Glossary

BRI u Basic Rate Interface ISDN interface composed of two B Channels and one D Channel for circuit- switched communication of voice, video, and data.

BSP u Board Support Package A board support package consists of documentation and software used to configure and install a specific operating system on a specific product.

BUS u Broadcast and Unknown Server Multicast server used in ELANs that is used to flood traffic addressed to an unknown destination and to forward multicast and broadcast traffic to the appropriate clients.

CAM u Content Addressable Memory Memory that is accessed based on its contents, not on its memory address.

CBR u Constant Bit Rate QoS class defined by the ATM Forum for ATM networks. CBR is used for connections that depend on precise clocking to ensure undistorted delivery.

CCS u Common Channel Signaling Signaling system used in telephone networks that separates signaling information from user data. A specified channel is exclusively designated to carry signaling information for all other channels in the system.

COM u Communication or Communications

CompactPCI u CompactPCI is an adaptation of the Peripheral Component Interconnect (PCI) Specification for industrial and/or embedded applications requiring a more robust mechanical form factor than desktop PCI. CompactPCI uses industry standard mechanical components and high performance connector technologies to provide an optimized system intended for rugged applications. CompactPCI provides a system that is electrically compatible with the PCI Specification, allowing low cost PCI components to be utilized in a mechanical form factor suited for rugged environments. CompactPCI is an open specification supported by the PICMG (PCI Industrial Computer Manufacturers Group), which is a consortium of companies involved in utilizing PCI for embedded applications.

CPCS u Common Part Convergence Sublayer An abstract ATM protocol API defined by the ATM Forum. It forms the boundary interface between the purely software implemented higher layer ATM protocols and the segmentation and reassembly process controlled by hardware.

CPM u Communication Processing Module

CRC4 u Cyclic Redundancy Check. Error-checking technique in which the frame recipient calculates a remainder by dividing frame contents by a prime binary divisor and compares the calculated remainder to a value stored in the frame by the sending node.

CS u Convergence Sublayer One of the two sublayers of the AAL CPCS, which is responsible for padding and error checking. PDUs passed from the SSCS are appended with an 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.

CSU u Channel Service Unit A component that terminates a digital circuit, such as T1. A CSU assures compliance to FCC regulations and preforms some line-conditioning functions.

DChannel u Data Channel Full-duplex, 16-kbps (BRI) or 64-kbps (PRI) ISDN channel.

DCE u 1. Data Communications Equipment (EIA expansion). 2. Data Circuit-terminating Equipment (ITU-T expansion). Devices and connections of a communications network that comprise the network end of the user-to-network interface. The DCE provides a physical connection to the network, forwards traffic, and provides a clocking signal used to synchronize data transmission between DCE and DTE devices. Modems and interface cards are examples of DCE.

DLCI u Data-Link Connection Identifier Value that specifies a PVC or SVC in a Frame Relay network. In the basic Frame Relay specification, DLCIs are locally significant (connected devices might use different values to specify the same connection). In the LMI extended specification, DLCIs are globally significant (DLCIs specify individual end devices).

DMA u Direct Memory Access The transfer of data directly into memory without supervision of the pro- cessor. The data is passed on the bus directly between the memory and another device.

DPRAM u Dual Port Random Access Memory

DS1 u Digital Signal level 1 Framing specification used in transmitting digital signals at 1.544-Mbps on a T1 facility (in the United States) or at 2.108-Mbps on an E1 facility (in Europe).

DS3 u Digital Signal level 3 Framing specification used for transmitting digital signals at 44.736 Mbps on a T3 facility.

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