C-LAN cable CACP
CAD CADD CAE
CAI Call For Vote(CFV) call priority
call setup time CAM CAMMU
Carbon Copy CARNet Carrier
CAS CASE Catenet
CATV CBDS CBIOS
CBLT CCA CCD
CCIRN CCITT CCR
CCS CD CBLT
CDP CD-R CD-ROM
cell cell relay cellular radio
CEMM centrex CEPT
CERFnet CERN CERT
CESNet CGA CGS
chaining Channel channel attached
Channel Bank CHAOSnet CHAP
Character Characteristic Impedance
checksum choke packet CICS
Circuit Switching CISC
Cisco 3000 Cisco 4000 Cisco Bus
Cisco Bus controller Cisco Works CIX
ClariNews class of service CLI
Client client-server computing
Client-Server Model CLNP CLNS
Clock CLTP Cluster
cluster controller CMI CMIP
CMIP/CMIS CMNS CMOS
CMOT CMS CMT
CNI CO coaxial cable
CODEC coding common carrier
common channel signal. communication communic. controller
communication line communication server community
companding Composite Link Compression
configurat. management Congestion Connection Tools
Connection-Oriented Connectionless CONP
CONS console contention
Control Characters Control Signals convergence
conversation Core Gateway Core Network
COSINE count to infinity CP
CPE CPT CPU
Cracker CRC CREN
CSC/3 CSC/4 CSC-C2CTR
CSC-CCTL2 CSC-ENVM CSC-FCIT
CSC-MC CSC-MC+ CSC-MCI
CSC-MEC CSC-R16 CSC-SCI
CSDN CSLIP CSMA/CD
CSNET CSNP CSO
CSU CTS CU-SeeMe
CUA Current Loop CWIS
Cyberspace cycles per second Cyclic Redundancy Check
C-LAN Frame Relay public
network in Italy.
cable A transmission medium
of wires or optical fibers wrapped in a protective cover.
CACP (Central Arbitration
CAD (Computer-Aided Design).
CADD (Computer-Aided Design
CAE (Computer-Aided Engineering).
CAI (Computer-Aided Instruction).
Call For Votes (CFV) Initiates
the voting period for a Usenet newsgroup. At least one (occasionally two
or more) email address is customarily included as a repository for the
votes. See Newsgroup Creation for a full description of the Usenet
voting process. [Source: ZEN]
call priority Priority
assigned to each origination port in circuit-switched systems. This priority
also defines which calls can or cannot be placed during a bandwidth reservation.
call setup time The
time required to establish a switched call between DTE devices.
CAM (Computer-Aided Manufacturing).
Common access method.
CAMMU (CAche/Memory Management
Carbon Copy A copy of a message
which all persons on the Cc: list receive. Recipients of the message can
see who else it has been circulated to.
A Croatian Internet service.
Carrier A continuous
signal at a fixed frequency capable of being modulated with a second (Information
CAS (Column-Address Strobe)
(Communications Applications Specification).
CASE (Computer-Aided Software
Catenet A network in
which hosts are connected to networks with varying characteristics, and
the networks are interconnected by gateways (routers). The Internet is
an example of a catenet. See: IONL.[Source:
CATV (CAble TeleVision).
Formerly called Community Antenna Television, a communication system where
multiple channels of programming material are transmitted to home using
broadband coaxial cable.
Broadband Data Service). Synonym for SMDS.
High-speed, packet-switched, datagram-based WAN
CBIOS (Compatibilty BIOS).
CBLT (Character Block Transfer).
CCA (Conceptual Communication
CCD (Charge-Coupled Device).
High-density memory devices whose semiconductor units are linked in such
a way that the electrical output of one unit becomes the input of the next.
CCIRN (Coordinating Committee
for Intercontinental Research Networks). A committee that includes the
United States FNC and its counterparts in North America and Europe. Co-chaired
by the executive directors of the FNC and the European Association of Research
Networks (RARE), the CCIRN provides a forum for cooperative planning among
the principal North American and European research networking bodies. See
also: Federal Networking Council, RARE.
CCITT (Consultative Committee
International for Telegraphy and Telephony). This organization is now part
of the International Telecommunications Union and is responsible for making
technical recommendations about telephone and data communications systems.
Every four years CCITT holds plenary sessions where they adopt new standards;
the most recent was in 1992. Recently, the ITU reorganized and CCITT was
renamed the ITU-TSS. See also: International
Telecommunications Union - Telecommunications Standards Sector. [Source:
CCR (Commitment, Concurrency,
and Recovery). An OSI application service
element used to create atomic operations across distributed systems. Used
primarily to implement two-phase commit for transactions and [Source: RFC1208]
CCS (Common Channel
Signaling). A signaling system used by many telephone networks that separates
signaling information from user data.
CD (Carrier Detect). An interface
signal defined in EIA RS-232-C
from terminal (DTE) towards the data
communication equipment (DCE), to indicate
that the data channel has been switched to the communication equipment.
The equivalent CCITT (ITU)
definition is circuit Nr. 108.2, defined in V.24.
CD-I (Compact Disk, Interactive).
CDMA (Code Division Multiple
CDP (Conditional Di-Phase).
A digital encoding technique wich is a variant of Manchester encoding,
but is insensitive to polarity of wires (wires in a pair can be crossed).
CD-R (Compact Disc, Recordable).
CD-ROM (Compact Disc Read-Only
cell The basic unit
for ATM switching and multiplexing. Each
cell consists of a five-byte header and 48 bytes of payload.
cell relay Network
technology based on the use of small, fixed-size packets, or cells. Cells
contain identifiers that specify the data stream to which they belong.
Because the cells are fixed length, they can be processed and swiched in
hardware at very high speeds. Cell relay is the basis for many high-speed
network protocols, including IEEE 802.6,
DQDB, the SMDS
Interface Protocol, and ATM.
cellular radio A technology
that uses radio transmissions to access the phone-company network. Service
is provided in a particular cell (area) by a low-power transmitter.
CEMM (Compaq Expanded Memory
centrex An improved
PBX that also provides direct
inward dialing and automatic number identification of the calling PBX.
Refers to a specific AT&T telephone system product.
CEPT (Conference Europeene
des Postes et Telecommunications). An association of the 26 Eureopean PTTs
that recommends communicatiomn specifications to the CCITT.
Education and Research Foundation Network). TCP/IP-based network in Southern
California connecting many higher-education centers designed to advance
science and education through communications.
Particle physics institute located in Geneva, Switzerland, originators
of the World Wide Web.
CERT (Computer Emergency Response Team)
The CERT was formed by ARPA in November 1988 in response to
the needs exhibited during the Internet worm incident. The CERT charter
is to work with the Internet community to facilitate its response to computer
security events involving Internet hosts, to take proactive steps to raise
the community's awareness of computer security issues, and to conduct research
targeted at improving the security of existing systems. CERT products and
services include 24-hour technical assistance for responding to computer
security incidents, product vulnerability assistance, technical documents,
and tutorials. In addition, the team maintains a number of mailing lists
(including one for CERT Advisories), and provides an anonymous FTP server,
at "cert.org", where security-related documents and tools are archived.
The CERT may be reached by email at "firstname.lastname@example.org" and by telephone at
+1-412-268-7090 (24-hour hotline). See also: Advanced
Research Projects Agency, Worm.
Academic network in Czech Republic
CGA (Color Graphics Adapter).
CGS Compact Gateway
Server. Cisco two-slot modular bridge/router
chaining SNA concept
in which Rus (request/response
units) are grouped together for the purpose of error recovery.
Channel A path for electrical
transmission between two or more points. Also called a link, line, circuit
channel attached Pertaining
to attachment of devices directly by data channels (I/O channels) to a
Channel Bank Equipment
that connects multiple voice channels into a high speed link, by performing
voice digitization and Time Division Multiplexing. Generally voice is converted
to a 64 kbps signal (24 channels into 1.544 Mbps in the U.S.; 30 channels
into 2.048 Mbps in Europe).
CHAOSnet A network
protocol developed at MIT and uses primarily by the artificial intelligence
CHAP Challenge Handshake
Authentication Protocol. A security feature that prevents unauthorized
access to devices running the feature (such as Cisco communication servers).
CHAP is only supported on lines using PPP
Character Any coded
representation of a letter, digit, or special symbol.
Impedance The termination impedance of an electrically uniform
term used to refer to the IEEE 802.3
10Base2 standard on the cable specified in that standard. Thinnet,
which is also used to describe this standard, specifies a less expensive,
thinner version of Ethernet cable.
checksum A computed
value which is dependent upon the contents of a packet. This value is sent
along with the packet when it is transmitted. The receiving system computes
a new checksum based upon the received data and compares this value with
the one sent with the packet. If the two values are the same, the receiver
has a high degree of confidence that the data was received correctly. [Source:
choke packet Packet
sent to a transmitter to tell it that congestion exists and that it should
reduce its sending rate.
CICS (Customer Information
Control System). An IBM application subsystem allowing transactions entered
at remote terminals to be processed currently by user applications.
CIDR (Classless Inter-domain
Routing). A proposal, set forth in RFC
1519, to allocate IP addresses so as to allow the addresses to be aggregated
when advertised as routes. It is based on the elimination of intrinsic
IP network addresses; that is, the determination of the network address
based on the first few bits of the IP address. See also: IP
address, network address,
supernet. [Source: RFC1983]
circuit A communication
link between two or more points.
Circuit Switching A
communications paradigm in which a dedicated communication path is established
between two hosts, and on which all packets travel. The telephone system
is an example of a circuit switched network. See also: Connection-Oriented,
Switching. [Source: RFC1392]
CISC (Complex Instruction-Set
Cisco 3000 Cisco two-port
multiprotocol router with Flash memory in a fixed-configuration system.
Uses a 20-Mhz 68EC030 microprocessor.
Cisco 4000 Cisco router/bridge
with NVRAM and Flash memory three interface modules, and a 68030 CPU that
runs at 25 Mhz.
Cisco Bus Half-a-gigabit-per-second
proprietary bus technology developed and marketed for high-speed switching
by Cisco Systems, Inc.
Cisco Bus controller See
Cisco Works A comprehensive
set of SNMP-based applications
for monitoring, administering, and mananging Cisco internetworks.
CIX (Commercial Internet
eXchange). The Commercial Internet eXchange Association is a
non-profit, 501(c)6, trade association of Public Data Internetwork
service providers promoting and encouraging development of the public data
communications internetworking services industry in both national and international
markets.[Source: CIX Association]
Also: (Compulink Information eXchange). Is an online
community of about 15-20k users (we call ourselves cixen) of all kinds.
ClariNews The fee-based
Usenet News feed available from ClariNet Communications. [Source: ZEN]
COS (Class of service).
An indication of how an upper-layer protocol wants a lower-layer protocol
to treat its messages. In subarea routing, COS definitions are used by
subarea nodes to determine the optimal route to establish a given session.
A COS definition comprises a virtual route number and a transmission priority
field. Also called type of service.
CLI (Command Line Interpreter).
Client A computer system
or process that requests a service of another computer system or process.
A workstation requesting the contents of a file from a file server is a
client of the file server. See also: Client-Server
Model, Server. [Source: NNSC]
client-server computing Term
used to describe distributed processing (computing) network systems in
which transaction responsibilities are divided into two parts: client (front
end) and server (back end). Both terms (client and server) can be applied
to both software programs or actual computing devices. See also PDU
A common way to describe the paradigm of many network protocols.
Examples include the name-server/name-resolver relationship in DNS and
the file-server/file-client relationship in NFS. See also: Client,
Name System, Network File System.
CLNP (Connectionless Network
Protocol). The OSI protocol for providing the OSI Connectionless Network
Service (datagram service). CLNP is the OSI equivalent to Internet IP,
and is sometimes called ISO IP. [Source: RFC1208]
CLNS (Connectionless Network
Service). The model of interconnection in which communication takes place
without first establishing a connection. Sometimes (imprecisely) called
datagram. E.g.: LANs,
Internet a href="GlossarioI.html#IP">IP and OSI CLNP,
UDP, ordinary postcards. [Source:
Clock A shorthand term
for the source(s) of timing signals used in synchronous transmission.
CLTP (Connectionless Transport
Protocol). Provides for end-to-end Transport data addressing (via Transport
selector) and error control (via checksum), but cannot guarantee delivery
or provide flow control. The OSI equivalent of UDP.
Cluster A configuration
in which two or more terminals are connected to a single line or single
cluster controller Generally,
an intelligent device that provides the connections for a cluster of terminals
to a data link. In SNA, a programmable device that controls the I/O operations
of attached devices. Typically, an IBM 3174 or 3274 device.
CMI (Coded Mark Inversion).
A CCITT line coding technique specified
for the fourth-level CCITT multiplex signal. Also used in DS-1
CMIP (Common Management
Information Protocol). The OSI network management protocol.[Source: RFC1208]
CMIP/CMIS (Common Management
Information). Protocol/Common Management Information Services. OSI network
management protocol/service interface created and standardized by ISO for
managing heterogeneous networks.
Network Service). Extends local X.25 switching to a variety of media (Ethernet,
CMOS (Complementary Metal-Oxide
CMOT (CMIP Over TCP) An
effort to use the OSI network management protocol to manage TCP/IP networks.
CMS (Conversational Monitor
System). IBM system.
CMT (Connection Management).
An FDDI process that handles the transition
of the ring through its various states (off, active, connect, and so on),
as defined by the X.3T9.5
CNI (Coalition for Networked
Information). A consortium formed by American Research Libraries, CAUSE,
and EDUCOM (no, they are not acronyms) to promote the creation of, and
access to, information resources in networked environments in order to
enrich scholarship and enhance intellectual productivity. [Source: RFC1983]
CO (Central Office).
A local telephone company office to swich all local loops in a given area
connect and in which circuit switching of subscriber lines occurs.
coaxial cable A cable
consisting of a hollow outer cylindrical conductor that surrounds a single
inner wire conductor. Two types of coaxial cable are currently used for
local area networks: 50-ohm cable, which is used for digital signaling,
and 75-ohm cable, which is used for analog signaling and high-speed digital
A device that typically uses pulse code modulation to transform analog
voice into a digital bit stream and vice versa.
coding Electrical techniques
used to convey binary signals.
common carrier A licensed,
private utility company that supplies communication services to the pubblic
at regulated prices.
common channel signaling Exclusive
use of a specified channel to carry signaling information for all other
channels in the group.
communication controller In
SNA, a subarea node (such as an IBM 3745 device) that contains an NCP.
communications line The
physical link (such as wire or a telephone circuit) that connects one or
more devices to another.
communication server A
communications proocessor that connects asynchronous devices to a LAN
or WAN through network and terminal
community In SNMP,
a logical group of managed devices and NMSs
in the same administrative domain.
companding A contraction
derived from the opposite processes called compression and expansion. Part
of the PCM process whereby analog signal sample values are logically rounded
to discrete scale-step values on a nonlinear scale. The decimal step number
is then coded in its binary quivalent prior to transmission. The processes
is reserved at the receiving terminal using the same nonlinear scale.
Composite Link The
line or circuit connecting a pair of multiplexers or concentrators, carrying
Compression Any of
several techniques that reduce the number of bits required to represent
information in data transmission or storage, thereby conserving bandwidth
The world's largest provider of Internet and Online Services.
Multiplexer). A device which divides a data channel into two or more channels
of lower average speed. The concentrator dynamically allocates channel
space according to demand in order to maximize throughput.
configuration management One
of five categories of network management defined by ISO
for management of OSI networks. Configuration
management subsystems are responsible for detecting and determining the
network's state. See also accounting
management, fault manegement,
performance management, and security
occurs when the offered load exceeds the capacity of a data communication
path. [Source: RFC1983]
Connection Tools One
of the three types of communications tools. A connection tool determines
the type of connection that is established between your Macintosh and the
The data communication method in which communication proceeds
through three well-defined phases: connection establishment, data transfer,
connection release. TCP is a connection-oriented protocol. See also: Circuit
Switching, Connectionless, Packet
Switching, Transmission Control Protocol.
data communication method in which communication occurs between hosts with
no previous setup. Packets between two hosts may take different routes,
as each is independent of the other. UDP is a connectionless protocol.
See also: Circuit Switching, Connection-Oriented,
Packet Switching, User
Datagram Protocol. [Source: RFC1983]
Network Protocol). An OSI protocol
providing connection-oriented operation to upper-layer protocols. See also
Network Service). The model of interconnection in which communication proceeds
through three well-defined phases: connection establishment, data transfer,
connection release. Examples: X.25,
Internet TCP and OSI TP4,
ordinary telephone calls.
console Data Terminal
Equipment (DTE) through which commands
are entered into a host.
Contention A condition
arising when two or more data stations attempt to transmit at the same
time using the same channel.
Control Characters In
communications, any extra transmitted characters used to control or facilitate
data transmission (for example, characters associated with polling, framing,
synchronization, error checking, or message delimiting).
Control Signals Signals
passing between one part of a communications systems and another (such
or RI), as part of a mechanism for controlling the system.
convergence The ability
of (and speed with which) a group of internetworking devices running a
specific routing protocol agree on the internetwork's topology after a
change in network topology.
conversation In SNA,
an LU 6.2 session between two transaction
Core Gateway Historically,
one of a set of gateways (routers) operated by the Internet Network
Operations Center at Bolt, Beranek and Newman (BBN).
The core gateway system formed a central part of Internet routing in that
all groups must advertise paths to their networks from a core gateway.
Core Network Combination
of switching offices and transmission plant connecting switching offices
together. In the U.S. local exchange Core Networks are linked by several
competing Interexchange networks; in the rest of the world (now) the Core
Network extends to national boundaries. [Source: ADSL
COS (Corporation for Open Systems) A
vendor and user group for conformance testing, certification, and promotion
of OSI products.[Source: RFC1208]
COSINE (Cooperation for Open Systems
Interconnection Networking in Europe) A program sponsored by
the European Commission, aimed at using OSI to tie together European research
count to infinity A
problem that can occur in routing algorithms that are slow to converge,
in which routers sequentially increment the hop count to particular networks
until (typically) some arbitrary limit is imposed.
CP Control Point. Element
in an SNA device that manages device resources. It can provide services
to other devices.
CPE (Customer Promises
Equipment). Terminating equipment, suchg as terminals, phones, and modems,
supplied by the phone company, installed at customer sites, and connected
to the phone company network.
CPT Cisco Protocol
Translator. Cisco product, based on its C chassis, that translates (acts
as a gateway) between diverse protocols.
CPU (Central Processing Unit).
A logic chip that executes instructions passed to it.
Cracker A cracker is
an individual who attempts to access computer systems without authorization.
These individuals are often malicious, as opposed to hackers, and have
many means at their disposal for breaking into a system. See also: Hacker,
Computer Emergency Response Team, Trojan
Horse, Virus, Worm.
CRC (Cyclic Redundancy Check).
A number derived from a set of data that will be transmitted recalculating
the CRC at the remote end and comparing it to the value originally transmitted,
the receiving node can detect some types of transmission errors. [Source:
CREN (Corporation for Research
and Educational Networking). This organization was formed in October 1989,
when a Bitnet and CSNET (Computer +
Science NETwork) were combined under one administrative authority. CSNET
is no longer operational, but CREN still runs Bitnet. See also: Bitnet.
transfer of energy from one circuit to another. Crosstalk typically occurs
between adjacent circuits.
CSA (Carrier Serving Area).
Also (Confederate States of America).
CSC-1R Cisco single-port
68030-based Token ring interface
card that operates at 4 Mbps or 16 Mbps.
CSC-2R Cisco dual-port
68030-based Token ring interface
card that operates at 4 Mbps or 16 Mbps.
CSC/3 Cisco 30-Mhz
MC 68020-based processor card. See also route
CSC/4 Cisco MC 68040-based
(25 Mhz) processor card with 16 MB of DRAM see also route
CSC-C2CTR Cisco high-speed
Token Ring interface card with two or four ports.
and faster ciscoBus controller a bitslice processor that administers activity
and controls traffic and switching across the high-speed ciscoBus.
CSC-ENVM Cisco environmental
monitor card for the AGS+ chassis that monitors power supply voltage and
temperature conditions to ensure appropriate system shutdown in the event
of anomalous system conditions (high voltage or temperature)
CSC-FCIT Cisco FDDI
interface card with translational bridging capability.
CSC-MC Cisco memory
card containing 32 kilobytes of memory. The CSC-MC supplies nonvolatile
configuration information to the Cisco router.
CSC-MC+ Cisco memory
card containing NVRAM to store
configuration information and Flash
EPROM technology to store operating system software.
CSC-MCI Cisco Multiport
Communications Interface. A Cisco router interface card that provides zero,
one, or two Ethernet ports and zero, one, or two serial ports.
CSC-MEC Cisco interface
card with either two, four, or six Ethernet ports.
CSC-R16 Cisco interface
card supporting either 4-or16-Mbps Token Ring.
CSC-SCI Cisco interface
card supporting one, two, or four synchronous serial interface ports with
transmission rates of up to 4 Mbps each.
CSDN (Circuit Switched Data
Network). As opposed to PSDN.
Serial Line Internet Protocol). A protocol that minimizes traffic and speed
throughput on SLIP lines.
CSMA/CD (Carrier Sense
Multiple Access with Collision Detection). The access method used by local
area networking technologies such as Ethernet.[Source:RFC1208]]
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.
See Bitnet.. [Source:RFC1208]
CSNP (Complete Sequence
Number). PDUs sent by the designated
router in an OSPF network to maintain
CSU (Channel Service Unit).
User-owned equipment installed on customer premises at the interface to
phone company lines to terminate a DDS
or T1 circuit. CSUs provide network protection
and diagnostic capabilities.
CSO (Computing Services Office).
The phonebook facilities within gopher are provided by a piece of software
originating from the University of Illinois at Urbana-Champaign (UIUC).
This software is commonly known as the CSO Nameserver (CSO stands for Computing
Services Office which is the name of the department which originally provided
the software) and is made up of 2 parts forming a client-server application.
The server part of it is called 'qi' (query interpreter); until gopher
arrived on the scene, sites using CSO phonebooks usually used a client
called 'ph' (short for phonebook) to interrogate the phonebook database.
Also: (Central Services Organization)
CTS (Clear To Send). A modem
interface control signal from the data communications equipment (DCE)
indicating to the data terminal equipment (DTE)
that it may begin data transmission.
"See you, See me," CU-SeeMe is a publicly available videoconferencing program
developed at Cornell University. It allows anyone with audio/video capabilites
and an Internet connection to videoconference with anyone else with the
same capabilities. It also allows multiple people to tie into the same
videoconference. [Source: RFC1983]
CUA (Common User Access).
Current Loop Method
of data transmission. A mark (binary "1") is represented by current on
the line, and a space (binary "0") is represented by the absence of current.
CWIS (Campus Wide Information
System). A CWIS makes information and services publicly available on campus
via kiosks, and makes interactive computing available via kiosks, interactive
computing systems and campus networks. Services routinely include directory
information, calendars, bulletin boards, databases. [Source: RFC1983]
Cyberspace A term
coined by William Gibson in his fantasy novel Neuromancer to describe the
"world" of computers, and the society that gathers around them. [Source:
cycles per second See
EUnet in Cyprus.
CYMK (Cyan, Yellow,