C

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.

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.

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.

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 DSUs (i.e., CSU/DSU).

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.

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.

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.

Collision
A collision occurs when two or more nodes transmit data simultaneously on the same physical media. This can occur in Ethernet LANs using a bus topology where all nodes share the same physical media.

Collision Domain
Collision domain is the portion of a network where all nodes receive every frame transmitted; it is the part of a network in which nodes compete for access to the same physical medium.

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.

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.