATM network that is service independent. To create standard 53-byte ATM cells, the ATM layer receives 48-byte segments from the AAL and attaches a 5-byte header to each. These cells are then sent to the Physical layer for transmission across the physical medium. See also ATM Adaptation Layer.
| ATMM |
See ATM Management.
| ATM Management (ATMM) |
A procedure that runs on ATM switches, managing rate enforcement and VCI translation. See also Asynchronous Transfer Mode.
| ATM User-User Connection |
A connection made by the ATM layer to supply communication between at least two ATM service users, such as ATMM processes. These communications can be uni- or bidirectional, using one or two VCCs, respectively. See also ATM Layer and ATM Management.
| ATP |
See AppleTalk Transaction Protocol.
| Attachment User Interface (AUI) |
AUI specifies how a transceiver is attached to an Ethernet device. See also Digital Intel Xerox (DIX).
| Attack |
An attempt to subvert or bypass a system’s security. Attacks may be passive or active. Active attacks attempt to alter or destroy data. Passive attacks try to intercept or read data without changing it. See also Brute Force Attack, Denial of Service Attack, Hijacking, Password Attacks, and Password Sniffing.
| Attenuation |
The degradation of a signal, caused by traveling too far of a distance.
| ATTRIB |
Displays or changes file attributes.
| Attribute |
1.) A characteristic of an object. Attributes of a mailbox include display name, primary Windows NT account, and storage limits. The terms attribute and property are synonymous.
2.) Each object within the AD structure represents a record in the AD database. The fields of each record are known as attributes.
| Attribute Definition Object |
An object within the schema that holds a description of an attribute.
| ATZ |
Modem command – Reset Modem.
| AT&F |
Modem command – Reset Modem to Factory Settings.
| Auditing |
The process of creating a database that records particular events that occur on your network.
| Audit Policy |
Audit policy determines which user events you want to track for security reasons. Audit policy can track the success or failure of specified security events; it is set in the User Manager. See also Security and User Manager for Domains.
| AUI |
Acronym for “Auxiliary Unit Interface” (15-pin Network Connector).
| AURP |
See AppleTalk Update-Based Routing Protocol.
| AURP Tunnel |
A connection made in an AURP WAN that acts as a single, virtual link between AppleTalk internetworks separated physically by a foreign network such as a TCP/IP network. See also AppleTalk Update-
Based Routing Protocol.
| Authenticated Users Group |
A Windows 2000 special group that includes users who access the Windows 2000 operating system through a valid username and password.
| Authentication |
The process required to log on to a computer locally or to Active Directory. Authentication requires a valid username and password that exists in the local accounts database or in Active Directory. A ticket will be created if the information presented matches the account in the database.
| Authentication Header (AH) |
Used to digitally sign the entire contents of each packet.
| Authoritative Restore |
Specifies that the contents of a certain portion of the Active Directory on a domain controller should override any changes on other domain controllers, regardless of their sequence numbers. An authoritative restore is used to restore the contents of the Active Directory to a previous point in time. See Restore, Authoritative.
| Authority and Format Identifier (AFI) |
The part of an NSAP ATM address that delineates the type and format of the IDI section of an ATM address.
| Authority Information Access Point (AIA) |
A list of locations where users can get the CAs certificate and authentication information.
| Authority Zone |
A portion of the domain-name tree associated with DNS for which one name server is the authority. See also Domain Name Service.
| AutoAssistants |
A feature of a mailbox or public folder that can automatically carry out actions based on rules the user defines.
| Autodiscovery |
The process by which a web browser can locate an ISA server on a network without any user input. Autodiscovery makes use of configuration settings enabled in either DNS or DHCP.
| Auto Duplex |
A setting on layer-1 and -2 devices that sets the duplex of a switch or hub port automatically.
| AUTOEXEC.BAT |
A batch file containing commands which are automatically executed on booting up the system.
| Automated Installation |
The process of installing Windows 2000 using an unattended setup method such as Remote Installation Services (RIS), unattended installation, or disk images.
| Automated System Recovery (ASR) |
A process used for system recovery in the event of system failure. It is a two-part process that utilizes a backup component and a restore component. The system information that is backed up by ASR includes System State data, system services, and disk configuration information (information about basic and dynamic disks and the file signature associated with each disk).
| Automatic Call Reconnect |
A function that enables automatic call rerouting away from a failed trunk line.
| Automatic Recovery |
A feature built into SQL Server that insures that a database is brought up to date when the server is first started. Transactions completed since the last checkpoint process are rolled forward and put into the database, while partially completed transactions are rolled back or removed from the database. Every time SQL Server is restarted, SQL Server runs its automatic recovery feature.
| Automatic Spanning Tree (AST) |
A function that supplies one path for spanning explorer frames traveling from one node in the network to another, supporting the automatic resolution of spanning trees in SRB networks. AST is based on the IEEE 802.1 standard. See also IEEE 802.1 and Source-Route Bridging.
| Automatic Update |
Used to extend the functionality of Windows Update by automating the process of updating critical files. With Automatic Update, you can specify whether you want updates to be automatically downloaded and installed or whether you just want to be notified when updates are available.
| Autonomous Confederation |
A collection of self-governed systems that depend more on their own network accessibility and routing information than on information received from other systems or groups.
| Autonomous Switching |
The ability of Cisco routers to process packets more quickly by using the ciscoBus to switch packets independently of the system processor.
| Autonomous System (AS) |
A group of networks under mutual administration that share the same routing methodology. Autonomous systems are subdivided by areas and must be assigned an individual 16-bit number by the IANA. See also Area.
| Autonomous System Boundary Router (ASBR) |
An area border router placed between an OSPF autonomous system and a non-OSPF network that operates both OSPF and an additional routing protocol, such as RIP. ASBRs must be located in a non-stub OSPF area. See also Area Border Router, Non-Stub Area and Open Shortest Path First.
| Autoreconfiguration |
A procedure executed by nodes within the failure domain of a Token Ring, wherein nodes automatically perform diagnostics, trying to reconfigure the network around failed areas.
| Auto-Static Update Mode |
RIP update mode in which the RIP router only broadcasts the contents of its routing table when a peer router asks for it. See also Periodic Update Mode.
| Auxiliary Class |
An object class that is an extension of an existing class.
| Auxiliary Port |
The console port on the back of Cisco routers that allows you to dial the router and make console configuration settings.
| Availability |
The ability to provide end users with access to a service for a high percentage of time while reducing unscheduled outages. Availability can be expressed numerically as a percentage of the time that a service is available for use, using this formula: Percentage of availability = (total time – downtime)/total time * 100.
| Available Bandwidth |
The amount of additional traffic that a network segment can handle once current traffic has been taken into account (total bandwidth – used bandwidth = available bandwidth).
| Available Bit Rate |
A Type 3 or Type 4 Asynchronous Transfer Mode Adaptation Layer (AAL) service designed for non-time-critical applications such as LAN emulation and LAN internetworking. See also Constant Bit Rate, Unspecified Bit Rate and Variable Bit Rate.
| Available Cell Rate (ACR) |
A measurement of the bandwidth in Asynchronous Transfer Mode (ATM) networks. The ACR value represents the number of ATM cells available or allowed per second for a specific quality of service (QoS) class. Available Cell Rate is also known as Allowed Cell Rate. See also Asynchronous Transfer Mode, Minimum Cell Rate, Peak Cell Rate and Sustainable Cell Rate.
| AWG |
Acronym for “American Wire Gauge”.
