Glossary Co-Cz0-A | B | C-Cn | Co-Cz | D | E | F-G | H-I | J-L | M | N-O | P-Q | R | S | T | U-Z
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- Coating: A material put on a
fiber during the drawing process to protect it from the
- Coaxial Cable: A type of electrical cable in which a
signal central wire that carries the signal is surrounded by insulation & then
a complete metal shield. Ethernet, thinnet & RG62 cables are
- Coaxial Connector: A connector that has coaxial
construction & is used with coaxial cable.
- Code: A set of unambiguous
rules specifying the way in which data may be represented.
Effect: The inductive effect exhibited by a spiral-wrapped shield,
especially above audio frequencies.
- Collapsed Backbone: A local area
network configuration wherein bridging & routing functions are located at the
main cross-connect & accessed via optical fiber (usually 2 or 4). Concentrators
(twisted pair to fiber) remain at the horizontal
- Collision: The result of simultaneous transmission by
two DTEs on a shared bus. Both DTEs must re-transmit the data (one at a time or
- Collision Detect: A signal that one or more stations
are contending with the local station's transmission. The signal is sent by the
physical layer to the data link layer on an Ethernet/IEEE 802.3
- Collision Domain: See Segment
- Color Code: A color
system for wire or circuit identification by use of solid colors, traces,
braids, surface printing, etc.
- Comite Consultatif
International de Telegraphique et Telephonique: (CCITT) French for
"International Telephone & Telegraph Advisory Council." It's an organization
that plays a major role in the United National International Telecommunications
Union (ITU). The CCITT is responsible for making technical recommendations
about communications systems worldwide. Every four years, CCITT updates the
- Common Carrier: Public transmission link such as the Bell
or General Telephone systems
- Common Management
Information Protocol: (CMIP) the network management protocol defined by the
OSI specifications. CMIP is used to convey CMIS defined operations over an OSI
- Common Management Information Services:
(CMIS) The portion of the OSI network management specification which defines
the management services available to a network management system. CMIS works
- Communications Control Unit: (CCU) A
computer attached to a host & dedicated to performing data communications
functions. Its purpose is to enable the host to perform other tasks. A CCU is
also called a "Front End Processor"
- Communications Server: An
intelligent device (a computer) providing communications functions; an
intelligent, specially configured node on a local area network, designed to
enable remote communications access & exit for LAN users.
- Community Antenna Television: (CATV) Cable Television; data
communications based on radio frequency (RF) transmission, generally using 75
ohm coaxial cable as the transmission medium; communications via coaxial cable
where multiple frequency divided channels allow mixed transmissions to be
carried simultaneously; broadband.
- Compaction: See Compression
- Composite Cable: Cable containing more
than one gauge size or a variety of circuit types, e.g. pairs, triples, quads,
- Composite Link: The line or circuit connecting a pair
of multiplexers or concentrators; the circuit carrying multiplexed
- Compression: Any of several techniques that
reduce the number of bits required to represent information in data
transmission or stage (thus conserving bandwidth and/or memory), in which the
original form of the information can be reconstructed; also called
- Computer Emergency Response Team:
(CERT) The CERT was formed by DARPA in November 1988 in response to the
Internet worm incident. CERT exists to facilitate Internet-wide response to
computer security events involving Internet hosts & to conduct research
targeted at improving the security of existing systems. They maintain an
archive of security-related issues on their FTP server
A communications device that allows a shared transmission medium to accommodate
more data sources than channels currently available within the transmission
- Concentric Stranding: A group of uninsulated wires twisted
together & containing a center core with subsequent layers spirally wrapped
around the core to form a single conductor.
- Conditioning: The
addition of equipment to improve ("tune") the transmission characteristics of a
dedicated voice grade telephone line. Conditioning is done to allow for an
increase in transmission speed (Bit rate) without increasing the error
- Conductivity: Any material that allows electrons to flow
measured by the voltage applied.
- Conductor: A material that offers
little resistance to the flow of electrical current.
- Conduit: A
raceway of circular cross-section of the type permitted under the appropriate
- Configuration Management: A network management
function defined by the International Standards Organization (ISO). It involves
installing, reinitializing & modifying hardware & software.
Hardware: A device providing mechanical cable
- Connection: A term used in the networking environment
to describe the path between two devices. A connection allows the exchange of
information between two or more devices. Equivalent terms are session &
- Connection-Oriented: Refers to a protocol which uses virtual
circuits; the nodes which are the endpoint of the connection, or circuit,
maintain state control information. This allows them to correlate each packet
with previously received packets to provide error-free, loss-less packet
- Connectionless Service: A protocol or service which does
not require that a virtual circuit be established between the endpoints: each
packet is processed independently. All commonly used LAN's provide
connectionless service as the basic packet delivery service
- Console: The terminal used to configure network devices at
boot or start up time.
- Contention: A situation when multiple users
compete for a transmission channel within a multiplexed digital
- Continuity Check: A test performed on a length of finished
wire or cable to determine if the electrical current flows continuously
throughout the length. Each conductor may also be checked against each other to
ascertain that no shorts exist.
- Control Cable: A cable used for
remote control operation of any type of electrical power
- Control Signals: A category of signals in a DTE to DCE
interface specification. These signals control the data transmission.
- Coordinating Committee for Intercontinental Research
Networks: (CCIRN) A committee that provides a forum for North American &
European network research organizations to cooperate & plan.
Typically made out of glass, the core is the light conducting central portion
of the optical fiber. It has a higher refractive index than the
- Coupling: The transfer of energy between two or more cables
or components of a circuit.
- Coupling Loss (fiber optic): Signal
losses due to small differences in numerical aperture, core diameter, core
concentricity & tolerances in splicing connectors when two fibers are aligned.
Also known as splicing loss & transfer loss.
- Coverage: The calculated
percentage which defines the completeness with which a metal braid covers the
underlying surface. The higher percentage of coverage, the greater the
protection against external interference.
- CPU: See Central Processing Unit
- CRC: See Cyclic Redundancy Check
- Cross-connect: A facility for
the interconnection & termination of cabling.
- Crossover: Conductor
which runs through the cable & connect to a different pin number at each
- Crosstalk: The unwanted electrical currents in conductors caused
by electromagnetic or electrostatic coupling from other conductors, or, the
signal on 1 pair leaks or jumps onto & adjacent pair. It is measured in
decibels (dB). Crosstalk must be at least 10 dB greater than the total cable
- CRT: See Cathode Ray
- CSA: See Canadian Standards
- CSMA: See Carrier Sense
- CSMA/CD: See Carrier
Sense Multiple Access/Collision Detection
- CSU: See Channel Service Unit
- Current Loop: Method of interconnecting terminals &
transmitting signals a mark (binary1) is represented by current on the line, &
a space(binary 0) is represented by the absence of
- Cut-through: Technique for examining incoming packets
whereby an Ethernet switch looks only at the first few bytes of a packet before
forwarding or filtering it. This process is faster than looking at a whole
packet, but also allows some bad packets to be forwarded.
- Cyberspace: The "world of computers & the society that
gathers around them," as referred to by William F. Gibson in his fantasy novel
"Neuromancer." It now loosely refers to the online world & even more loosely to
- Cyclic Redundancy Check: (CRC) An
error-detecting code appended to a packet to help the receiver determine if
errors were introducing during transmission. The CRC is specialized checksum
computed over the entire packet & added to the packet by transmitters LAN
controller hardware, & is checked for correctness by the receiving station's
hardware. Use of the CRC allows the LAN MAC layer to guarantee a very low
probability of incorrectly delivering a corrupted packet. Crossed Pinning:
Cable configuration that allows two DTE devices or two DCE devices to