Cable
Cable is the physical transmission medium of a group of metallic conductors or optical fibers that are bound together and wrapped in a protective cover, and insulation between individual conductors/fibers and for the entire group.

Cable Range
Cable Range refers to the range of network numbers that is valid for use by nodes on an extended AppleTalk network. The cable range value can be a single network number or a contiguous sequence of several network numbers. Node addresses are assigned based on the cable range value.

Cable Router
Cable Router is a router optimized for data-over-CATV hybrid fiber-coaxial (HFC) applications. Cable router is often combined with cable modern used as an access device at home or Small Office Home Office (SOHO) for the Internet access via cable operators.

CAC: Connection Admission Control
Connection Admission Control (CAC), also known as Call Admission Control, refers to the set of actions taken by the network during the call set-up phase (or during call re-negotiation phase) in order to determine whether a connection request can be accepted or should be rejected. In the voice over IP communications, the CACs prevent an IP network from becoming clogged with traffic to the point of being unusable. When a network's capacity is consumed, admissions control mechanisms prevent new traffic from being added to the network. When calls traverse the WAN, admissions control assumes paramount importance. Within the LAN in which bandwidth is not a problem, CAC is less critical. CAC could also be a set of actions taken by each ATM switch during connection setup to determine whether a connection's requested QoS will violate the QoS guarantees for established connections. CAC also is used when routing a connection request through an ATM network.

Caching
Caching is a form of replication in which information learned during a previous transaction is used to process later transactions.

CFI: Caligare Flow Inspector
Caligare Flow Inspector (CFI) is a software tool for processing and evaluating network traffic, using network flows (netflow) export statistics sent by router. It is also a user-friendly application used for network diagnostics. It has the added ability of real time monitoring and data analysis, in which you can find and locate network traffic transmitted over the local host and local networks.

Call
A call in data networking refers to the attempted connection between a remote system and L2TP Access Concentrator (LAC). An incoming or outgoing call that is established successfully between a remote system and LAC results in a corresponding L2TP session within a previously established tunnel between the LAC and the L2TP Network Server (LNS).

Call Admission Precedence
Call Admission Precedence refers to an MPLS traffic engineering tunnel with a higher priority will, if necessary, preempt an MPLS traffic engineering tunnel with a lower priority. Tunnels that are harder to route are expected to have a higher priority and to be able to preempt tunnels that are easier to route. The assumption is that a lower-priority tunnel can find another path.

Call Agent
Call Agent, also known as a Media Gateway Controller (MGC), is the intelligent and controlling entity in an IP telephony network that handles call control in an MGCP model voice over IP network. Call agent is similar to the GateKeeper in the H.323 based on VOIP network and the SoftSwitch in the general VOIP networks.

Call Leg
Call leg is a discrete segment of a call connection in a VOIP network. A call leg is a logical connection between the router and either a telephony endpoint over a bearer channel, or another endpoint using a session protocol.

Call Setup Time
In telecommunication world, Call Setup Time is the time required to establish a switched call between users. For data communication, Call Setup Time refers to the the overall length of time required to establish a circuit-switched call between terminals; i.e., the time from the initiation of a call request to the beginning of the call message.

Campus Area Network
A campus area network (CAN) is a computer network interconnecting a few local area networks (LANs) within a university campus or corporate campus. Campus area network may link a variety of campus buildings including departments, the university library and student halls of residence. A campus area network is larger than a local area network but smaller than a metropolitan area network (MAN) or wide area network (WAN). CAN can also stand for corporate area network.

CAP: Competitive Access Provider
Competitive Access Provider (CAP) is a type telecommunication service providers that provide local telecommunications services mainly to business customers in competition with a local Bell Operating Company (BOC). Teleport and MFS are the two major CAPs operating in major metropolitan areas in the United States.

CAR: Committed Access Rate
Committed Access Rate (CAR) and distributed CAR (DCAR) is a QoS feature in routers that limits the input or output transmission rate on an interface or subinterface based on a flexible set of criteria and classifies packets by setting the IP precedence or QoS group. CAR can be used to rate-limit traffic based on certain matching criteria, such as incoming interface, IP precedence, QoS group, or IP access list criteria. CAR provides configurable actions, such as transmit, drop, set precedence, or set QoS group, when traffic conforms to or exceeds the rate limit.

CAR: Cisco Access Registrar
Cisco Access Registrar (CAR) is Cisco's RADIUS AAA solution for the service provider market. It supports service provider deployment of access services by centralizing authentication, authorization and accounting information (AAA) and by simplifying provisioning and management. CAR provides RADIUS services to DOCSIS modems for the deployment of high-speed data services in a one-way cable plant requiring telco-return for upstream data.

CARNet: Croatian Academic and Research Network
Croatian Academic and Research Network (CARNet) was founded in 1991 by the ministry of science and technology, and the institution officially came to life in 1995 when the Croatian government decreed so. CARNet's mission is to "provide the infrastructure, knowledge and the necessary resources to individuals and organizations that wish to build Croatia as an information society".

Carnivore
Carnivore is a "network diagnostic tool" or "sniffer" type of tools created by the U.S. Federal Bureau of Investigation (FBI) to assist in crime investigations. It is a software running on Windows OS. Carnivore is similar to other commercial network sniffers tools, except that Carnivore has drawn special attention, however, because of the large amount of Internet traffic it is capable of capturing. The FBI typically installs Carnivore in an ISP data center when investigating individuals suspected of federal crimes.

Catenet
Catenet is an obsolete term for a network of packet-switched communication networks interconnected via routers and gateways. It was a concept of internetworking at a time when "network" meant what is now called "local area network". The Internet is a catenet.

CATV: Cable Television
Cable Television (CATV), formerly called Community Antenna Television, is a communication network where multiple channels of programming material are transmitted to homes using broadband coaxial cable.

Cause Codes
Cause Codes indicate the reason for ISDN-call failure or completion. Typically, cause codes are ranged from 0 to 127. Cause code values of 128 and higher aren't sent over the network.

CBBS: Computerized Bulletin Board System
Computerized Bulletin Board System(CBBS) was a computer software program created by Ward Christensen to allow computer hobbyists to exchange information between one another.

CBDS: Connectionless Broadband Data Service
Connectionless Broadband Data Service (CBDS), similar to SMDS, is an ITU-T defined European packet-switched, datagram-based WAN networking technology. CBDS is used as a bearer service for BISDN, which is not widely deployed.

CBR: Constant Bit Rate
Constant Bit Rate (CBR) is one of the four QoS classes defined by the ATM Forum for ATM networks. CBR is used for connections that depend on precise clocking to ensure undistorted delivery. The other QoS services in ATM are ABR, UBR, and VBR.

CBWFQ: Class-based Weighted Fair Queueing
Class-based Weighted Fair Queueing (CBWFQ) is a queueing scheme in networking which allows traffic to be classified based on criteria, such as access control lists, input interface names, protocols, and QoS (Quality of Service) labels. CBWFQ extends the standard Weighted Fair Queueing(WFQ) functionality to provide support for user-defined traffic classes.

CCDA: Cisco Certified Design Associate
Cisco Certified Design Associate (CCDA) indicates a foundation or apprentice knowledge of network design for the Cisco Internetwork Infrastructure for the small office, home-office (SOHO) market and for medium-size organizations whose simple LAN, routed WAN, and switched LAN networks have fewer than 500 nodes. CCDA-certified professionals can design routed and switched network infrastructures involving LAN, WAN, and dial access services for businesses and organizations.

CCDP: Cisco Certified Design Professional
Cisco Certified Design Professional (CCDP) certification indicates advanced or journeyman knowledge of network design. With a CCDP, a network professional can design routed and switched networks involving LAN, WAN, and dial access services, applying modular design practices and making sure the whole solution responds optimally to the business and technical needs.

CCIE: Cisco Certified Internetwork Engineer
Cisco Certified Internetwork Engineer (CCIE) program is the highest level of Cisco Career Certification organized by Cisco since 1994. CCIE has four fields: CCIE Service Provider, CCIE Routing and Switching, CCIE Voice and CCIE Security.

CCIP: Cisco Certified Internetwork Professional
Cisco Certified Internetwork Professional (CCIP) certification provides individuals working in service provider organizations with competencies in infrastructure IP networking solutions. Cisco certified Internetwork professionals have detailed understanding of networking technologies in the service provider arena including IP routing, IP QoS, BGP, and MPLS.

CCITT: Consultative Committee for International Telegraph and Telephone
Consultative Committee for International Telegraph and Telephone (CCITT) was an international organization responsible for the development of communications standards. CCITT now became the International Telecommunications Union Telecommunication Standardization Sector (ITU-T).

CCNA: Cisco Certified Network Associates
The Cisco Certified Network Associate (CCNA) certification indicates a foundation in and apprentice knowledge of networking. CCNA certified professionals can install, configure, and operate LAN, WAN, and dial access services for small networks (100 nodes or fewer), including, but not limited to, the use of these protocols: IP, IGRP, Serial, Frame Relay, IP RIP, VLANs, RIP, Ethernet, Access Lists. The CCNA exam is the qualifying exam available to candidates pursuing a single-exam option for the Cisco Certified Network Associate CCNA certification.

CCNP: Cisco Certified Network Professional
The Cisco Certified Network ProfessionalCCNP certification indicates advanced knowledge of networks. A network professional with CCNP can install, configure, and troubleshoot local and wide area networks for enterprise organizations with networks from 100 to more than 500 nodes. The content emphasizes topics such as security, converged networks, quality of service (QoS), virtual private networks (VPN) and broadband technologies. The CCNP certification indicates knowledge of networking for big enterprises. It also confirms the ability to work in organizations whose networks have 100 to more than 500 nodes.

CCR: Commitment, concurrency, and recovery
Commitment, concurrency, and recovery (CCR) is an OSI application service element used to create atomic operations across distributed systems. CCR is used primarily to implement two-phase commit for transactions and nonstop operations in an OSI network.

CCSP: Cisco Certified Security Professional
The Cisco Certified Security Professional (CCSP) certification is the midlevel certification, which is at the same level as CCNP and CCDP. The aim of this certification is to provide professional-level recognition to network engineers in the design and implementation of Cisco secure networks. This certification provides validation of knowledge and skills in key areas of security, including firewalls, intrusion detection, VPNs, identity, and security management.

CCSRC: Cisco Subscriber Registration Center
Cisco Subscriber Registration Center is an integrated solution of Cisco Systems for data-over-cable service providers to configure and manage broadband modems, and enable and administer subscriber self-registration and activation.

CCVP: Cisco Certified Voice Professional
Cisco Certified Voice Professional (CCVP) certification recognizes the increased importance placed on IT professionals of today who are responsible for integrating voice technology into underlying network architectures. Individuals who earn a CCVP certification can help create a telephony solution that is transparent, scalable, and manageable. Earning a CCVP certification validates a robust set of skills in implementing, operating, configuring, and troubleshooting a converged IP network.

CD: Carrier Detect
Carrier Detect (CD) refers to a signal generated by modems when two modems decide that they can talk to each other. Carrier Detect indicates whether an interface is active and a call has been connected. CD remains present as long as the two modems are connected, though it can be interrupted by a call-waiting signal if one of the phone lines receives a second call.

CDDI: Copper Distributed Data Interface
Copper Distributed Data Interface (CDDI), a version of FDDI using twisted pair cables, provides data rates of 100 Mbps and uses dual-ring architecture to provide redundancy. CDDI supports distances of about 100 meters from desktop to concentrator. The CDDI standard is officially named as the Twisted-Pair Physical Medium-Dependent (TP-PMD) standard. It is also referred to as the Twisted-Pair Distributed Data Interface (TP-DDI).

CDF: Channel Definition Format
Channel Definition Format (CDF) is an application similar to RSS based on XML used in conjunction with Microsoft Active Channel and Smart Offline Favorites technologies. CDF is used to define a website's content and structure and to "push" applications on the World Wide Web.

CDF: Cutoff Decrease Factor
Cutoff Decrease Factor CDF, a term in the ATM networking, controls the decrease in ACR (Allowed Cell Rate) associated with CRM (missing RM cell count). For ATM ABR traffic, CDF effects the time rate of change of the ACR. This value effects TCP round trip time calculations, which in turn effects TCP throughput.

CDR: Call Detail Record
Call Detail Record (CDR), a term used in both PSTN and VOIP systems, is a telephone call record written to a database for use in postprocessing activities. A typical CDR includes the origination and destination addresses of the call, the time the call started and ended, the duration of the call, the time of day the call was made and any toll charges that were added through the network or charges for operator services, among other details of the call. CDRs are primiarily used for billing and network analysis.

CDV: Cell Delay Variation
Cell Delay Variation (CDV), also referred to as cell jitter, is the variation of cell transfer delay in an ATM network, the variation in cell delay through the network. CDV is induced by buffering and cell scheduling. CDV is a QoS delay parameter associated with CBR and VBR service in the ATM network.

CDVT: Cell Delay Variation Tolerance
Cell Delay Variation Tolerance (CDVT) is a QoS parameter in ATM network for managing traffic that is specified when a connection is set up. In CBR transmissions, CDVT determines the level of jitter that is tolerable for the data samples taken by the PCR.

CE router: Customer Edge router
Customer Edge router, also known as CE router, is a router located at the customer premise that interfaces to a service provider edge (PE) router.

Cell
Cell or ATM cell is the basic data unit for ATM switching and multiplexing. Each ATM cell consists of a 5-byte header and 48 bytes of payload. The header of cells contain identifiers that specify the data stream to which they belong.

Cell Block
Cell blocks are a sequence of N cells transmitted consecutively on a given ATM connection. A cell block will normally correspond to the number of information cells transmitted between successive OAM cells.

Cell Payload Scrambling
Cell Payload Scrambling is a technique using an ATM switch to maintain framing on some medium-speed edge and trunk interfaces. Scrambling is designed to randomize the pattern of 1s and 0s carried in ATM cells or in the physical layer frame. Randomizing the digital bits can prevent continuous, non-variable bit patterns; in other words, long strings of all 1s or all 0s. Several physical layer protocols rely on transitions between 1s and 0s to maintain clocking.

Cell Relay
Cell Relay is a network technology of statistically multiplexing fixed-length packets, i.e. cells, to transport data between computers or kinds of network equipment. It is an unreliable, connection-oriented packet switched data communications method. Because cells are fixed-length, they can be processed and switched in hardware at high speeds. Cell relay is the basis for many high-speed network protocols including ATM, IEEE802.6, and SMDS. Cell relay is used for time-sensitive traffic such as voice and video.

CELP: Code excited linear prediction compression
Code excited linear prediction compression is a compression algorithm used in low bit-rate voice encoding, which is used in ITU-T Recommendations G.728, G.729, G.723.1.

CEN: European Committee for Standardization
European Committee for Standardization (CEN) is a non-profit organization which has a mission to promote voluntary technical harmonization in Europe in conjunction with worldwide bodies and its partners in Europe. The organization works in partnership with Comite Europeen de Normalisation Electrotechnique (CENELEC) and ETSI (European Telecommunications Standards Institute) to accomplish its goals.

CENELEC: Comite Europeen de Normalisation Electrotechnique
Comite Europeen de Normalisation Electrotechnique (CENELEC) is the European Committee for Electrotechnical Standardization. It was set up in 1973 and was officially recognised as the European Standards Organisation in its field by the European Commission in Directive 83/189 EEC. CENELEC works with 40,000 technical experts from 19 EC and EFTA countries to publish standards for the European market.

CER: Cell Error Ratio
Cell Error Ratio (CER), a term in the ATM network, is the ratio of transmitted cells that have errors to the total cells sent in a transmission for a specific period of time.

CERFnet: California Education and Research Federation Network
California Education and Research Federation Network (CERFnet) is a TCP/IP network, based in Southern California, that connects hundreds of higher-education centers internationally while also providing Internet access to subscribers. CERFnet was founded in 1988 by the San Diego Supercomputer Center and General Atomics, and is funded by the NSF.

CERN: European Laboratory for Particle Physics
European Laboratory for Particle Physics (CERN) is a famous European Laboratory for Particle Physics. It is also the birthplace of many Internet technologies including the World Wide Web.

CES: Circuit Emulation Service
Circuit Emulation Service (CES) is an ATM service which enables users to multiplex or to concentrate multiple circuit emulation streams for voice and video with packet data on a single high-speed ATM link without a separate ATM access multiplexer. CES is typically implemented on ATM switches, but it can be implemented on ATM edge devices (such as routers) as well. CES is mostly used for communication between non-ATM telephony devices (like PBXs, TDM, and channel banks) or video devices (such as CODEC) and ATM devices, or via an ATM uplinks.

CGI: Common Gateway Interface
The Common Gateway Interface (CGI) is a standard for external gateway programs to interface with information servers such as HTTP servers. CGI scripts are commonly used on Web sites to achieve customised results. Generally, when the visitor performs some action, such as filling in a form or clicking on a link, the server executes a script using information input by the visitor. This allows the appearance or behaviour of the Web site to be customised for that visitor.

Chaining
Chaining is a concept in the IBM Systems Network Architecture (SNA). SNA chaining allows terminal messages to be chained, and lets large messages be split into smaller parts while still logically treating the multiple message as a single message.

Channel Bonding
Channel bonding, sometimes also called redundant array of independent network interfaces (RAIN), is an arrangement in which two or more network interfaces on a host computer are combined for redundancy or increased throughput. On Ethernet interfaces, channel bonding requires assistance from both the Ethernet switch and the host computer's operating system, which must "stripe" the delivery of frames across the network interfaces in the same manner that I/O is striped across disks in a RAID array.

Channel-Attached
Channel-Attached refers to peripheral devices directly attached to the computer via data channels (input/output channels) or bus. The term is used in contrast with devices that are reached remotely over a network, which is known as network attached.

Channelized
Channelized in a telecommunications environment means that the line that communications have been transmitted over contains more than one message thread, separated in some fashion. Typical channelization methods include packetizing, frequency differentiation, time division multiplexing (TDM). For example, Channelized T1 sub-divide the 1.44 Mbps bandwidth into 24 channels of 64 Kbps each.

Channelized E1
Channelized E1 refers to that an E1 access link of at 2.048 Mbps is subdivided into 30 B-channels and 1 D-channel of 64 Kbps each. Channelized T1 and channelized E1 can be configured for ISDN PRI, synchronous serial, and asynchronous serial communications.

Channelized T1
Channelized T1, also known as fractional T1, refers to that an access link operating at 1.544 Mbps is subdivided into 24 channels (23 B-channels and 1D-channel) of 64 Kbps each. The individual channels or groups of channels connect to different destinations. Channelized T1 and channelized E1 can be configured for ISDN PRI, synchronous serial, and asynchronous serial communications.

Chargen: Character Generation
Character Generation (Chargen) is a service via TCP that sends a continual stream of characters until stopped by the client. When Chargen is served via UDP, the server sends a random number of characters each time the client sends a datagram.

Chat Script
Chat Script is a string of text that defines the login "conversation" that occurs between two systems. Consists of expect-send pairs that define the string that the local system expects to receive from the remote system and what the local system should send as a reply.

Cheapernet
Cheapernet, also known as thinnet or thinwire, refers to the IEEE 802.3 10Base2 standard or the cable specified in that standard. Cheapernet is 0.2 inches in diameter and has 50 ohms of electromagnetic impedance.

Checksum
Checksum is a method for checking the integrity of transmitted data. A checksum is an integer value computed from a sequence of octets taken through a series of arithmetic operations. The value is recomputed at the receiving end and is compared for verification. Almost every protocol has a checksum field as part of protocol header or trailer.

Chernobyl Packet
A Chernobyl packet, a term named in memory of the April 1986 nuclear accident at Chernobyl in Ukraine, is a network packet that induces a broadcast storm and/or network meltdown. The typical scenario involves an IP Ethernet datagram that passes through a gateway with both source and destination Ether and IP address set as the respective broadcast addresses for the subnetworks being gated between.

Child Peer Group
Child Peer Group refers to a peer group subordinate to another peer group which is the parent peer group. The parent peer group contains the logical group node representing the child peer group.

Choke Packet
Choke Packet refers to the packets sent to a transmitter to tell it that congestion exists and that it should reduce its sending rate.

Christmas Tree Packet
A Christmas tree packet, also known as a "Kamikaze" packet, nastygram, and lamp test segment, is a packet with every single option set for whatever protocol that is in use. The term probably derives from a fanciful image of each little option bit being represented by a different-colored light bulb, all turned on, as in, "the packet was lit up like a Christmas Tree."

Churn
Churn refers to the situation that many subscriber additions and then un-subscription. If the churn ratio is high for a service provider, it is not good, because that the cost is typically high to get a customer to sign in a service and the service provider has a problem to keep customers.

CIA: Classical IP over ATM
Classical IP over ATM (CIA), defined in IETF RFC 2225, is a specification for running IP over ATM in a manner that takes full advantage of the features of ATM.

CICNet
CICnet was a network connect the CIC (Committee of Institutional Cooperation) member institutes, which is a consortium of 12 research universities, including the 11 members of the Big Ten Conference and the University of Chicago. Founded in 1988, CICNet was a part of the NSF NET and was funded by the NSF until the NSFNET dissolved in 1995.

CICS: Customer Information Control System
Customer Information Control System (CICS) is an IBM application subsystem allowing transactions entered at remote terminals to be processed concurrently by user applications.

CID: Craft Interface Device
Craft Interface Device (CID) is a terminal- or PC-based interface that enables the performance of local maintenance operations.

CID: Channel ID
Channel ID (CID) designates the Frame Relay subchannel ID for Voice over Frame Relay.

CIDR: Classless Inter-Domain Routing
Classless Inter-Domain Routing (CIDR), sometimes known as supernetting, is an addressing scheme under IPv4 for the Internet which allows for more efficient allocation of IP addresses than the old Class A, B, and C address scheme. The Internet is currently a mixture of both "CIDR-ized" addresses and old Class A, B and C addresses. Almost all new routers support CIDR and the Internet authorities strongly encourage all users to implement the CIDR addressing scheme.

CIP : Channel Interface Processor
Channel Interface Processor (CIP) is a channel attachment interface for Cisco 7000 series routers. The CIP is used to connect a host mainframe to a control unit, eliminating the need for a front end processor (FEP) for channel attachment.

CIR: Committed Information Rate
Committed Information Rate (CIR), one of parameters in a Service Level Agreement (SLA), is the data transfer rate for an individual virtual circuit (VC) in an ATM or Frame Relay network, for which the provider commits to deliver. The provider may send any data in excess of this rate for this VC if its network has capacity at the time. This choice typically affects the price of each VC.

Circuit
A circuit is a communications path between two or more points among a network. A physical circuit is actually a wire or a part of a wire which connects two computer or network devices for permanently dedicated communications. A virtual circuit may be a temporarily established logic connection between two network devices for communications within certain time limit.

Circuit Group
Circuit group is a group of associated serial lines that link two bridges. If one of the serial links in a circuit group is in the spanning tree for a network, any of the serial links in the circuit group can be used for load balancing. This load-balancing strategy avoids data ordering problems by assigning each destination address to a particular serial link.

Circuit Steering
Circuit Steering, also known as port snooping, is a mechanism used by some ATM switches to eavesdrop on a virtual connection and copy its cells to another port where an ATM analyzer is attached.

Circuit-level Inverse Multiplexing
Circuit-level Inverse Multiplexing is a method of inverse multiplexing in which the inverse multiplexer slices the data stream into equal portions, and transmits each portion over an available circuit. The receiving end adjusts for network-induced delay and reassembles the data packets into their proper order. The AIM and BONDING protocols define how circuit-level inverse multiplexing works. Applications that require transparent digital circuits, such as videoconferencing, nailed-up backup and overflow, and bulk file transfer applications, use circuit-level multiplexing.

Cisco IOS
Cisco IOS (abreviated from Internetwork Operating System) is the operating system used on Cisco Systems routers and some network switches (those which do not use CatOS). It is a multitasking operating system and provides kernel services such as process scheduling as well as the command line interface and routing software.

CNR: Cisco Network Registrar
Cisco Network Registrar(CNR) is a Cisco software product that provides IP addresses, configuration parameters, and DNS names to DOCSIS cable modems and PCs, based on network and service policies. CNR also provides enhanced TFTP server capabilities, including the generation of DOCSIS cable modem configuration files.

Cisco ONP: Cisco Optical Network Planner
The Cisco Optical Network Planner(ONP) is the network planning tool designed by Cisco Systems, Inc. ONP is designed for use with Cisco ONS 15900 Series Wavelength Router network elements to optimize available optical network bandwidth.

CiscoWorks
CiscoWorks is a Cisco product to help users manage a Cisco-based network. CiscoWorks is a web-based suite of tools developed largely in Java. Older versions used client-side Java heavily; the latest version uses more HTML and improves data sharing among tools. CiscoWorks suite consists of various components such as:
CiscoWorks Resource Manager Essentials
CiscoWorks CiscoView
CiscoWorks Common Services
CiscoWorks Campus Manager
CiscoWorks Device Fault Manager (DFM)
CiscoWorks Internetwork Performance Monitor
CiscoWorks IP Telephony Manager

CW2000: CiscoWorks 2000
CiscoWorks 2000 (CW2000) is a bundle of network management products from Cisco. CW2000 contains better versions of the major features of the old CiscoWorks, and is easier to use.

Cisco WRM: Cisco Wavelength Router Manager
Cisco Wavelength Router Manager (Cisco WRM) is an element management system designed by Cisco for use with the Cisco ONS 15900 Series Wavelength Router.

Cisco WW TAC: Cisco's World-Wide Technical Assistance Center
Cisco's World-Wide Technical Assistance Center (WW TAC) is the user front of all Cisco software and hardware maintenance and support services. Contact the Cisco WW TAC for help with installation and testing, performance, training, documentation, equipment repair Return Material Authorization (RMA) service, and equipment specifications.

CiscoView
CiscoView, a module in the CiscoWorks, is a GUI-based device-management software application that provides dynamic status, statistics, and comprehensive configuration information for Cisco internetworking devices. In addition to displaying a physical view of Cisco device chassis, CiscoView also provides device monitoring functions and basic troubleshooting capabilities, and can be integrated with several leading SNMP-based network management platforms.

CIX: Commercial Internet Exchange
Commercial Internet eXchange (CIX) is a connection point between the commercial Internet service providers. The CIX Association (also abreviated as CIX), now renamed to U.S. INTERNET SERVICE PROVIDER ASSOCIATION (US ISPA), is a non-profit association of Internet service providers that promotes the public data internetworking services industry. US ISPA provides a forum for exchanging information about internetworking services. US ISPA also encourages technical research and development that benefits its members, suppliers, and customers of public data communication services. US ISPA also promotes and administers policies and standards among its members.

Clara Network
Latin American Cooperation of Advanced Networks (Clara) network is a network connecting many of latin America's academic computer networks. The CLARA organization is responsible for the implementation and management of a network infrastructure that will interconnect the national academic networks of several Latin American countries. With several universities and research centers connected to RedCLARA -the CLARA network-, many projects that suffered with the lack of an adequate infrastructure to support communication and collaboration are then able to advance.

Classful Routing
Classful Routing is an old routing logic that first matches the Class A, B, or C network in the routing table. If the network number is matched, and then the correct subnet number matching a packets destination IP address is not found, any existing default route is not used. Classful Routing has a very poor IPv4 address utilization. The classful routing has been replaced by Classless Inter-Domain Routing (CIDR), which has much better IPv4 address utilization.

Classful Routing Protocol
Classful Routing Protocols are the protocols supporting the old classful routing using class A, B, and C as IP addressing scheme. The mostly used classful routing protocols include RIP v1, IGRP, EGP and BGP3. These protocol are mostly replaced by classless routing protocols.

Classless Routing Protocol
Classless routing protocols are the protocols supporting Classless Inter-Domain Routing (CIDR), a newer scheme of IPv4 addressing. The mostly used classful routing protocols include RIP v2 v3 and v4, EIGRP, OSPF, IS-IS and BGP4.

Clear Channel
Clear channel is a channel in which the full bandwidth (eg, 64 kbps) is used for transmission; no portion of the channel is set aside for control,framing or signaling. Clear channel uses out-of-band signaling (as opposed to in-band signaling), so the channel's entire bit rate is available.

ClearCase
ClearCase, developed by Rational software and now owned by IBM, provides life cycle management and control of software development assets. With integrated version control, automated workspace management, parallel development support, baseline management, and build and release management, ClearCase provides the capabilities needed to create, update, build, deliver, reuse and maintain business-critical assets.

ClearDDTS
ClearDDTS is a Distributed Defect Tracking System developed by Rational software and now owned by IBM. ClearDDTS provides change request management for UNIX development, specifically designed to track and manage defects and enhancement requests found during development and quality assurance testing. ClearDDTS Can be tightly integrated with software configuration management products, such as Rational ClearCase, to effectively manage change throughout the software development lifecycle.

ClearQuest
ClearQuest, developed by Rational software and now owned by IBM, enables better insight, predictability and control of the software development process. Through flexible workflow management and defect and change tracking across the application life cycle, Rational ClearQuest helps to automate and enforce development processes, manage issues throughout the project life cycle, and facilitate communication between all stakeholders across the enterprise.

CLEI: Common Language Equipment Identifier
Common Language Equipment Identifier (CLEI) is the standard code used by suppliers in telecom insutry to identify equipment parts and system configurations. CLEI is a registered trademark of Bellcore (now Telcordia).

CLI : Command-line Interface
Command-line Interface (CLI) is an interface that allows the user to interact with the operating system by entering commands and optional arguments. The UNIX operating system and DOS provide CLIs. Now CLIs are mostly replaced by GUI - Graphic User Interface.

CLI: Command Language Interpreter
Command Language Interpreter (CLI) is the basic Cisco IOS configuration and management interface. It has a type of simple character Command-line Interface. The IOS CLI provides a fixed set of multiple-word commands -- the set available is determined by the "mode" and the privilege level of the current user. "Global configuration mode" provides commands to change the system's configuration, and "interface configuration mode" provides commands to change the configuration of a specific interface.

Client/Server Computing
Client/Server Computing, also called distributed computing/processing, refers to a computing architecture with distributed computing (processing) network systems in which transaction responsibilities are divided into two parts: client (front-end) and server (back-end). Both client and server can be software programs or actual computing devices. The client/server computing is based on the Client-server model.

Client-server model
Client-server model, also often written as client/server model, is a network architecture which separates the client such as a graphical user interface from the server such as database host. Each instance of the client software can send requests to a server or application server. There are many different types of servers; some examples include: a file server, terminal server, or mail server. While their purpose varies somewhat, the basic architecture remains the same. This model allows clients and servers to be placed independently on nodes in a network, possibly on different hardware and operating systems appropriate to their function.

CLNS: Connectionless Network Service
Connectionless Network Service (CLNS) is a type of network service at the layer 3 of the OSI model. CLNS does not require a circuit to be established before data is transmitted. CLNS routes messages to their destinations independently of any other messages. The mostly used protocol for the connectionless network service is UDP - User Datagram Protocol. ISO has protocols providing this service: Connectionless Netwwork service Protocol (CLNP).

CLP: Cell Loss Priority
Cell Loss Priority (CLP) is a field in the ATM cell header that determines the probability of a cell being dropped if the network becomes congested. When CLP = 0, it is insured traffic, which is unlikely to be dropped. When CLP = 1, it is the best-effort traffic, which might be dropped in congested conditions in order to free up resources to handle insured traffic.

CLR: Cell Loss Ratio
Cell Loss Ratio (CLR) is a field in ATM cell header, which indicates the ratio of discarded cells to cells that are transmitted successfully. CLR can be set as a QoS parameter when a connection is set up.

CLS: Cisco Link Services
Cisco Link Services (CLS) is a front-end for a variety of data-link control services.

CLSI: Cisco Link Services Interface
Cisco Link Services Interface refers to the messages that are exchanged between CLS and data-link users, such as APPN, SNA service point, and DLSw+.

Cluster
Cluster, in computer networking, refers to a number of different implementations of shared computing resources. Typically, a cluster integrates the resources of two or more computing devices (that could otherwise function separately) together for some common purpose. For example, a Web server farm with a collection of networked Web servers, each with access to content on the same site, functions as a cluster conceptually.

Cluster Controller
Cluster Controller, typically an IBM 3174 or 3274 device in the SNA, is a device with certain intelligence that provides the connections for a cluster of terminals to a data link. In the IBM SNA, cluster controller is actually a programmable device that controls the input/output operations of attached devices.

CMI : Coded Mark Inversion
Coded Mark Inversion (CMI) is an ITU-T line coding technique specified for STS-3c transmissions and DS-1 systems.

CMS: Call Management System
Call Management System (CMS) is a reporting package used on ACDs and PBXs made by Avaya. Avaya CMS is an optional database, administration and reporting application designed for enterprises that receive a large volume of telephone calls and have complex contact center operations. Avaya CMS provides an administrative interface to the automatic call distribution (ACD) feature of the DEFINITY Server, enabling your contact center managers to generate reports, administer ACD parameters and monitor call activities to help determine the most efficient service possible for your customers.

CMS: Configuration Management System
Configuration Management System (CMS) is an application that provides management of security features and assurances through control of changes made to hardware, software, firmware, documentation, test, test fixtures and test documentation of an automated information system, throughout the development and operational life of a system. CMS can be part of a large network management solution or a stand-alone system.

CMT: Connection ManagemenT
Connection ManagemenT (CMT) is primarily responsible for the maintenance of physical connections to the FDDI ring. CMT handles the transition of the ring through its various states (off, active, connect, and so on), as defined by the ANSI X3T9.5 specification.

CMTS: Cable Modem Termination System
Cable Modem Termination System (CMTS) is a specially designed router or a bridge for data networking. CMTS is located at the headend of service providers and used to aggregate traffic from multiple Cable Modems and then communicate with the backbone network.

CO FRAD: Central office frame relay access device
Central office frame relay access device (CO FRAD) refers to the frame relay access device residing in service provider's central office and can be used to build permanent virtual circuits for point-to-point, backup or global service. The other type of FRAD is the Managed FRAD, which means the FRAD is provided, installed and managed by service provider at customer premises.

COCF: Connection-Oriented Convergence Function
Connection-Oriented Convergence Function (COCF) is a function on DQDB network that converts incoming data from connectionless network to outgoing data over a connection-oriented network. Connection-Oriented Convergence Functions (COCFs) use the enhanced Queued Arbitrated (QA) functions which are necessary to support connection-oriented services.

Co-SysOp
A Co-SysOp is a super user who is granted certain admin privileges on a BBS, a wiki or some online forum systems. Generally, they would help validate users and monitor discussion forums and content posting.

Codec: Coder-decoder
In the telecommunication world, Codec is a combination of two words: Coder-decoder, which is an analog-to-digital (A/D) and digital-to-analog (D/A) converter for translating the signals from the outside world to digital, and back again. For example, integrated circuit device typically uses pulse code modulation to transform analog signals into a digital bit stream and digital signals back into analog signals.

Codec: Compression/Decompression
In computing world, Codec refers to compression/decompression, which typically is an algorithm or specialized computer program that encodes or reduces the number of bytes consumed by large files and programs. Files encoded with a specific codec require the same codec for decoding. MPEG is a type of codec algorithms.

Coding
In computer hardware, coding is the process of converting information obtained on a subject or unit into coded values (typically numeric) for the purpose of data storage, management, and analysis. While in software, coding means implement a programing logic using a specific language such as C or C++. In cryptography, coding refers to the act of writing in code or cipher.

Collapsed Backbone
Collapsed Backbone refers to a nondistributed backbone in which all network segments are interconnected by way of an internetworking device. A collapsed backbone might be a virtual network segment existing in a device such as a hub, a router, or a switch.

Collision
Collision refers to the situation when there are two or more simultaneous transmissions on a common signal channel such as half-duplex Ethernet or shared Ethernet. An Ethernet network uses Carrier Sense Multiple Access/Collision Detect (CSMA/CD) to allow devices to take turns using the signal carrier line. When a device wants to transmit, it checks the signal level of the line to determine whether someone else is already using it. If a line is in use, the device waits and retries. If the line is not in use, the device transmits.

Collision Avoidance
Collision Avoidance is a MAC method of avoiding collisions in a network. In a network such as wireless LAN, station listens to a network in order to avoid collisions, unlike Collision Detection that deals with network transmissions once collisions have been detected. Collision Avoidance contributes to network traffic because, before any real data is transmitted, it has to broadcast a signal onto the network in order to listen for collision scenarios and to tell other devices not to broadcast. Collision avoidance (CSMA/CA) is often used in wireless LAN.

Collision Detection
Collision Detection is a MAC method of detecting simultaneous transmissions in a network. In a Enternet, each transmitting workstation will detect the collision and delay retransmission in order to avoid a repeat of the collision. Workstations can tell that a collision has taken place if they do not receive a response within a certain time frame or if no acknowledgment is received from the server. While transmitting, stations continue to listen for incoming signals (collisions) and emit a jamming signal to notify all other stations of the collision. Collision detection (CSMA/CD) is used in wired Ethernet LAN.

Collision Domain
A collision domain is a logical area in a computer network, in particular in the Ethernet network, where data packets can "collide" with one another. The more collisions in a network the less efficient it is because stations need to re-transmit when collision happens. A collision domain can be a single segment of Ethernet cable in shared-media Ethernet, or a single Ethernet hub in twisted-pair Ethernet, or even a whole network of hubs and repeaters.

Colocation
Colocation refers to the provision of space for a customer's communications equipment on the service providers premises. For example, a Web site owner could place its own computer servers on the premises of the Internet Service Provider (ISP). Or an ISP could place their network routers on the premises of the company offering switching services with other ISPs.

Common Carrier
Common Carrier is a licensed, private utility company that supplies communication services to the public at regulated prices. The term differs from private carrier, which operates solely for the benefit of one entity and does not offer services to the general public.

Communication Controller
Communication controller is a network device which manages data input and output to a host computer or computer network. It may be front-end mainframe interfaces or network devices such as multiplexors, bridges, and routers. Communication controller converts parallel computer data to serial data for transmission over communication lines and perform all the necessary control functions, error checking, and synchronization. In the IBM SNA, the communication controllers are 3745 and 3746, which can be used in the TCP/IP environment as well.

Communication Server
Communication Servers are specially designed computer servers that provide access to resources on the network for users not directly attached to the network or that permits network users to access external resources not directly attached to the network. Communication servers typically connect asynchronous devices to a LAN or WAN through network and terminal emulation software.

Communications Line
Communications Line refers to the physical link (such as wire or a telephone circuit) that connects one or more devices to one or more other devices.

Community String
Community String, a concept used in the SNMP-based network management system, is a text string that acts as a password and is used to authenticate messages sent between a management station and a router containing a SNMP agent. The community string is sent in every packet between the manager and the agent.

Companding
Companding, also known as compansion, comes from the combination of compressing and expanding, which is a method of reducing the effects of a channel with limited dynamic range. The use of companding allows signals with a large dynamic range to be transmitted over facilities that have a smaller dynamic range capability. Companding reduces the noise and crosstalk levels at the receiver.

Composite Clock
Composite Clock, also called composite timing, is a bipolar timing signal containing 64 khz bit-clock and 8 khz byte-clock frequencies.

Composite Timing
Composite Timing, also called composite clock, is a bipolar timing signal containing 64 khz bit-clock and 8 khz byte-clock frequencies.

Compound Option
Generally speaking, a Compound Option is an option where the underlying is another option. In DOCSIS for data-via-cable communications, a compound option composes of a number of sub-options. For example, options 4 and 24 are compound options.

Compression
Compression is a technique that reduces the quantity of bandwidth or bits required to encode a block of information. Compression saves transmission time and capacity, and can free up storage space on in-demand data lines. Compressed data can be compromised in quality, but the advantages of bandwidth savings are frequently worth the trade-off.

Computer Cluster
A computer cluster is a group of logically connected computers that work together closely so that in many respects it can be viewed as though it were a single computer. Clusters maybe connected through fast local area networks or logically connected via wide area network. Clusters are usually deployed to improve speed and/or reliability over that provided by a single computer, while typically being much more cost-effective than single computers of comparable speed or reliability.

CONF: Configuration Failure
Configuration Failure refers to the situation that failure message is received during the process of configuring a hardware or software system manually or automatically.

Configuration Direct VCC
Configuration Direct VCC (Virtual Channel Connection ) is a bi-directional point-to-point VCC set up by an LEC (LAN Emulation Client) to an LES (LAN Emulation Server) in an ATM network. It is one of three control connections defined by Phase 1 LANE. The other two are control distribute VCC and control direct VCC.

Configuration Management
Configuration Management is one of five categories of network management, which refers to setting, changing, collecting and restoring information about network devices. A network configuration management system allows network admin to take control of network changes, to simplify the job of managing networks and to fix configuration errors quickly.

Configuration register
Configuration register is a 16-bit, user-configurable value used by routers, with which you can set specific system parameters that determines how the router functions during initialization. The configuration register can be stored in hardware or software. In hardware, the bit position is set using a jumper. In software, the bit position is set by specifying a hexadecimal value using configuration commands.

Configuration Tool
Configuration Tool is a software utility with a GUI which allows user to configure some network element and their services.

Congestion
Congestion refers to the situation that the traffic in the network or part of the network is in excess of network capacity. When congestion happens, transmission will slow down and some packets may get dropped.

Congestion Avoidance
Congestion Avoidance is a mechanism by which an ATM network controls the traffic entering the network to minimize delays. To use resources most efficiently, lower-priority traffic is discarded at the edge of the network if conditions indicate that it cannot be delivered.

Congestion Collapse
Congestion Collapse refers to the condition in which the retransmission of frames in an ATM network results in little or no traffic successfully arriving at the destination. Congestion collapse frequently occurs in ATM networks composed of switches that do not have adequate and effective buffering mechanisms complimented by intelligent packet discard or ABR congestion feedback mechanisms.

Connectionless
Connectionless describes communications between two network end points in which a message can be sent from one end point to another without prior arrangement. The device at one end of the communication transmits data to the other, without first ensuring that the recipient is available and ready to receive the data. The device sending a message simply sends it addressed to the intended recipient. If there are problems with the transmission, it may be necessary to resend the data several times.

Connectionless Mode Transmission
Connectionless mode transmission is transmission in which each packet is prepended with a header containing a destination address sufficient to permit the independent delivery of the packet without the aid of additional instructions. A packet transmitted in a connectionless mode is frequently called a datagram, such as the packet communication using UDP(User Datagram Protocol).

Connectionless Protocol
Connectionless Protocols are the protocols that enable connectionless services in a network. The Internet Protocol (IP) and User Datagram Protocol (UDP) are the most popular connectionless protocols.

Connectionless Routing
In connectionless routing, each packet is treated separately, making its way through the network independently. Each individual packet may take different routes through the network depending on the type of routing protocol used and the amount of traffic on the network. As the packets travel along varying routes, they may not necessarily arrive at the designated location in sequence.

Connection-Oriented
Connection-oriented refers to transmitting data reliably in which the devices at the end points use a protocol to establish an end-to-end connection before any data is sent. Once the connection is established, the devices pass information back and forth through the connection without regard to their physical addresses. The connection may be physical or virtual and it guarantees that data will arrive in the proper sequence.

Connection-oriented mode transmission
Connection-oriented mode transmission is a transmission in which each packet is prepended with a header containing a destination address sufficient to permit the independent delivery of the packet without the aid of additional instructions. A packet transmitted in a connectionless mode is frequently called a datagram. In connection-oriented communication, the stations about to exchange data first need to declare towards each other that they want to do so. This is called "establishing a connection". A connection is sometimes defined as a logical relationship between the peers exchanging data.

Connection-oriented Protocol
Connection-oriented Protocol is designed for connection-oriented services in data communication in which the devices at the end points use a preliminary protocol to establish an end-to-end connection before any data is sent. Connection-oriented protocol service is sometimes called a "reliable" network service, because it guarantees that data will arrive in the proper sequence. Transmission Control Protocol (TCP) is a connection-oriented protocol.

CONS: Connection-oriented network service
Connection-oriented network service is a network service that establishes logical connections between end users before transferring information. This service is for reliable data transfer to ensure data arrives in proper sequence.

Console
In a network management frame work using SNMP (Simple Network Management Protocol), Console is a software program that has the capability of interacting with remote agents, including examining or changing the values of the data objects in the agent's Management Information Base (MIB).

Constraint-based Routing
Constraint-based routing is a QoS (Quality of Service) routing technique that is used with the development of MPLS (Multiprotocol Label Switching). Constraint-based routing enables a demand driven, resource reservation aware, routing paradigm to co-exist with current topology driven hop by hop through Internet IGPs

Contention
Contention is an access method in which network devices compete for permission to access the physical medium.

Context Aware Network
Context aware network is a form of computer network that is a synthesis of the properties of dumb network and intelligent computer network architectures, which combines the best of both network models. A context aware network is designed to allow for customization and application creation while at the same time ensuring that application operation is compatible not just with the preferences of the individual user but with the expressed preferences of the enterprise or other collectivity which owns the network.

Control Direct VCC
Control Direct VCC (Virtual Channel Connection ) is a bidirectional VCC set up by an LEC (LAN Emulation Client) to an LES(LAN Emulation Server) in an ATM network. It is one of three control connections defined by Phase 1 LANE. The other two are configuration direct VCC and control direct VCC.

Control Messages
Control messages are typically signalling messages that provide the control of setup, maintenance, and teardown of sessions and tunnels.

CAN: Controller Area Network
Controller Area Network (CAN) is a multicast shared serial bus standard for connecting electronic control units (ECUs). CAN was specifically designed to be robust in noisy environments and can utilize a differential balanced line like RS-485. It can be even more robust against noise if twisted pair wire is used. Although initially created for automotive purposes (as a vehicle bus), nowadays it is used in many embedded control applications (e.g., industrial) that may be subject to noise.

Convergence
Network convergence refers to using packet network to conduct voice (telephony), video and data services, and phasing out the traditional PSTN (Public-Switched Telephone Network) gradually. The migration process from multiple separate data and voice to finally a completely converged packet network carrying both voice and data services may take decades to finish. The driving forces behind such convergence are cost saving, operation efficiency and new service deployment.

Cookie
Cookie is a piece of information sent by a Web server to a Web browser that the browser is expected to save and send back to the Web server whenever the browser makes additional requests of the Web server.

Coral Content Distribution Network
Coral Content Distribution Network, an open source and peer-to-peer content distribution network, is designed to mirror web content. Coral is designed to use the bandwidth of volunteers to reduce the load on websites and other providers of web content.

CORBA: Common Object Request Broker Architecture
Common Object Request Broker Architecture (CORBA) is an architecture and specification for creating, distributing, and managing distributed program objects in a network. It allows programs at different locations and developed by different vendors to communicate in a network through an "interface broker." CORBA was developed by a consortium of vendors through the Object Management Group (OMG). CORBA is now endorsed by both ISO and X/Open as the standard architecture for distributed components.

Core Gateway
Core gateway is the primary routers and gateways operated by the Internet Network Operations Center. Core gateway forms a central part of Internet routing in that all groups must advertise paths to their networks from a core gateway.

Core Router
Core router is the router at the backbone in a packet-switched star topology. It serves as the single pipe through which all traffic from peripheral networks must pass on its way to other peripheral networks.

COS: Class of Service
Class of Service (COS), also known as Type of Service (ToS), is one type of the techniques or methods used to deliver Quality of Service (QoS) in a network. CoS is a way of classifying and prioritizing packets based on application type (voice, video, email, file transfer, transaction processing etc., the type of user (VIP or normal etc.) or other ways of classifications. A "first class" priority label is assigned to data applications - such as mission-critical data transactions, or video or voice transmissions - which require faster turnaround, while a lower-priority label is assigned to less time-sensitive traffic, such as e-mail and Web surfing.

COS: Corporation for Open Systems
Corporation for Open Systems (COS) is an organization that promulgates the use of OSI protocols through conformance testing, certification, and related activities.

CoS Management
CoS Management refers to the management of Class of Services (Cos) in a network, which is essential for delivering the required QoS to all applications. This enables network managers to refine connections to meet specific application needs. CoS management includes operations such as per-VC queuing, per-VC rate scheduling, multiple CoS queuing, and egress queuing.

COSINE: Cooperation for Open Systems Interconnection Networking in Europe
Cooperation for Open Systems Interconnection Networking in Europe (COSINE) is European project financed by the EC to build a communication network between scientific and industrial entities in Europe. The project ended in 1994.

Cost value
Cost value, sometimes called path cost, is a measure, typically based on hop count, media bandwidth, or other measures, that is assigned by a network administrator and used to compare various paths through an internetwork environment. Routing protocols use cost values to determine the most favorable path to a particular destination: the lower the cost, the better the path.

Continuity Test
In electronics, a continuity test is the checking of an electric circuit to see if current flows (that it is in fact a complete circuit). A continuity test is performed by placing a small voltage (wired in series with an LED or noise-producing component such as a piezoelectric speaker) across the chosen path. If electron flow is inhibited by broken conductors, damaged components, or excessive resistance, the circuit is "open". In telecommunication, continuity test is a requirement of the SS7 protocol specifications, which. tests the bearer channels' status using either loopback or tone detection and generation.

Count To Infinity
Count To Infinity is a problem that can occur in routing algorithms that are slow to converge, in which routers continuously increment the hop count to particular networks. Typically, some arbitrary hop-count limit is imposed to prevent this problem.

CP: Control Point
Control Point, in SNA networks, is an element that identifies the APPN networking components of a PU 2.1 node, manages device resources, and provides services to other devices. In APPN, CPs can communicate with logically adjacent CPs by way of CP-to-CP sessions.

CPCS: Common Part Convergence Sublayer
Common Part Convergence Sublayer (CPCS) is one of the two sublayers of any ATM Adaptation Layer (AAL). The CPCS is responsible for preparing data for transport across the ATM network. CPCS wraps the user-service data units in a header and trailer which contain information used to provide the services required. The information in the header and trailer depends on the class of information to be transported but will usually contain error handling and data priority preservation information.

CPE: Customer Premises Equipment
Customer Premises Equipment (CPE) is a type of terminating equipment, such as terminals, telephones, and modems, supplied by the telephone company, installed at customer sites, and connected to the telephone company network. CPEs may also refer to any telephone equipment residing on the customer site regardless who supplied them.

CPI-C: Common Programming Interface for Communications
Common Programming Interface for Communications (CPI-C) is a platform-independent API developed by IBM and used to provide portability in APPC applications in the SNA based network.

CPNIE: Called party number information element
Called party number information element (CPNIE) is a type of Information Elements in the ISDN messages defined in ITU-T Q.931.

CPNIE: Calling Party Number Information Element
Calling Party Number Information Element (CPNIE) is a type of Information Elements in the ISDN messages defined in ITU-T Q.931.

CPS: Cells Per Second
Cells Per Second (CPS) is a unit of measure used for ATM switch capacity and speed.

CPSIE: Called Party Subaddress Information Element
Called Party Subaddress Information Element is a type of Information Element in the ISDN messages defined in ITU-T Q.931.

CQ: Custom Queuing
Custom queuing is a QoS method to provide a guaranteed level of service for all traffic. Customer queuing allows a customer to reserve a percentage of bandwidth for specified protocols. Customers can define up to 10 output queues for normal data and an additional queue for system messages such as LAN-keep-alive messages (routing packets are not assigned to the system queue).

Crankback
Crankback is a mechanism used by ATM networks when a connection setup request is blocked because a node along a selected path cannot accept the request. In this case, the path is rolled back to an intermediate node, which attempts to discover another path to the final destination using GCAC.

CRC: Cyclic Redundancy Check
Cyclic Redundancy Check (CRC), also called "cyclic redundancy code", is a method of insuring data integrity where a calculation is performed using the binary representation of the data itself as the basis of the calculation. The CRC is the numerical result of this calculation and is held separately from the data. The integrity of the data is checked by calculating a new CRC. If the two CRCs match, then there is a high degree of confidence that the data has not changed.

CREN: Corporation for Research and Educational Networking
Corporation for Research and Educational Networking (CREN) is an organization merged from BITNET and CSNET. On January 7 2003, CREN's members decided to dissolve the organization.

CRF: Concentrator Relay Function
Concentrator Relay Function (CRF), also known as Token Ring Concentrator Relay Function (TrCRF), is a logical grouping of ports. Within the TrCRF, source-route switching is used for forwarding based on either MAC addresses or route descriptors. Frames can be switched between ports within a single TrCRF. A TrCRF has two global parameters: a ring number and a parent TrBRF identifier.

CRF: Cell Relay Function
Cell Relay Function (CRF) is the basic function that an ATM network performs in order to provide a cell relay service to ATM end-stations.

CRF: Connection Related Function
Connection Related Function (CRF), a term used by Traffic Management, refers to a point in a network or a network element where per connection functions are occurring. This is the point where policing at the VCC or VPC level may occur.

CRL: Certificate Revocation List
Certificate Revocation List (CRL) is a type of data structure that enumerates digital certificates that have been invalidated by their issuer prior to when they were scheduled to expire.

CRM: Cell Rate Margin
Cell Rate Margin (CRM) is a measure of the difference between the effective bandwidth allocation and the allocation for sustainable rates in cells per second. CRM is one of three link attributes exchanged using PTSPs to determine the available resources of an ATM network.

Cross Talk
Cross Talk refers to the interfering energy transferred from one circuit to another, or the unwanted information from one channel to "spill over" into an adjacent channel.

CRP: Customer Routing Point
Customer Routing Point (CRP) is an AT&T's terminology for third-party processors that accept routing requests from the CCSS7 network.

CRS: Cell Relay Service
Cell Relay Service (CRS) is a carrier service which supports the receipt and transmission of ATM cells between end users in compliance with ATM standards and implementation specifications.

CRV: Call Reference Value
Call Reference Value (CRV) is the number carried in all Q.931 (I.451) messages that provides an identifier for each ISDN call.

CS: Convergence Sublayer
Convergence Sublayer (CS) is one of the two sublayers of the AAL CPCS in an ATM architecture, which is responsible for padding and error checking. PDUs passed from the SSCS and appended with a 8-byte trailer (for error checking and other control information) and padded, if necessary, so that the length of the resulting PDU is divisible by 48. These PDUs are then passed to the SAR sublayer of the CPCS for further processing.

CSA: Canadian Standards Association
Canadian Standards Association is the Canadian agency that certifies products that conform to Canadian national safety standards.

CS-ACELP: Conjugate Structure Algebraic Code Excited Linear Prediction
Conjugate Structure Algebraic Code Excited Linear Prediction (CS-ACELP) is the CELP voice compression algorithm providing 8 kbps, or 8:1 compression, standardized in ITU-T Recommendation G.729.

CSD Box: Control Signal Distribution Box
Control Signal Distribution Box (CSD Box) is the bulkhead splitter box that distributes the clock and control system signals within a system.

CSI: Called Subscriber Identification
Called Subscriber Identification (CSI) is an identifier whose coding format contains the telephone number from a remote fax terminal.

CSNET: Computer Science Network
Computer Science Network (CSNET) was an internetwork consisting primarily of universities, research institutions, and commercial concerns. CSNET merged with BITNET to form CREN, which was dissolved in 2003.

CSNP: Complete Sequence Number PDU
Complete Sequence Number PDU (CSNP) is the PDU sent by the designated router in an OSPF network to maintain database synchronization.

CSO: Composite Second Order Beat
Composite Second Order Beat (CSO) is the peak of the average level of distortion products due to second-order non-linearities in cable system equipment.

CTB: Composite Triple Beat
Composite Triple Beat (CTB) is the peak of the average level of distortion components due to third-order non-linearities in cable system equipment.

CTD: Cell Transfer Delay
Cell Transfer Delay (CTD), a term used in the ATM networking, is the elapsed time between a cell exit event at the source UNI and the corresponding cell entry event at the destination UNI for a particular connection. The CTD between the two points is the sum of the total inter-ATM node transmission delay and the total ATM node processing delay.

CTI: Computer Telephony Integration
Computer Telephony Integration (CTI) is the technology that links the computer, telephone and other services such as voice messaging and fax. CTI improves the handling of the customer relationship. For example, customer details can be on screen while an agent answers the call.

CTS: Clear To Send
Clear To Send (CTS) is a signalling message transmitted from the data communications equipment (DCE) indicating to the data terminal equipment (DTE) that it may begin data transmission. For example, a networking equipment such as IEEE 802.11 wireless station may send a CTS in response to an RTS (Request to Send) message. The CTS message silences all wireless stations in its vicinity to avoid collision and enables the sender of the RTS message to begin data transfer.

CTS: Common Transport Semantic
Common Transport Semantic (CTS), an IBM initiative to reduce the number of protocols on networks, provides a single API for developers of network software and enables applications to run over APPN, OSI, or TCP/IP.

CUDI: Coorporacin Universitaria para el Desarrollo de Internet
Coorporacin Universitaria para el Desarrollo de Internet (CUDI) is a non-profit consortium to build and operate a Mexican high-performance backbone network for research and education, Internet-2 Mexico.

Cut-Through
Cut-Through is a method of switching where only the header of a packet is read before it is forwarded to its destination.

Cut-through Packet Switching
Cut-through Packet Switching, also known as on-the-fly packet switching, streams data through a switch so that the leading edge of a packet exits the switch at the output port before the packet finishes entering the input port. A device using cut-through packet switching reads, processes, and forwards packets as soon as the destination address is looked up, and the outgoing port determined. The other type of switching technology is called store-and-forward packet switching.

Cut-through Switch
Cut-through switch is a packet switch wherein the switch starts forwarding that frame (or packet) before the whole frame has been received, normally as soon as the destination address is processed. A cut-through switch can achieve the lowest forwarding delays, but it propagates errors from one LAN to another, because errors can only be detected at the end of each frame. In other words, this technique reduces latency through the switch, but decreases reliability.

CV: Coding Violation
Coding Violation (CV) is the occurrence of transmission bit error(s) in paths and lines, as detected by examining a redundancy check code embedded within the signal format. CV also refers to the performance parameter, which is the count of transmission error detections at line, path, and section levels.

Cybercafe
Cybercafe, also known as Internet cafe, is a place where one can use a computer with Internet access for a fee, usually per hour or minute; sometimes, one can have unmetered access with a pass for a day or month, etc. It may or may not serve as a regular cafe as well, with food and drinks being served.

Cyberspace
Cyberspace is a term originated by author William Gibson in his novel Neuromancer to describe the "world" of computers and the society that gathers around them. Cyberspace is currently used to describe the whole range of information resources available through computer networks, especially the Internet.