CA

See Certificate Authority.

Cable Modem

This device allows networks to interconnect through existing cable TV lines. Some areas that offer this service have a full duplex version that allows transmission rates of 4 to 10 Mbps. Other areas have cable standards in place that only allow the coaxial TV cable to receive data, relying upon an analog dial-up connection to be used to send data.

Cable Range

In an extended AppleTalk network, the range of numbers allotted for use by existing nodes on the network. The value of the cable range can be anywhere from a single to a sequence of several touching network numbers. Node addresses are determined by their cable range value.

CAC

See Connection Admission Control.

Cache

An area of memory reserved for data, which speeds up access to a disk.

Cache Array Routing Protocol (CARP)

Microsoft’s algorithm that allows multiple proxy servers configured in an array to distribute retrieved web objects across asingle logical cache. Through the use of CARP, client reMicrosoft’s algorithm that allows multiple proxy servers configured in an array to distribute retrieved web objects across asingle logical cache. Through the use of CARP, client requests for web objects can be directed to the appropriate server that contains the requested information.

Cache Schema

The copy of the AD schema that is stored in memory.

Caching

A speed-optimization technique that keeps a copy of the most recently used data in a fast, high-cost, low-capacity storage device rather than in the device on which the actual data resides. Caching assumes that recently used data is likely to be used again. Fetching data from the cache is faster than fetching data from the slower, larger storage device. Most caching algorithms also copy data that is most likely to be used next and perform write-back caching to further increase speed gains. See also Write-Back Caching and Write-Through Caching.

Caching-Only Servers

A type of DNS server that resolves names on behalf of clients and caches the results to speed up subsequent queries. Caching-only servers are not authoritative for a zone. They do not store standard primary or standard secondary zones. They do, however, help to reduce WAN traffic because they do not generate zone transfer traffic, and because cached queries reduce the amount of name resolution traffic that needs to cross the WAN. See DNS Server, Caching-Only.

CAD

Acronym for “Computer Aided Design”.

CAL

See Client Access License.

Call Admission Control

A device for managing of traffic in ATM networks, determining the possibility of a path containing adequate bandwidth for a requested VCC.

Call Priority

In circuit-switched systems, the defining priority given to each originating port; it specifies in which order calls will be reconnected. Additionally, call priority identifies which calls are allowed during a bandwidth reservation.

Call Set-Up Time

The length of time necessary to effect a switched call between DTE devices.

Campus Area Network (CAN)

A network that spans a campus.

Canonical Name

An object’s name using a notation that lists all container objects in the path to the object, starting from the top of the AD tree and working down.

Card

A removable printed-circuit board that is plugged into an expansion slot.

CARP

See Cache Array Routing Protocol.

Carrier

A frequency in a communications channel modulated to carry analog or digital signal information. For example, an FM radio transmitter modulates the frequency of a carrier signal, and the receiver processes the carrier signal to extract the analog information. An AM radio transmitter modulates the amplitude of a carrier signal.

Carrier Sense Multiple Access Collision Detect (CSMA/CD)

Different devices on a network may try to communicate at any one time, so access methods need to be established. Using the CSMA/CD access method, a device first checks that the cable is free from other carriers and then transmits, while continuing to monitor the presence of another carrier. If a collision is detected, the device stops transmitting and tries later. In a CSMA network with collision detection, all stations have the ability to sense traffic on the network.

Castanet

A collection of software-update tools from Marimba, Inc. that operate over the Internet. Based on Java technology, Castanet can automatically deliver software updates not only for Java programs, but also for those written in C, C++, and Visual Basic, and because only the updated content is downloaded, performance is optimized. For more information on Castanet, see www.marimba.com. See also Server Push.

Category

A grouping of applications that are available for installation by users through the Add/Remove Programs applet in the Control Panel. Categories are useful for managing large lists of available applications.

CAU

Acronym for “Controlled-Access Unit”.

CAV

Acronym for “Constant Angular Velocity”.

Cavity Virus

A cavity virus overwrites a part of its host file without increasing the length of the file while also preserving the host’s functionality.

CBCP

See Certified Business Continuity Professional.

CBE

See Certified Banyan Engineer.

CBIOS

Acronym for “Compatibility BIOS”.

CBR

See Constant Bit Rate.

CBS

See Certified Banyan Specialist.

CCD

Acronym for “Charged Coupled Device”.

CCITT

Acronym for “Comite Consultatif de Telephonie et de Telegraphie”.

CCP

See Certified Computing Professional.

CCS

Acronym for “Common Communication Support”.

CD

Displays the name of or changes the current directory.

CDA

See Certified Database Administrator.

CD-Based Image

A type of image configured on a Remote Installation Services (RIS) server. A CD-based image contains only the Windows operating system.

CDFS

See Compact Disk File System.

CD-I

Acronym for “Compact Disk – Interactive”.

CDIA

See Certified Document Imaging Architect.

CDP

See CRL Distribution Point and Cisco Discovery Protocol.

CDPD

Acronym for “Cellular Digital Packet Data”.

CD-R

Acronym for “Compact Disk – Recordable”.

CD-Recordable

Using CD-R, you can write to the disc only once; after that, the disc can only be read from and not written to. From a functional point of view, a CD-R and a CD-ROM are identical; you can read CD-R discs using almost any CD-ROM drive, although the processes that create the discs are slightly different. Low cost CD-R drives are available from several manufacturers, including Kao, Kodak, Mitsui, Phillips, Ricoh, Sony, TDK, 3M, and Verbatim. See also CD-ReWritable, Digital Video Disc, Magneto-Optical Storage, and WORM.

CD-ReWritable

A CD format that can be written to and erased as many as 1000 times. From a functional point of view, a CD-RW and a CD-ROM are identical, but not all CD-ROM drives can read CD-RW discs. Low cost CD-RW drives are available from several manufacturers, including Kodak, Mitsui, Phillips, and Sony. See also CD-Recordable, Digital Video Disc, Magneto-Optical Storage, and WORM.

CD-ROM

See Compact Disk-Read Only Memory.

CDVT

See Cell Delay Variation Tolerance.

Cell

In ATM networking, the basic unit of data for switching and multiplexing. Cells have a defined length of 53 bytes, including a 5-byte header that identifies the cell’s data stream and 48 bytes of payload. See also Cell Relay.

Cell Delay Variation Tolerance (CDVT)

A QoS parameter for traffic management in ATM networks specified when a connection is established. The allowable fluctuation levels for data samples taken by the PCR in CBR transmissions are determined by the CDVT. See also Constant Bit Rate and Peak Cell Rate.

Cell Error Ratio (CER)

The ratio in ATM of transmitted cells having errors to the total number of cells sent in a transmission within a certain span of time.

Cell Loss Priority (CLP)

The area in the ATM cell header that determines the likelihood of a cell being dropped during network congestion. Cells with CLP = 0 are considered insured traffic and are not apt to be dropped. Cells with CLP= 1 are considered best-effort traffic that may be dropped during congested episodes, delivering more resources to handle insured traffic.

Cell Loss Ratio (CLR)

The ratio of discarded cells to successfully delivered cells in ATM. CLR can be designated a QoS parameter when establishing a connection.

Cell Payload Scrambling

The method by which an ATM switch maintains framing on some medium-speed edge and trunk interfaces (T3 or E3 circuits). Cell payload scrambling rearranges the data portion of a cell to maintain the line synchronization with certain common bit patterns.

Cell Relay

A technology that uses small packets of fixed size, known as cells. Their fixed length enables cells to be processed and switched in hardware at high speeds, making this technology the foundation for ATM and other high-speed network protocols. See also Cell.

Cell Transfer Delay (CTD)

For a given connection in ATM, the time period between a cell exit event at the source user-network interface (UNI) and the corresponding cell entry event at the destination. The CTD between these points is the sum of the total inter-ATM transmission delay and the total ATM processing delay.

Centralized Computing

A form of computing where all the processing is done by one central computer.

Centralized Management

A management model in which all IT resources are managed by a small group of people in a single location.

Central Office (CO)

The local telephone company office where all loops in a certain area connect and where circuit switching of subscriber lines occurs.

Central Processing Unit (CPU)

The central processing unit of a computer. In microcomputers such as IBM PC-compatible machines, the CPU is the microprocessor. See also Microprocessor.

Centrex

A local exchange carrier service, providing local switching that resembles that of an on-site PBX. Centrex has no on-site switching capability. Therefore, all customer connections return to the CO. See also Central Office.

CER

See Cell Error Ratio.

Certificate

A digital attachment to an electronic message that is used for authentication purposes. One of the most common uses is to verify that the user sending a message is who they claim to be. Certificates can be acquired from a third-party Certificate Authority (CA), such as VeriSign or Equifax, or can be issued in-house by configuring your own CA using Microsoft’s Certificate Service.

Certificate Authority (CA)

The central authority that distributes, publishes, and validates security keys. Exchange Server can be configured to perform this role. See also Public Key and Private Key.

Certificate Hierarchy

Also known as a certificate chain, can contain a series of certification authorities (CAs) from inside and outside a single organization, organized in a hierarchical trust model.

Certificate Policy and Practice Statements

Outline how the CA and its certificates are to be used, the degree of trust that can be placed in these certificates, legal liabilities if the trust is broken, and so on.

Certificate Revocation List (CRL)

A list of certificates that have been revoked for some reason, such as expiration. Each CA builds and maintains it own CRL.

Certificate Store

A database of certificates that contains end user and server certificates and the CRL.  The certificates themselves may be stored in the local computer’s Registry, in Active Directory, or in a database file, but they all appear as a single, seamless store.

Certificate Trust List (CTL)

A certified list that lets PKI administrators tell PKI clients to trust certificates issued by a particular set of CAs. The CTL information is stored in Active Directory.

Certificates

The codes exchanged to allow for encrypted information interchange. Each party has its own certificate identifying (uniquely) the party sending or receiving information.

Certification Practices Statements (CPSs)

Statements that set forth the terms and conditions under which the CA will issue certificates. Most large commercial CAs (like VeriSign and GTE) include CPSs in their certificates.

Certified Application Developer for Developer/2000

A certification from Oracle consisting of a set of exams covering Structured Query Language, the creation of procedures using Oracle Procedure Builder, using Developer/2000, and managing the user interface.

Certified Banyan Engineer (CBE)

A premium certification from Banyan designed to evaluate technical knowledge of the Banyan VINES network operating system. A candidate must complete two required courses and pass two exams.

Certified Banyan Specialist (CBS)

A basic certification from Banyan designed to evaluate technical knowledge of the Banyan VINES network operating system. A candidate must complete one required course and pass three exams. An additional certification concentrates on the integration of Banyan’s StreetTalk onto Microsoft Windows 2000 servers; to complete this certification, you must first become a Microsoft Certified Professional.

Certified Business Continuity Professional

Abbreviated CBCP. A certification from Disaster Recovery Institute International (DRII) that covers intermediate information on business continuity planning and disaster recovery and associated work experience and board certification. See also Associate Business Continuity Professional and Master Business Continuity Professional.

Certified Computing Professional (CCP)

A certification from the Institute for Certification of Computing Professionals designed for experienced professionals with more than four years experience in a wide variety of computing and related tasks.

Certified Database Administrator (CDA)

1. A certification from Oracle that covers knowledge of Structured Query Language, administration of Oracle products, along with backup and recovery, and system performance tuning.
2. A certification from Sybase that covers designing, building, and supporting Sybase SQL Server databases. See also Certified Performance and Tuning Specialist.

Certified Document Imaging Architect (CDIA)

A certification from the Computer Technology Industry Association (CompTIA) that assesses skills in document management, including scanning and storing documents in digital form and using optical character recognition software.

Certified Information System Auditor (CISA)

A certification from the Information Systems Audit and Control Association (ISACA) that covers ethics, security, system organization and management, and system development, acquisition, and maintenance.

Certified Information Systems Security Professional (CISSP)

A certification from the International Information System Security Certification Consortium designed for system security experts with at least three years of practical experience. The exam covers access control systems, operations security, cryptography, applications and systems planning, business continuity and disaster planning, telecommunications and network security, ethics, and the law.

Certified Java Developer (CJD)

An advanced certification from Sun Microsystems designed to evaluate Java programming language skills. See also Certified Java Programmer.

Certified Java Programmer (CJP)

A certification from Sun Microsystems designed to evaluate Java programming language skills. See also Certified Java Developer.

Certified Lotus Professional (CLP)

A certification from Lotus designed to evaluate a wide range of skills and knowledge of Lotus products. Several certifications are available, including CLP: Application Developer, CLP: Principal Application Developer, CLP: System Administrator, CLP: Principal System Administrator, CLP: cc:Mail System Administrator. See also Certified Lotus Specialist.

Certified Lotus Specialist (CLS)

A certification from Lotus designed to evaluate knowledge of a single Lotus product. Options include certification in Lotus Domino, Lotus 1-2-3, Lotus Notes, and cc:Mail. See also Certified Lotus Professional.

Certified Network Professional (CNP)

A certification from the Network Professional Association (NPA) that involves meeting requirements in the areas of client operating systems, networking hardware, network operating systems, communications protocols, and network topologies. Two years of relevant work experience and two vendor-based certifications are required to complete the program.

Certified Novell Administrator (CNA)

A Novell certification program for network administrators responsible for the day-to-day operation of a network. Within the CNA program, a candidate can specialize in one or more Novell products, including IntranetWare, NetWare, or GroupWise. See also Certified Novell Engineer and Master Certified Novell Engineer.

Certified Novell Engineer (CNE)

A Novell certification program for technical professionals concerned with network system design, implementation, and maintenance. Within the CNE program, a candidate can specialize in one or more Novell products, including IntranetWare, NetWare, or GroupWise. See also Certified Novell Administrator and Master Certified Novell Engineer.

Certified Novell Engineer Professional Association (CNEPA)

An association of Certified Novell Engineers (CNAs) that provides benefits, such as workshops demonstrating how to configure and troubleshoot Novell products, as well as admission to network-related events and complementary subscriptions. See also Certified Novell Engineer.

Certified Novell Instructor (CNI)

A Novell certification program for trainers who want to teach Novell courses. Once certified, by passing the appropriate exam at the instructor level, a CNI can teach any instructor-led Novell course, including those for Certified Novell Administrator (CNA), Certified Novell Engineer (CNE), and Master CNE (MCNE). See also Master Certified Novell Instructor.

Certified Performance and Tuning Specialist (CPTS)

A certification from Sybase that tests for proficiency across a wide range of database administration, tuning, and performance concepts. See also Certified Database Administrator.

Certified PowerBuilder Developer Associate (CPDA)

A certification from Sybase designed for experienced PowerBuilder developers that tests knowledge in the areas of client/server architecture, object-oriented programming, relational databases, and Structured Query Language. See also Certified PowerBuilder Developer Professional.

Certified PowerBuilder Developer Professional (CPDP)

A certification from Sybase designed for experienced PowerBuilder developers that requires hands-on experience building PowerBuilder applications as well as a demonstration of good development practices. See also Certified PowerBuilder Developer Associate.

Certified Solutions Expert (CSE)

A pair of Internet certifications from IBM. CSE: Net.Commerce is aimed at the developers of Internet store fronts and other financial transactions over the Internet. CSE: Firewall is a security-related certification.

Certified Unicenter Engineer (CUE)

A certification from Computer Associates designed to evaluate expertise in the Unicenter TNG product line.

CGA

Acronym for “Color Graphics Adapter”; 2 modes and 4 colors – almost obsolete.

CGI

See Common Gateway Interface.

Challenge-Handshake Authentication Protocol (CHAP)

Supported on lines using PPP encapsulation, it is a security feature that identifies the remote end, helping keep out unauthorized users. After CHAP is performed, the router or access server determines whether a given user is permitted access. It is a newer, more secure protocol that PAP. See also Password Authentication Protocol.

Challenge/Response Authentication

A method of authentication used by Microsoft Windows 2000 and other operating systems. When a user contacts a server, the server responds with a challenge, upon which the user then performs a cryptographic operation and returns the result to the server. The server then performs the same operation, and if the two results are the same, the user is considered authentic. See also Clear Text Authentication.

Change Management

The process of managing changes to an environment, such as keeping print drivers up-to-date or installing new software.

Channel

1. In communications, any connecting path that carries information from a sending device to a receiving device. A channel may refer to a physical medium (for example, a coaxial cable) or to a specific frequency within a larger channel.
2. In Internet Relay Chat (IRC), a named forum where you can chat in real time with other users; also known as a chat room.

Channel Interface Processor (CIP)

A channel attachment interface for use in Cisco 7000 series routers that connects a host mainframe to a control unit. This device eliminates the need for an FBP to attach channels.

Channelization

The process of dividing the bandwidth of a communications circuit into smaller increments. See also T1.

Channelized E1

Operating at 2.048Mbps, an access link that is sectioned into 29 B-channels and one D-channel, supporting DDR, Frame Relay, and X.25.

Channelized T1

Operating at 1.544Mbps, an access link that is sectioned into 23 B-channels and one D-channel of 64Kbps each, where individual channels or groups of channels connect to various destinations, supporting DDR, Frame Relay, and X.25. See also T1.

Channel Service Unit (CSU)

A digital mechanism that connects end-user equipment to the local digital telephone loop. Frequently referred to along with the data service unit as CSU/DSU. See also Data Service Unit.

Channel Service Units/Digital Service Units (CSU/DSU)

Network interconnectivity devices that connect a network to the public telephone network. CSUs/DSUs translate signals and shield networks from noise and high voltage on the public network.

CHAP

See Challenge-Handshake Authentication Protocol.

Character

A symbol that corresponds to a key on the keyboard. A character can be a letter, a number, punctuation, or a special symbol and is usually stored as a single byte. A collection of related characters is known as a character set, and the most common character set on PC systems is the American Standard Code for Information Interchange (ASCII). Some larger IBM systems still use Extended Binary Coded Decimal Interchange Code (EBCDIC). In an attempt to rationalize the many international character sets in use these days, some systems use more than one byte to store a character. See also American Standard Code for Information Interchange, Extended Binary Coded Decimal Interchange Code, and Unicode.

Character Set

The set of characters that SQL Server will recognize and therefore store. Of the 256 characters contained in each character set, the first 128 are the same throughout the various code pages. The last 128 characters, also known as extended characters, differ according to the set.

Chat

A real-time, text-based, conversation performed over a computer network or networks. See also Internet Relay Chat.

CHCP

Displays or sets the active code page number.

CHDIR

Displays the name of or changes the current directory.

Check Disk

A Windows utility that checks a hard disk for errors. Check Disk (chkdsk) attempts to fix file-system errors and scans for and attempts to recover bad sectors.

Checkpoint

The mechanism by which SQL Server periodically writes modified data to a hard disk. The DBO of a database may also issue a checkpoint at any time by running the Checkpoint command in the appropriate database. By default, the checkpoint process wakes up once a minute and checks every transaction log for 5 minutes worth of changes to the data pages in cache. If 5 minutes of changes or more are found, the data pages are written to disk. This establishes a known point of consistency between the data pages on hard disk and the transactions stored on hard disk. The 5-minute period is known as the recovery interval and can be modified.

Checkpoint File

The file (EDB.CHK) that contains the point in a transaction log which is the boundary between data that has been committed and data that has not yet been committed to an Exchange database.

Checksum

A test for ensuring the integrity of sent data. It is a number calculated from a series of values taken through a sequence of mathematical functions, typically placed at the end of the data from which it is calculated, and then recalculated at the receiving end for verification.

Child Domain

A relative term that describes a subdomain of another domain.

Chip Creep

A situation in which integrated circuits gradually lose contact with their sockets because of temperature changes.

CHKDSK

Checks a disk and displays a status report.

Choke Packet

When congestion exists, it is a packet sent to inform a transmitter that it should decrease its sending rate.

CIDR

See Classless Interdomain Routing.

CIP

See Channel Interface Processor.

CIPHER

A command-line utility that can be used to encrypt and decrypt files on NTFS volumes.

Cipher Text

Encrypted data. Encryption is the process of translating data into code that is not easily accessible. Once data has been encrypted, a user must have a password or key to decrypt the data. Unencrypted data is known as plain text.

CIR

See Committed Information Rate.

Circuit

A communications channel established between two network devices.

Circuit Filtering

Similar to packet filtering, circuit filtering looks at the session instead of the connection. Circuit filtering allows an administrator to define secondary ports that are opened by an application after the initial connection has been made, thereby allowing the application to function through the firewall.

Circuit Switching

Used with dial-up networks such as PPP and ISDN. Passes data, but needs to set up the connection first – just like making a phone call.

Circular Logging

The process of writing new information in transaction log files over information that has already been committed. Instead of repeatedly creating new transaction logs, the Exchange database engine “circles back” and reuses log files that have been fully committed to the database. Circular logging keeps down the number of transaction logs on the disk. These logs can not be used to recreate a database because the logs do not have a complete set of data. The logs contain only the most recent data not yet committed to a database. Circular logging is the default setting of the Exchange Directory and Information Store databases.

CISA

See Certified Information System Auditor.

CISC

Acronym for “Complex Instruction Set Computing”.

Cisco Discovery Protocol (CDP)

Cisco’s proprietary protocol that is used to tell a neighbor Cisco device about the type of hardware, software version, and active interfaces that the Cisco device is using. It uses a SNAP frame between devices and is not routable.

Cisco FRAD

See Cisco Frame-Relay Access Device.

Cisco Frame-Relay Access Device

A Cisco product that supports Cisco IPS Frame Relay SNA services, connecting SDLC devices to Frame Relay without requiring an existing LAN. May be upgraded to a fully functioning multiprotocol router. Can activate conversion from SDLC to Ethernet and Token Ring, but does not support attached LANs. See also Frame Relay Access Device.

CiscoFusion

Cisco’s name for the internetworking architecture under which its Cisco IOS operates. It is designed to “fuse” together the capabilities of its disparate collection of acquired routers and switches.

Cisco IOS Software

Cisco Internet Operating System software. The kernel of the Cisco line of routers and switches that supplies functionality, scalability, and security for all products under its CiscoFusion architecture. See also CiscoFusion.

CiscoView

GUI-based management software for Cisco networking devices, enabling dynamic status, statistics, and comprehensive configuration information. Displays a physical view of the Cisco device chassis and provides device-monitoring functions and fundamental troubleshooting capabilities. May be integrated with a number of SNMP-based network management platforms.

CISSP

See Certified Information Systems Security Professional.

CJD

See Certified Java Developer.

CJP

See Certified Java Programmer.

Cladding

In fiber-optic cabling, a layer of glass that surrounds the inner core and reflects light back into the core.

Class A Network

Part of the Internet Protocol hierarchical addressing scheme. Class A networks have only 8 bits for defining networks and 24 bits for defining hosts on each network.

Class B Network

Part of the Internet Protocol hierarchical addressing scheme. Class B networks have 16 bits for defining networks and 16 bits for defining hosts on each network.

Class C Network

Part of the Internet Protocol hierarchical addressing scheme. Class C networks have 24 bits for defining networks and only 8 bits for defining hosts on each network.

Class-Definition Object

An object within the AD schema that holds a description of a class of objects.

Classical IP Over ATM

Defined in RFC 1577, the specification for running IP over ATM that maximizes ATM features. Also known as CIA.

Classless Interdomain Routing (CIDR)

A method supported by classless routing protocols, such as OSPF and BGP4, based on the concept of ignoring the IP class of the address, permitting route aggregation and VLSM that enable routers to combine routes in order to minimize the routing information that needs to be conveyed by the primary routers. It allows a group of IP networks to appear to other networks as a unified, larger entity. In CIDR, IP addresses and their subnet masks are written as four dotted octets, followed by a forward slash and the numbering of masking bits (a form of subnet notation shorthand). See also BGP Version 4.

Classless Routing

Routing that sends subnet mask information in the routing updates. Classless routing allows Variable-Length Subnet Mask (VLSM) and supernetting. Routing protocols that support classless routing are RIP version 2, EIGRP, and OSPF.

Clean

A computer, file or disk that is free of viruses (adjective). To remove a virus or other malicious software from a computer, file or disk (verb). See also Disinfection.

Clean Install

A method of Windows 2000 installation that puts the operating system into a new folder and uses its default settings the first time the operating system is loaded.

Cleartext

Unencrypted data. Synonymous with plaintext.

Clear Text Authentication

An authentication method that encodes user name and password information according to a freely available 64-bit encoding utility. See also Challenge-Response Authentication and Encryption.

CLI

See Command-Line Interface.

Click

To quickly press and release the mouse button.

Client

Any device that attaches to the network server. A workstation is the most common type of client. Clients run client software to provide network access. A piece of software which accesses data on a server can also be called a client. See also Server.

Client Access License (CAL)

A special license for each device or user that enables access to Windwos Server 2003 servers. CALs are used with the Per Seat licensing mode.

Client Access Policy

he set of rules defined in ISA that determine which clients are allowed to access particular websites and the protocols they are allowed to use.

Client Address Set

A grouping of internal computers that may be used by an access policy to either allow or deny access for outgoing web requests.

Client License Key Packs

A set of client licenses used by the Terminal Services license server to distribute licenses to your Terminal Services clients.

Client Network Utility

A utility used to configure SQL Server client Net-Libraries. It also reports on the DB-Libraries that are in use for a particular client.

Client Pull

A mechanism used on the Internet whereby a client application, usually a Web browser, initiates a request for services from a Web site. See also Server Push.

Client/Server

A networking model where a specific role of providing services or acting as a client (but not both) is performed by a computer. See also Share and Peer.

Client/Server Applications

Applications that split large applications into two components: computer-intensive processes that run on application servers and user interfaces that run on clients. Client/server applications communicate over the network through interprocess communication mechanisms. See also Client, Server, and Interprocess Communications.

Client Services for NetWare (CSNW)

A service provided with Windows NT that connects a workstation to NetWare file Servers. See also NetWare.

Clipboard

An area of memory, also called a buffer, where text, graphics and commands can be stored to await further action.

Clocking

The mechanism used to count and pace the number of signals being sent and received.

Cloned Applications

A multiple-instance application running in NLB clusters of stateful applications, and that runs against the same, relatively static dataset. An example is a Web server.

CLP

See Certified Lotus Professional and Cell Loss Priority.

CLR

See Cell Loss Ratio.

CLS

1. MS-DOS command that clears the screen.
2. See Certified Lotus Specialist.

Cluster

1. A unit of one or more sectors. It is the minimum amount of space that can be allocated to file on disk.
2. A group of computers acting together as a single logical machine to provide fault tolerance and failover for network services. See also Server Cluster.

Cluster-Aware

A description of an application that can communicate with the Cluster API to receive status and notification information from the cluster.

Cluster Host

An individual computer, or node, that is a member of a server cluster. See also Server Cluster.

Cluster Node

A specific member computer of a cluster.

Cluster Server

A Microsoft software product that enables multiple physical servers to be logically grouped together for reasons of fault-tolerance.

Cluster Service

The Windows service that runs server clusters. Applications and services must be compatible with the Cluster Service in order to respond appropriately to a failure.

Cluster Virus

Cluster viruses modify the directory table entries so the virus starts before any other program. The virus code only exists in one location, but running any program runs the virus as well. Because they modify the directory, cluster viruses may appear to infect every program on a disk. Also known as File System Virus.

CLV

Acronym for “Constant Linear Velocity”.

CMOS

Acronym for “Complementary Metal Oxide Semiconductor”.

CNA

See Certified Novell Administrator.

CNAME Records (Alias)

DNS alias records (also known as canonical name, or CNAME, records) allow you to use more than one name to point to a single host.

CNE

See Certified Novell Engineer.

CNEPA

See Certified Novell Engineer Professional Association.

CNI

See Certified Novell Instructor.

CNP

See Certified Network Professional.

CO

See Central Office.

Coaxial Cable

A type of cabling using a solid metal core surrounded by a plastic sheath.

Code

Synonymous with software but used when the software itself, rather than the utility it provides, is the object of discussion. See also Software.

Code Page

A table in DOS that defines which extended ASCII character set is used in a document.

Cold Boot

The process of starting your PC by turning on the power switch.

Collaboration Data Objects 1.21 (CDO 1.21)

Also known as Active Messaging and OLE Messaging. An application programming interface (API) that allows users and applications to access data objects within an Exchange server. CDO defines the concept of different object classes including messages (IPM.Note), posts (IPM.Post), appointments (IPM.Appointment), and tasks (IPM.Task). Message stores and folder hierarchies can also be manipulated through CDO 1.21. CDO 1.21 is included with Exchange Server 5.5 and its services are supplied from the CDO.DLL file.

Collaboration Data Objects (CDO) for Exchange 2000

An API that is a superset of CDO for Windows 2000. In addition to gaining programmatic access to the Simple Mail Transfer Protocol (SMTP) and Network News Transfer Protocol (NNTP) stacks, CDO for Exchange 2000 provides support for the creation and manipulation of message items, appointments, and contact cards. CDO for Exchange 2000 is included with Exchange 2000 and its services are supplied from the CDOEX.DLL file.

Collaboration Data Objects (CDO) for System Management

Formerly known as Exchange Management Objects (EMO). An API that allows administrators to programmatically access management information on an Exchange 2000 server, including databases and mailboxes. Services are supplied out of the EMO.DLL file.

Collaboration Data Objects (CDO) for Windows 2000

A high-level application programming interface (API) that allows applications to programmatically access Simple Mail Transfer Protocol (SMTP) and Network News Transfer Protocol (NNTP) protocol stacks on a computer running Windows 2000; for example, an automated mailer routine can e-mail Web pages containing reports to employees. CDO for Windows 2000 is included with the Windows 2000 operating system and its services are supplied from the CDOSYS.DLL file.

Collaborative or Cooperative Computing

A form of computing where certain tasks are processed by one computer, and other specific tasks are performed by other computers.

Collapsed Backbone

A nondistributed backbone where all network segments are connected to each other through an internetworking device. A collapsed backbone can be a virtual network segment at work in a device such as a router, hub, or switch.

Collision

A situation that occurs when two or more network devices transmit at the same time, through the same channel. The two signals transmitted meet and cause data to be destroyed. See also Collision Domain.

Collision Domain

The network area in Ethernet over which frames that have collided will spread. Collisions are propagated by hubs and repeaters, but not by LAN switches, routers, or bridges. See also Collision.

Column

The component of a table that holds individual pieces of data. In a database, a row in a table is often referred to as an entity. The column would be an attribute of the entity and describes an aspect of the row. For example, a row of data might describe an individual. A column would describe the name of the individual or the eye color, etc.

COM

Acronym for “Component Object Model”.

COM File

A type of executable file limited to 64kb. These simple files are often used for utility programs and small routines. Because COM files are executable, viruses can infect them. This file type has the extension COM.

Comma-Separated Value Directory Exchange (CSVDE)

A Windows 2000 command line utility for exchanging information between comma-separated-value files and the Active Directory.

Command

An instruction given to a computer to carry out a particular action.

COMMAND

Starts a new instance of the MS-DOS command interpreter.

Command Line

The line on the computer’s screen into which you enter DOS commands.

Command-Line Interface (CLI)

Allows you to configure Cisco routers and switches with maximum flexibility.

Command Prompt

The prompt (C:\>), which appears on the computer’s screen to let you know that MS-DOS is ready to receive a command.

COMMAND.COM

The Operating System’s Command Professor which analyzes what is typed at the keyboard and causes execution of appropriate commands.

Commit

The process whereby completed transactions are put into the database. SQL Server will automatically commit the data at regular intervals, or a manual commit can be initialized by the DBO or SA.

Committed Information Rate (CIR)

Averaged over a minimum span of time and measured in bps, a Frame Relay network’s agreed-upon minimum rate of transferring information.

Common Gateway Interface (CGI)

A standard way that programs can interface with Web servers and allow them to run applications such as search engines and to access databases and other back-end applications. CGI defines the field specifics and control tags to be placed in an HTML document, the environment variables where the Web server places information for use by scripts, and the flow of information between client Web browser, the server, and the Web server scripts. CGI is platform-independent. See also Hypertext Markup Language, Script, and Web Server.

Common Part Convergence Sublayer (CPCS)

One of two AAL sublayers that is service-dependent, it is further segmented into the CS and SAR sublayers. The CPCS prepares data for transmission across the ATM network; it creates the 48-byte payload cells that are sent to the ATM layer. See also ATM Adaptation Layer and ATM Layer.

Communication Flow

A description of the sharing of information and the free flow of ideas within a company. As such, it is both a physical aspect (who talks to whom) and a philosophical aspect (how much freedom of information exists) of AD design.

Communication Protocol

For computers engaged in telecommunications, the protocol (i.e., the settings and standards) must be the same for both devices when receiving and transmitting information. A communications program can be used to ensure that the baud rate, duplex, parity, data bits, and stop bits are correctly set.

COMP

Compares the contents of two files or sets of files.

Compact Disk File System (CDFS)

A file system used by Windows 2000 to read the file system on a CD-ROM.

Compact Disk-Read Only Memory (CD-ROM)

A media for storing extremely large software packages on optical read-only discs. CD-ROM is an adaptation of the CD medium used for distributing digitized music. CD-ROM discs can hold up to 650MB of information and cost very little to produce in quantity. See also Hard Disk Drive.

Companion Virus

Companion viruses use a feature of DOS that allows software programs with the same name, but with different extensions, to operate with different priorities. Most companion viruses create a COM file which has a higher priority than an EXE file with the same name. Thus, a virus may see a system contains the file PROGRAM.EXE and create a file called PROGRAM.COM. When the computer executes PROGRAM from the command line, the virus (PROGRAM.COM) runs before the actual PROGRAM.EXE. Often the virus will execute the original program afterwards so the system appears normal.

Compatibility Script

A script that helps applications run on a Terminal Services server. Compatibility scripts should be run after the program is installed to achieve the best performance on a Terminal Services server. See also Terminal Services Server.

Components

Interchangeable elements of a complex software or hardware system. See also Module.

Component Object Model (COM)

COM is an object-oriented architecture for building reusable application components. COM provides a specification, or model, for what an object is and it provides services for both the creation of objects and the communication between a client and the server objects. COM replaces OLE (Object Linking and Embedding) and has other advantages. COM’s most notable advances are its binary compatibility and cross-platform development capabilities, code reusability, and version control.

COM Port

Communications port. A serial hardware interface conforming to the RS-232 standard for low-speed serial communications. See also Modem and Serial.

Composite Metric

Used with routing protocols, such as IGRP and EIGRP, that use more than one metric to find the best path to a remote network. IGRP and EIGRP both use bandwidth and delay of the line by default. However, Maximum Transmission Unit (MTU), load, and reliability of a link can be used as well.

Compression

A space optimization scheme that reduces the size (length) of a data set by exploiting the fact that most useful data contains a great deal of redundancy. Compression reduces redundancy by creating symbols smaller than the data they represent and an index that defines the value of the symbols for each compressed set of data.

Compromise

To access or disclose information without authorization.

CompTIA

Acronym for “Computer Technology Industry Association”. (http://www.comptia.org)

Computer

A device capable of performing automatic calculations based upon lists of instructions called programs. The computer feeds the results of these calculations (output) to peripheral devices that can represent them in useful ways, such as graphics on a screen or ink on paper. See also Microprocessor.

Computer Management

A consolidated tool for performing common Windows 2000 management tasks. The interface is organized into three main areas of management: System Tools, Storage, and Services and Applications.

Computer Name

A 1- to 15-character NetBIOS name used to uniquely identify a computer on the network. See also Network Basic Input/Output System.

Computer Object

An Active Directory object that is a security principal and that identifies a computer that is part of a domain.

Concentrator

This is a term for a hub or MSAU. A connectivity device used to connect multiple twisted-pair cables together. See also Hub.

Concurrency

The ability of SQL Server to support multiple users at the same time, even if those users want the same data.

Conditional Forwarder

A type of DNS server that will forward DNS queries for external DNS names to DNS servers outside of its own network based on the domain name in the query. Use when DNS clients in separate networks resolve each others’ names without having to query a DNS server on the Internet.

Conference Technology Provider (CTP)

A provider of data conferencing services such as real-time video, audio, and telephony integration.

Conferencing Management Service (CMS)

The network service that coordinates the booking of virtual resources for online meetings in the Exchange Conference Service. Each site (not domain) normally has an active Conferencing Management Service to allow fast connection for data conferencing users.

Confidentiality

Ensures that data is secret to all except the authorized parties to a data transaction.

CONFIG.SYS

A special file that allows the system to be configured closer to requirements.

Configuration Connection Agreement (ConfigCA)

A special Connection Agreement implemented as part of the Active Directory Connector that replicates configuration naming context data from downlevel Exchange 5.x sites to administration groups in Active Directory and vice versa. ConfigCAs work in conjunction with the Site Replication Service.

Configuration Register

A 16-bit configuration value stored in hardware or software that determines how Cisco routers function during initialization. In hardware, the bit position is set using a jumper. In software, it is set by specifying specific bit patterns used to set startup options, configured using a hexadecimal value with configuration commands.

Congestion

A condition in which a network transmission medium is overwhelmed with network traffic, causing network performance to decline.

Congestion Avoidance

To minimize delays, the method an ATM network uses to control traffic entering the system. Lower-priority traffic is discarded at the edge of the network when indicators signal it cannot be delivered, thus using resources efficiently.

Congestion Collapse

The situation that results from the retransmission of packets in ATM networks where little or no traffic successfully arrives at destination points. It usually happens in networks made of switches with ineffective or inadequate buffering capabilities combined with poor packet discard or ABR congestion feedback mechanisms.

Connection Admission Control (CAC)

The sequence of actions executed by every ATM switch while connection setup is performed in order to determine if a request for connection is violating the guarantees of QoS for established connections. Also, CAC is used to route a connection request through an ATM network.

Connection Agreement

The configuration of information to be replicated using the Active Directory Connector (ADC). This configuration information includes the servers that participate in the replication, which object classes (mailbox, custom recipient, distribution list user, contact, and group) to replicate, containers and organizational units to use for object placement, and the activity time schedule.

Connection ID

Identifications given to each Telnet session into a router. The show sessions command will give you the connections a local router will have to a remote router. The show users command will show the connection IDs of users telnetted into your local router.

Connectionless

Connectionless mode does not provide elaborate internal control mechanisms; instead, connectionless mode relegates all error-correcting and retransmitting processes to the source and destination nodes. The end nodes acknowledge the receipt of packets and retransmit if necessary, but internal nodes do not participate in flow control and error correction (other than simply forwarding messages between the end nodes).

Connectionless Service

A type of connection service that does not establish a connection (path) before transmission. This type of communication is fast, but is not very reliable.

Connection Oriented

In connection-oriented mode, the chain of links between the source and destination nodes forms a kind of logical pathway connection. The nodes forwarding the data packet can track which packet is part of which connection. This enables the internal nodes to provide flow control as the data moves along the path.

Connection-Oriented Service

A type of connection service in which a connection (a path) is established and acknowledgements are sent. This type of communication is reliable but has a high overhead.

Connection-Specific DNS Suffix

The DNS suffix is added to resolver requests on a particular connection. Allows the proper lookup of an unqualified name.

Connection Type

A component of an IPSec policy that specifies whether the rule applies to LAN connections, dial-up connections, or both.

Connectors

Software that manages the transport of data between Exchange sites (e.g., the Site Connector) or between Exchange and a foreign message system (e.g., the X.400 Connector, Microsoft Mail Connector, and the Internet Mail Service). See also Gateways.

Connector Cost

A numeric value assigned to a connector. The Message Transfer Agent (MTA) uses connector cost as a criterion when it chooses between multiple connectors that support the same address space.

Connector Type

The connection between the network adapter card and the transmission media.

Console Port

Typically an RJ-45 port on a Cisco router and switch that allows Command-Line Interface capability.

Constant Bit Rate

Abbreviated CBR. A type of Asynchronous Transfer Mode (ATM) service reserved for voice or video or other data that must be transmitted at a constant rate and are intolerant of data loss. See also Asynchronous Transfer Mode, Available Bit Rate, Unspecified Bit Rate and Variable Bit Rate.

Consultative Committee on International Telegraphy and Telephony (CCITT)

A committee, sponsored by the United Nations, that defines network standards, including X.400 and X.500. This committee has been recently renamed to International Telecommunications Union/Telecommunications Standardization Sector (ITU/TSS). See also International Telecommunication Union.

Contact

A non-security principal that represents a user outside of the organization. A contact will generally have an e-mail address, facilitating messaging between the local organization and the remote object. A contact is similar to a custom recipient in Exchange Server 5.5.

Contact Object

Active Directory objects that store contact information.

Container

An Active Directory object that holds other Active Directory objects. Domains and organizational units are examples of container objects. See also Active Directory, Domain, and Organizational Unit.

Container Object

An object in the Exchange hierarchy that contains and groups together other objects. The organization object is a container object that contains the Folders, Global Address List, and Site objects.

Contention

Computers contend for use of the transmission medium. Any computer in the network can transmit at any time (first come, first serve).

Context Level

Refers to a level in the Exchange hierarchy that does not inherit permissions from other portions of the hierarchy. The three context levels are organization, site, and configuration. Administrative permissions must be assigned to users or groups individually at each of the three levels.

Control Direct VCC

One of three control connections defined by Phase I LAN Emulation; a bi-directional virtual control connection (VCC) established in ATM by an LEC to an LES. See also Control Distribute VCC.

Control Distribute VCC

One of the three control connections defined by Phase I LAN Emulation; a unidirectional virtual control connection (VCC) set up in ATM from an LES to an LEC. Usually, the VCC is a point-to-multipoint connection. See also Control Direct VCC.

Control Panel

A software utility that controls the function of specific operating system services by allowing users to change default settings for the service to match their preferences. The Registry contains the Control Panel settings on a system and/or per-user basis. See also Registry and Accounts.

Conventional Memory

The first 640 KB of base memory, used by DOS programs.

Convergence

The process required for all routers in an internetwork to update their routing tables and create a consistent view of the network, using the best possible paths. No user data is passed during a convergence time.

Convergence Sublayer

Abbreviated CS. One of two sublayers that make up the ATM Adaptation Layer; the other being the segmentation and reassembly sublayer (SAR). The convergence sublayer is the upper layer that provides the interface for the various ATM services, pads the cells, and adds headers and trailers before passing the cell to the SAR. See also ATM Adapation Layer and Segmentation and Reassembly Sublayer.

Convergence Time

The time it takes a change from any RIP router to propagate to all other routers in the internetwork.

CONVERT

A command-line utility used to convert a partition from FAT16 or FAT32 to the NTFS file system.

Cookie

Cookies are blocks of text placed in a file on your computer’s hard disk. Web sites use cookies to identify users who revisit the site. Cookies might contain login or registration information, “shopping cart” information or user preferences. When a server receives a browser request that includes a cookie, the server can use the information stored in the cookie to customize the Web site for the user. Cookies can be used to gather more information about a user than would be possible without them.

Cooperative Multitasking

A multitasking scheme in which each process must voluntarily return time to a central scheduling routine. If any single process fails to return to the central scheduler, the computer will lock up. Both Windows and the Macintosh operating system use this scheme. See also Preemptive Multitasking and Windows 3.11 for Workgroups.

Coprocessor

A processor for doing specialized tasks, such as a math coprocessor. It reduces the load on the CPU.

Copy

This is the other Microsoft NT NTBACKUP utility-specific command. This command backs up all selected files, but does not modify the archive bit of those files being backed up. This is a useful option if you wish to do a backup outside the regular backup schedule and do not wish to alter the normal backup routine.

COPY

Copies one or more files to another location.

Copy Backup

A backup type that backs up selected folders and files but does not set the archive bit (indicating that the file has been backed up).

Copy Left

The copyright or General Public License of the Free Software Foundation (FSF), which states that any of the software developed using free software from FSF must be distributed to others without charge. See also Open Source Software.

Core Layer

Top layer in the Cisco three-layer hierarchical model, which helps you design, build, and maintain Cisco hierarchical networks. The core layer passes packets quickly to distribution-layer devices only. No packet filtering should take place at this layer.

Corporate Office

A location in which the company has invested heavily in facilities, information services staff, and hardware or is heavily staffed.

Cost

Also known as path cost, an arbitrary value, based on hop count, bandwidth, or other calculation, that is typically assigned by a network administrator and used by the routing protocol to compare different routes through an internetwork. Routing protocols use cost values to select the best path to a certain destination: the lowest cost identifies the best path. Also known as path cost. See also Routing Metric.

Cost Center Model

Usually a hybrid of all of the other business models. In this model, the functions of business are once again divided into groups – based on projects, products/services, or traditional departments – just as they are in the other models. The big difference is in how those groups interact. Each group is seen as a separate business entity within the company. Groups charge each other for the services they provide.

Counter

A performance-measuring tool used to track specific information regarding a system resource, called a performance object. All Windows 2000 system resources are tracked as performance objects, such as Cache, Memory, Paging File, Process, and Processor. Each performance object has an associated set of counters. Counters are set through the System Monitor utility.

Count to Infinity

A problem occurring in routing algorithms that are slow to converge where routers keep increasing the hop count to particular networks. To avoid this problem, various solutions have been implemented into each of the different routing protocols. Some of those solutions include defining a maximum hop count (defining infinity), route poisoning, poison reverse, and split horizon.

CPCS

See Common Part Convergence Sublayer.

CPDA

See Certified PowerBuilder Developer Associate.

CPDP

See Certified PowerBuilder Developer Professional.

CPE

See Customer Premises Equipment.

CPI

Acronym for “Common Programming Interface”.

CP/M

Acronym for “Control Program for Microcomputer”.

CPS

Acronym for “Characters per Second”.

CPTS

See Certified Performance and Tuning Specialist.

CPU

See Central Processing Unit and Microprocessor.

Crankback

In ATM, a correction technique used when a node somewhere on a chosen path cannot accept a connection setup request, blocking the request. The path is rolled back to an intermediate node, which then uses GCAC to attempt to find an alternate path to the final destination.

CRC

See Cyclic Redundancy Checksum.

Creator Group

The Windows 2000 or Windows Server 2003 special group that created or took ownership of the object (rather than an individual user). When a regular user creates an object or takes ownership of an object, the username becomes the Creator Owner. When a member of the Administrators group creates or takes ownership of an object, the Administrators group becomes the Creator Group.

Creator Owner Group

The Windows 2000 special group that includes the account that created or took ownership of an object. The account, usually a user account, has the right to modify the object, but cannot modify any other objects that were not created by the user account.

CRL

See Certificate Revocation List.

CRL Distribution Point

List of locations where CRLs are published for client or server access.

Cross-Forest Trusts

A new Windows Server 2003 feature that lets you implement trusts between all domains in one forest and all domains in another forest.

Crosstalk

Interference, or noise, created on a network transmission medium by another physically adjacent medium. This interference can corrupt data.

CRT

Acronym for “Cathode Ray Tube”.

Cryptography

The process of securing and maintaining the secrecy of data communications through encryption/decryption systems.

Cryptology

The study and implementation of hiding and revealing information.

CSE

See Certified Solutions Expert.

CSMA/CA

Acronym for “Carrier-Sense Multiple Access with Collision Avoidance”.

CSMA/CD

See Carrier Sense Multiple Access Collision Detect.

CSNET (Computer+Science Network)

A large computer network, mostly in the U.S. but with international connections. CSNET sites include universities, research labs, and some commercial companies. Now merged with BITNET to form CREN.

CSNW

See Client Services for NetWare.

CSU

See Channel Service Unit.

CTD

See Cell Transfer Delay.

CTL

See Certificate Trust List.

CTS

Acronym for “Clear to Send”.

CTTY

Changes the terminal device used to control your system.

CUA

Acronym for “Common User Access”.

CUE

See Certified Unicenter Engineer.

Current Directory

The directory that is searched first for a requested file.

Current State

A mechanism that uses the clock count to analyze the current state of the signal during that count. Thus the signal is either “on” or “off” during the clock count.

Cursor

The blinking line indicating where the next input can be entered.

Customer Premises Equipment (CPE)

Items such as telephones, modems, and terminals installed at customer locations and connected to the telephone company network.

Custom Recipient

An Exchange recipient object that represents a foreign message recipient. Custom recipients allow Exchange clients to address messages to foreign mail users.

Cut-Through Frame Switching

A frame-switching technique that flows data through a switch so that the leading edge exits the switch at the output port before the packet finishes entering the input port. Frames will be read, processed, and forwarded by devices that use cut-through switching as soon as the destination address of the frame is confirmed and the outgoing port is identified.

Cyclic Redundancy Checksum (CRC)

A redundancy check in which the check key is generated by a cyclic algorithm. Also, a system checking or error checking performed at both the sending and receiving station after a block check character has been accumulated.