C

Cable Categories
There are several cable categories used to describe the different types of twisted pair networks as follows:

• Categories 1 and 2 are used for low-speed data transmission and voice.
• Category 3 is the most common type of network cabling in use today. It is used for 4 and 16 megabits per second (Mbps) Token Ring and 10Base T networks.
• Category 4 is used for voice and data transmission rates of 20 Mbps.
• Category 5 is used for voice and data transmission rates up to 100 Mbps. It is the most popular type of network cabling being used in new installations.

Capacity
Capacity is the data rate capability of a data communication component to carry out its intended function. It is typically used to describe the capability of a communication channel or link. For example, the capacity of a T1 channel is 64 kilobits per second (Kbps).

Carrier Sense Multiple Access with Collision Detections (CSMA/CD)
The inventors of Ethernet chose the CSMA/CD technique for controlling access to the medium.

Cascading Style Sheets (CSS)
Cascading style sheets are a specification, developed by W3C, that allow the visual appearance of a Web page or site to be defined in a separate style sheet file.

Cell
A cell is a unit of information similar to a frame. A cell, however, is very small (53 bytes) and fixed in length. Cells are typically associated with asynchronous transfer mode (ATM) technology.

Central Processing Unit (CPU)
A CPU is the processor in a computer that processes the code and associated data in a computer system.

Certificate Authority (CA)
A CA is an organization that creates digital certificates for individuals and Web servers, after verifying the identity of those persons or sites. A CA signs each digital certificate with its own digital signature, thus vouching for the identity and trustworthiness of the owners of the certificates.

Channel
Generically speaking, a channel is a communications path between two or more communicating devices. Channels are also referred to as links, lines, circuits, and paths. In the mainframe environment, the channel is the path between the host computer and a controller device.

Character Transparency
Character transparency is a feature of a transmission protocol that allows certain control characters to pass unchanged across a communications link.

Chatty Host
A network node that sends out frequent advertisements about its services, such as a printer or networking server, is referred to as a chatty host. For example, RIP is considered a chatty protocol.

Checksum
Checksum is the number of bits in a transmitted unit of data. A checksum is appended to a data unit as a simple error-detection method. The receiving node counts the data bits and compares the result to the checksum, to see whether all bits have arrived. If the numbers match, the transmission was likely complete. TCP and UDP provide checksum count and verification.

Circuit-Switched Networks
Circuit-switched networks establish a physical connection between two nodes. A packet is passed between nodes by "switching" it through intermediate points, either through other nodes or a host computer.

Cladding
Cladding is one of two pieces that make up a fiber optic cable; the other piece is a glass core. A plastic coating covers the fiber. The glass cladding has a lower refractive index than the core, and reflects the light signal as it propagates down the fiber.

Class
Class is an object-oriented term not used in ASP. A class describes to the computer the inner workings of an object. It is similar to an object's blueprint.

Classical IP Over ATM (CIP)
CIP is an approach that allows legacy IP systems to use ATM as the transport technology.

Client
The client portion of a client/server architecture is any node or workstation used by a single user. If multiple users also share the same workstation, it becomes a server. Examples of clients are Microsoft Windows NT Workstation and Windows 95.

Client/Server
Client server or client/server is a mode in computer networking in which individual computers can access data or services from a common high-performance computer. For instance, when a PC needs data from a common database located on a computer attached to a LAN, the PC is the client and the network computer is the server.

Client-Side Script
A client-side script is a program that runs on the client side of a client/server process. For example, client-side scripts in Web pages run on Web clients (browsers).

Clustering
Clustering is a grouping of devices or other components, typically used for performance enhancement. Clustering computers to execute a single application speeds up the operation of the application.

Coder/Decoder (Codec)
A codec is a hardware/software device that takes an analog video signal and converts (codes) it to digital format for compression and transmission. On the receiving end, the digital signal is put back (decoded) into the original analog signal.

Collapsed Backbone
A network topology that uses a multiport device, such as a switch or router, to carry traffic between network segments or subnets is a collapsed backbone. This is in contrast to a standard backbone which, in the case of Ethernet, consists of a single common bus cable to which nodes and subnets are connected.

Collection
A collection is a construct within an ASP script that holds a number of objects. The number of objects in a collection might be as few as zero. There are no upper limits. In most circumstances a collection might hold objects of only one type. For example, an object representing a set of database results might contain a Fields collection that contains numerous Field objects.

Collision
A collision occurs in an Ethernet network when two frames are put onto the physical medium at the same time. When a collision occurs, the data on the physical segment is no longer valid.

Collision Domain
Collision domain is the portion of a network where all nodes receive every frame transmitted.

Colocation
Colocation refers to a business agreement, and a physical space, in which communication companies transfer calls and services to each other. For example, long distance carriers often colocate with local telephone companies. In a physical colocation, each company owns and maintains its own equipment. In a virtual colocation, one company leases the use of equipment owned and maintained by another.

Common Gateway Interface (CGI)
CGI is a standard specification for creating Web server programs that accept data from Web clients, process the data, and return a result. For example, each HTML form needs a corresponding CGI program to process form data sent to its Web site. CGI programs can be written in a variety of languages, including C, Perl, Visual Basic, and Java.

Common Management Information Protocol (CMIP)
CMIP is an ITU-TSS standard for network management message formats and procedures.

Compiler
A compiler is a software program that takes code from a programming language like C or C++ and converts it into machine-readable, executable code to be run on a Web client, Web server, or any other computer for that matter. Both compilers and interpreters are used to execute programs on Web clients and servers.

Compression
Compression refers to the process of reducing the number of bits required to represent data without altering the meaning of the information being conveyed by the data. The primary reason for using compression techniques is to optimize the use of the communication channel.

Conceptual Design
Conceptual Design is another common name given to the Logical Design phase.

Connection-Oriented
The term connection-oriented refers to a protocol mode used in data communication networks where the sending and receiving computers in a network remain connected for the duration of the session. The computers stay in contact while the packets or frames are being sent back and forth.

Connectionless
A term used to describe data transfer that requires the establishment of a virtual connection.

Convergence
The process of updating and synchronizing all routing tables in a network, so that all routers agree on new metrics or topology is referred to as convergence. Large networks converge more slowly than small networks, because of the larger number of routers that must be updated after each change.

Copper Distributed Data Interface (CDDI)
CDDI is a version of FDDI that runs on copper wiring such as twisted pair.

Channel Service Unit (CSU)
A CSU is a device, such as a T1 circuit, that connects customer equipment to digital transmission facilities. The CSU is the device that actually generates the transmission signals on the local loop (that is, the telephone channel). CSUs are normally coupled with data service units (DSUs) (i.e., CSU/DSU).

Criminal Hacker (Cracker)
A cracker is someone who breaches a secure system for fun or profit, and possibly steals information or damages data.

Cyclic Redundancy Check (CRC)
CRC is the mathematical process used to check the accuracy of the data being transmitted across a network. Before transmitting a block of data, the sending station performs a calculation on the data block and appends the resulting value to the end of the block. The receiving station takes the data and the CRC value, and performs the same calculation to check the accuracy of the data.