- cable modem
A device that provides Internet access over cable television lines.
- cable tester
A device that is used to check for electrical continuity along a length of cable. Cable tester is a generic term that can be applied to devices such as volt/ohm meters and TDRs.
- caching-only server
A type of DNS server that operates the same way as secondary servers except that a zone transfer does not take place when the caching-only server is started.
- carrier
A signal that carries data. The carrier signal is modulated to create peaks and troughs, which represent binary bits.
- CDDI (Copper Distributed Data Interface)
An implementation of the FDDI standard that uses copper cable rather than optical cable.
- Centronics connector
A connector that uses clips that snap into place to secure the connector. Used with external SCSI devices and some printer connections.
- change control
A process in which a detailed record of every change made to the network is documented.
- channel
A communications path used for data transmission.
- checksum
A basic method of error checking that involves calculating the sum of bytes in a section of data and then embedding the result in the packet. When the packet reaches the destination, the calculation is performed again to make sure that the value is still the same.
- CIDR (classless interdomain routing)
An IP addressing scheme that allows a single IP address to designate many unique IP addresses. CIDR addressing uses an IP address followed by a '/' and the IP network prefix. An example CIDR address would be 192.168.100.0/16. CIDR is sometimes referred to as Supernetting.
- circuit switching
A method of sending data between two parties in which a dedicated circuit is created at the beginning of the conversation and broken at the end. All data transported during the session travels over the same path, or circuit.
- Class A network
A TCP/IP network that uses addresses from 1 to 126 and supports up to 126 subnets with 16,777,214 unique hosts each.
- Class B network
A TCP/IP network that uses addresses from 128 to 191 and supports up to 16,384 subnets with 65,534 unique hosts each.
- Class C network
A TCP/IP network that uses addresses from 192 to 223 and supports up to 2,097,152 subnets with 254 unique hosts each.
- client
A node that uses the services from another node on a network.
- client/server networking
A networking architecture in which front-end, or client, nodes request and process data stored by the back-end, or server, node.
- clustering
A technology that allows two or more computers to act as a single system to provide improved fault tolerance, load balancing and failover capability.
- coaxial cable
A data cable, commonly referred to as coax, that is made of a solid copper core that is insulated and surrounded by braided metal and covered with a thick plastic or rubber covering. Coax is the standard cable used in cable television and in older bus topology networks.
- config
A command that is used on a NetWare server to see basic information such as the server name, NDS information, and the details of network interface configurations.
- collision
The result of two frames transmitting simultaneously on an Ethernet network and colliding, thereby damaging both frames.
- collision domain
A segment of an Ethernet network that is between managing nodes, where only one packet can be transmitted at any given time. Switches, bridges, and routers can be used to segment a network into separate collision domains.
- collision light
An LED on networking equipment that flashes to indicate a collision on the network. A collision light can be used to determine whether the network is experiencing a large number of collisions.
- COM port (communication port)
A connection through which serial devices and a computer's motherboard can communicate. A COM port requires standard configuration information, such as an IRQ, an I/O address, and a COM port number.
- communication
The transfer of information between nodes on a network.
- concentrator
A device that combines several communications channels into one. It is often used to tie multiple terminals together into one line.
- connectionless communication
Packet transfer in which delivery is not guaranteed.
- connection-oriented communication
Packet transfer in which delivery is guaranteed.
- connectivity
The linking of nodes on a network in order for communication to take place.
- copy backup
Normally, a backup of the entire hard drive. A copy backup is similar to a full backup, except that the copy backup does not alter the state of the archive bits on files.
- cost
A value that is used to encourage or discourage the use of a certain route through a network. Routes that are to be discouraged are assigned a higher cost, and those that are to be encouraged are assigned a lower cost. - See also [metric]
- cracker
A person who attempts to break software code or gain access to a system to which he or she is not authorized. - See also [hacker]
- cracking
The process of attempting to break software code, normally to defeat copyright protection or alter the software's functioning. Also the process of attempting to gain unauthorized access to a computer system. - See also [hacking]
- CRC (cyclical redundancy check)
A method used to check for errors in packets that have been transferred across a network. A computation bit is added to the packet and recalculated at the destination to determine whether the entire content of the packet has been transferred correctly.
- crimper
A tool that is used to join connectors to the ends of network cables.
- crossover cable
A UTP cable in which the 1 and 3 wires and the 2 and 6 wires are crossed for the purposes of placing the transmit line of one device on the receive line of the other. Crossover cables can be used to directly connect two like devicesfor example, two computer systemsor as a means to expand networks that use devices such as hubs or switches.
- crosstalk
Electronic interference that is caused when two wires are too close to each other.
- CSMA/CA (carrier-sense multiple-access with collision avoidance)
A contention media access method that uses collision-avoidance techniques.
- CSMA/CD (carrier-sense multiple-access with collision detection)
A contention media access method that uses collision-detection and retransmission techniques.
- cut-through packet switching
A switching method that does not copy the entire packet into the switch buffers. Instead, the destination address is captured into the switch, the route to the destination node is determined, and the packet is quickly sent out the corresponding port. Cut-through packet switching maintains a low latency.
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