C

Caching Speeds information processing by storing information from a transaction to use for later transactions.

CAE (Common Applications Environment) Computer environment in which applications can be ported across various manufacturers' X/Open systems. The CAE contains standards for the operating system, networking protocols, languages and data management.

CAPI In Europe, CAPI (Common Application Interface) provides a common ISDN software platform for communication applications.

CAU (Controller Access Unit) A managed concentrator on a token ring network -- essentially, an intelligent version of an MAU. Handles the ring in/ring out function.

CCITT Comité Consultatif International Télégraphique et Téléphonique (Consultative Committee for International Telegraph and Telephone) An international organization that develops communications standards known as "Recommendations" for all internally controlled forms of analogue and digital communication ("Recommendation X.25" for example).

Client/Server A distributed system model of computing that brings computing power to the desktop, where users (clients) access resources held on servers.

CCS Common Channel Signaling

CDDI(Copper Distributed Data Interface) FDDI over UTP or STP copper media.

CEC Communications Engine Controller, the main processor for the NETBuilder II.

Cell relay Network transmission format that uses small packets of uniform size, called cells. The fixed-length cells can be processed and transmitted by hardware at very high speeds. Acts as a basis for SMDS Interface Protocol and ATM.

Chaining In SNA, a grouping of RUs (Request/Response Units) to aid error recovery.

Channel Aggregation Channel aggregation combines multiple physical channels into one logical channel of greater bandwidth. With BRI ISDN connections, channel aggregation would combine the two 64 K bit B channels into a single, logical 128 K bit channel.

CHAP Challenge Handshake Authentication Protocol

Cheapernet The IEEE 802.3 10BASE2 standard (or cable used in such installations). Thinnet, another term for the standard, specifies a less expensive, thinner version of traditional Ethernet cable.

CICS (Customer Information Control System) An IBM application subsystem that permits transactions entered at remote terminals to be processed concurrently by user applications.

CIR (Committed Information Rate) The transport speed the frame relay network will maintain between service locations.

Circuit-Switched Network Network that establishes a physical circuit temporarily, until it receives a disconnect signal.

CLNP (Connectionless Network Protocol) See Connectionless Network Service.

Clock Any of the sources of timing signals used in isochronous data transmission.

CMIP/CMIS (Common Management Information Protocol/Services) An OSI-based protocol that provides standard ways to manage large multivendor networks.

CMOL CMIP Over LLC

CMOS Complementary Metal-Oxide Semiconductor

CMOT (CMIP Over TCP/IP) An Internet standard defining the use of CMIP (an OSI- based protocol) over TCP for managing TCP/IP networks.

CMT (Connection Management) Process in FDDI for controlling the transition of the ring through its various operating states (off, connect, active, etc.), under the X3T9.5 specification.

CNAP Computer and Network Advisory Panel.

CO (Central Office) A local telephone company office which connects to all local loops in a given area and where circuit switching of customer lines occurs.

CO-IPX Connection Oriented IPX. A native ATM protocol based on IPX under development by Novell.

Collapsed Backbone Network architecture under which the backplane of a device such as a hub performs the function of a network backbone; the backplane routes traffic between desktop nodes and between other hubs serving multiple LANs.

Common Carrier Licensed utility that provides communications services at government-regulated rates.

Compression Reducing the size of a data set to lower the bandwidth or space required for transmission or storage.

Concentrator Device that serves as a wiring hub in star-topology network. Sometimes refers to a device containing multiple modules of network equipment.

Conditioned analog line Analog line to which devices have been added to imrpvoe the electrical signal.

Congestion Excessive network traffic.

Congestion Control In a frame relay network, the mechanisms (see BECN and FECN) designed to limit excessive traffic and provide network switches with a means of alerting the access node (e.g., a router) to slow its transmission.

Connection (or Call) Spoofing: The concept of mimicking correct responses to keep level requests alive at the local end of a temporarily broken connection is called connection (or call) spoofing. Call spoofing saves connect time charges by allowing the call to be disconnected without causing the NOS to time-out the client/host connection. It also enhances data throughput by keeping the line clear of these network administration packets.

Connectionless Communications A form of packet-switching that relies on global addresses in each packet rather than on predefined virtual circuits.

Connectionless Network Service (CLNS) Packet-switched network where each packet of data is independent and contains complete address and control information; can minimize the effect of individual line failures and distribute the load more efficiently across the network.

Connection-oriented Communications A form of packet-switching that requires a predefined circuit from source to destination to be established before data can be transferred.

Connectivity system A collection of network devices that are logically related and managed as a single entity.

Control System Control Systems measure environmental changes and perform actions in response to those changes.

CONS (Connection-Oriented Network Service) An OSI protocol for packet-switched networks that exchange information over a virtual circuit (a logical circuit where connection methods and protocols are pre-established); address information is exchanged only once. CONS must detect a virtual circuit between the sending and receiving systems before it can send packets.

Contention Network access method where devices compete for the right to access the physical medium.

Convergence When all routers on a network use a consistent perspective of the network topology.

CoreBus The chassis backbone in the NETBuilder II

COS Class Of Service

COSP Connection-Oriented Session Protocol

CPCS Common Part Convergence Sublayer

CPE (Customer Premises Equipment) Terminating equipment, such as terminals, phones and modems, supplied by the phone company, installed at customer sites and connected to the phone company network.

CPN Customer Premises Network

CSMA/CD (Carrier-Sense Multiple Access with Collision Detection) Channel access method used by Ethernet and IEEE 802.3 in which devices transmit only after finding the data channel clear for some period of time. When two devices transmit simultaneously, a collision occurs and the colliding devices delay their retransmissions for a random length of time.

CSU/DSU (Channel Service Unit/Data Service Unit) A digital interface unit that connects end user equipment to the local digital telephone loop.

Custom Signaling ISDN signaling protocols used in AT&T and Northern Telecom switches prior to the advent of the National ISDN 1 standard.

CWIS Campus-Wide Information System.