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Wild Packets - Networking terms Category: Agriculture and Industry > Networking terms Date & country: 24/02/2017, USA Words: 1152

CPI-C
Common Programming Interface for Communications. Platform-independent API developed by IBM and used to provide portability in APPC applications. See also APPC.

CPS
Cells per second.

CPU
Central Processing Unit. The main processor in the computer'sconfiguration that handles processing tasks or directs auxiliaryprocessors (coprocessors) to perform them.

CPU bound
A computing activity or network interaction whose speed is limitedby the speed at which the CPU can perform the necessary computing tasks.

Crash
An abrupt termination or computing activity caused by an error. Inmany instances, the computer becomes completely unusable andmust be restarted before activity can resume.

CRC
Cyclic Redundancy Check. A method of insuring data integritywhere a calculation is performed using the binary representationof the data itself as the basis of the calculation. The CRC is thenumerical result of this calculation and is held separately from thedata. The integrity of the data is checked by calculating a newCRC. If the two CRC's match, then there is a high degree of confidence that the data has not changed.

CREN
Corporation for Research and Educational Networking. The result of a merger of BITNET and CSNET. CREN is devoted to providing Internet connectivity to its members, which include the alumni, students, faculty, and other affiliates of participating educational and research institutions, via BITNET III. See also BITNET, BITNET III, and CSNET.

Crosstalk
In electronic signaling, an error condition caused when the signal from one circuit causes a disturbance to the signal of thenearby circuit..

CS
Convergence sublayer. One of the two sublayers of the AAL CPCS, 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. See also AAL, CPCS, SAR, and SSCS.

CSA
Canadian Standards Association. Agency within Canada that certifies products that conform to Canadian national safety standards.

CSLIP
Compressed Serial Link Internet Protocol. Extension of SLIP that, when appropriate, allows just header information to be sent across a SLIP connection, reducing overhead and increasing packet throughput on SLIP lines. See also SLIP.

CSMA/CD
Carrier sense multiple access collision detect. Media-access mechanism wherein devices ready to transmit data first check the channel for a carrier. If no carrier is sensed for a specific period of time, a device can transmit. If two devices transmit at once, a collision occurs and is detected by all colliding devices. This collision subsequently delays retransmissions from those devices for some random length of time. CSMA/CD access is used by Ethernet and IEEE 802.3.

CSNET
Computer Science Network. Large internetwork consisting primarily of universities, research institutions, and commercial concerns. CSNET merged with BITNET to form CREN.

CSNP
Complete sequence number PDU. PDU sent by the designated router in an OSPF network to maintain database synchronization.

CSU
Channel service unit. Digital interface device that connects end-user equipment to the local digital telephone loop. Often referred to together with DSU, as CSU/DSU. See also DSU.

CTS
1. Clear To Send. Circuit in the EIA/TIA-232 specification that is activated when DCE is ready to accept data from DTE. 2. Common transport semantic. Cornerstone of the IBM strategy to reduce the number of protocols on networks. CTS provides a single API for developers of network software and enables applications to run over APPN, OSI, or TCP/IP.

CUT
Control Unit Terminal.

Cut-through Packet Switching
Packet switching approach that 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. Also known as on-the-fly packet switching. Contrast with store and forward packet switching.

Daemon
In the UNIX operating system, a computing process that, oncestarted, is not under user control, but continues to run in the background. Daemons usually perform a particular purpose on demand, such as supplying information to another processor. An example in AppleTalk networking is the atalkad daemon, which supplies AppleTalk tunneling information to routers on request.

DAL
Data Access Language. A data base metalanguage designed byApple. A superset of SQL.

DARPA
Defense Advanced Research Projects Agency. US. government agency that funded research for and experimentation with the Internet. Evolved from ARPA, and then, from 1994, back to ARPA.

DARPA Internet
Obsolete term referring to the Internet. See Internet.

DAS
Dual attachment station. Device attached to both the primary and the secondary FDDI rings. Dual attachment provides redundancy for the FDDI ring; if the primary ring fails, the station can wrap the primary ring to the secondary ring, isolating the failure and retaining ring integrity. Also known as a Class A station.

DAT
Digital Audio Tape. A type of storage media used for the backupof computing data.

Data
Information represented in a format readable by a computer.

Data Base
A collection of data that can be selectively retrieved by a type ofapplication knows as a Data Base Management System.

Data Flow Control Layer
Layer 5 of the SNA architectural model. This layer determines and manages interactions between session partners, particularly data flow. Corresponds to the session layer of the OSI model. See also data link control layer, path control layer, physical control llayer, presentation services layer, transaction services layer, and transmission control layer.

Data Link
The physical connection between two devices such as Ethernet,LocalTalk or Token Ring that is capable of carrying information inthe service or networking protocols such as AppleTalk, TCP/IP orXNS.

Data Link Layer
Layer 2 of the OSI reference model. This layer provides reliable transit of data across a physical link. The data link layer is concerned with physical addressing, network topology, line discipline, error notification, ordered delivery of frames, and flow control. The IEEE has divided this layer into two sublayers: The MAC sublayer and the LLC sublayer. Sometimes simply called link layer. Roughly corresponds to the data link control layer of the SNA model. See also application layer, LLC, MAC, network layer, physical layer, presentation layer, session layer, and transport layer.

Data Link Protocol
The protocol that controls the network signaling and receivinghardware, performing data integrity checks and formatting information according to the rules of the data link.

Data Sink
Network equipment that accepts data transmissions.

Data Stream
All data transmitted through a communications line in a single read or write operation.

Datagram
Logical grouping of information sent as a network layer unit over a transmission medium without prior establishment of a virtual circuit. IP datagrams are the primary information units in the Internet. The terms frame, message, packet, and segment are also used to describe logical information grouping at various layers of the OSI reference model and in various technology circles.

dB
Decibels.

DB Connector
Database bus connector. Type of connector used to connect serial and parallel cables to a data bus. DB connector names are of the format DB-x, where x represents the number of (wires) within the connector. Each line is connected to a pin on the connector, but in many cases, not all pins are assigned a function. DB connectors are defined by various EIA/TIA standards.

DCA
Defense Communications Agency. US. government organization responsible for DDN networks such as MILNET. Now called DISA.

DCC
Data Country Code. One of two ATM Address formats developed by the ATM Forum for use by private networks. Adapted from the subnetwork model of addressing in which the ATM layer is responsible for mapping network layer addresses to ATM Addresses. See also ICD.

DCE
Distributed Computing Environment.

DDM
Distributed Data Management. Software in an IBM SNA environment that provides peer-to-peer communication and file sharing. One of three SNA transaction services. See also DIA and SNADS.

DDN
Defense Data Network. US. military network composed of an unclassified network (MILNET) and various secret and top-secret networks. DDN is operated and maintained by DISA. See also DISA and MILNET.

DDP
Datagram Delivery Protocol. Apple Computer network layer protocol that is responsible for the socket-to-socket delivery of datagrams over an AppleTalk internetwork.

DDR
Dial-on-demand routing. Technique whereby a Cisco router can automatically initiate and close a circuit-switched session as transmitting stations demand. The router spoofs keepalives so that end stations treat the session as active. DDR permits routing over ISDN or telephone lines using an external ISDN terminal adapter or modem.

DE
Discard eligible. See tagged traffic.

De Facto Standard
Standard that exists by nature of its widespread use. Compare with de jure standard. See also standard.

De Jure Standard
Standard that exist because of its approval by an official standards body. Compare with de facto standard. See also standard.

Deadlock
1. Unresolved contention for the use of a resource. 2. In APPN, when two elements of a process each wait for action by or a response from the other before they resume the process.

Decay
A loss in the clarity or readability of an electronic signal caused bythe interaction of the signal with its carrier and electrical environment.

Decibel
A measurement that refers to the ratio of the strength of one signalto another. Decibels are commonly used to express signal lossor the relationship of the signal strength to ambient noise.

DECnet
Group of communications products (including a protocol suite) developed and supported by Digital Equipment Corporation. DECnet/OSI (also called DECnet Phase V) is the most recent iteration and supports both OSI protocols and proprietary Digital protocols. Phase IV Prime supports inherent MAC addresses that allow DECnet nodes to coexist with systems running other that have MAC address restrictions. See also DNA.

DECnet Routing
Proprietary routing scheme introduced by Digital Equipment Corporation in DECnet Phase III. In DECnet Phase V, DECnet completed its transition to OSI routing protocols (ES-IS and IS-IS).

Decryption
The reverse application of an encryption algorithm to encrypted data, thereby restoring that data to its original, unencrypted state. See also encryption.

Dedicated LAN
Network segment allocated to a single device. Used in LAN switched network topologies.

Dedicated Line
Communications line that is indefinitely reserved for transmissions, rather than switched as transmission is required. See also leased line.

Default Route
Routing table entry that is used to direct frames for which a next hop is not explicitly listed in the routing table.

Delay
The time between the initiation of a transaction by a sender and the first response received by the sender. Also, the time required to move a packet from source to destination over a given path.

Demand Priority
Media access method used in 100VG-AnyLAN that uses a hub that can handle multiple transmission requests and can process traffic according to priority, making it useful for servicing time-sensitive traffic such as multimedia and video. Demand priority eliminates the overhead of packet collisions, collision recovery, and broadcast traffic typical in Ethernet networks. See also 100VG-AnyLAN.

Demarc
Demarcation point between carrier equipment and CPE.

Demodulation
Process of returning a modulated signal to its original form. Modems perform demodulation by taking an analog signal and returning it to its original (digital) form. See also modulation.

Demultiplexing
The separating of multiple input streams that have been multiplexed into a common physical signal back into multiple output streams. See also multiplexing.

DES
Data Encryption Standard. Standard cryptographic algorithm developed by the US.

Designated Bridge
The bridge that incurs the lowest path cost when forwarding a frame from a segment to the route bridge.

Designated Router
OSPF router that generates LSAs for a multiaccess network and has other special responsibilities in running OSPF. Each multiaccess OSPF network that has at least two attached routers has a designated router that is elected by the OSPF Hello protocol. The designated router enables a reduction in the number of adjacencies required on a multiaccess network, which in turn reduces the amount or routing protocol traffic and the size of the topological database.

Desktop
In the Macintosh user interface, the background image of theFinder on which the icons for applications, directories and datafiles are displayed.

Destination Address
Address of a network device that is receiving data. See also source address.

Deterministic Load Distribution
Technique for distributing traffic between two bridges across a circuit group. Guarantees packet ordering between source-destination pairs and always forwards traffic for a source-destination pair on the same segment in a circuit group for a given circuit-group configuration.

Device Driver
Software that acts as an intermediary between a CPU and aperipheral device. The CPU sends a command to the devicedriver, which translates that command into a command meaningful

DFT
Distributed Function Terminal.

DIN Connector
Deutsche Industrie Norm connector. Multipin connector used in some Macintosh and IBM PC-compatible computers, and on some network processor panels.

DIA
Document Interchange Architecture. Defines the protocols and data formats needed for the transparent interchange of documents in an SNA network. One of three SNA transaction services. See also DDM and SNADS.

Diagnostic
A test or the data from a test which indicates the condition of thestate of a computer or network's health.

Dial-up Line
Communications circuit that is established by a switched-circuit connection using the telephone company network.

Differential Encoding
Digital encoding technique whereby a binary value is denoted by a signal change rather than a particular signal level.

Differential Manchester Encoding
Digital coding scheme where a mid-bit-time transition is used for clocking, and a transition at the beginning of each bit time denotes a zero. The coding scheme used by IEEE802.5 and Token Ring networks.

DIN
Deutsche Industrie Norm. German national standards organization.

Directed Search
Search request sent to a specific node known to contain a resource. A directed search is used to determine the continued existence of the resource and to obtain routing information specific to the node. See also broadcast search.

Directory Services
Services that help network devices locate service providers.

DISA
Defense Information Systems Agency. US. military organization responsible for implementing and operating military information systems, including the DDN. See also DDN.

Discovery Architecture
APPN software that enables a machine configured as an APPN EN to automatically fine primary and backup NNs when the machine is brought onto an APPN network.

Discovery Mode
Method by which an AppleTalk interface acquires information about an attached network from an operational node and then uses this information to configure itself. Also called dynamic configuration.

Distance Vector Routing Algorithm
Class of routing algorithms that iterate on the number of hops in a route to find a shortest-path spanning tree. Distance vector routing algorithms call for each router to send its entire routing table in each update, but only to its neighbors. Distance vector routing algorithms can be prone to routing loops, but are computationally simpler than link state routing algorithms. Also called Bellman-Ford routing algorithm. See also link state routing algorithm and SPF.

Distortion
A change in a electronic signal that occurs when different frequen-cy components of the signal decay at different rates. In a signalmade up of many frequency components (such as a squarewave), the higher frequency components of a signal typicallydecay faster than the lower frequency components.

Distortion Delay
Problem with a communication signal resulting from nonuniform transmission speeds of the components of a signal through a transmission medium. Also called group delay.

DLCI
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). See also LMI.

DLL
Dynamically Linked Libraries. A component of Microsoft's OLE.

DLSw
Data-link switching. Interoperability standard, described in RFC 1434, that provides a method for forwarding SNA and NetBIOS traffic over TCP/IP networks using data link layer switching and encapsulation. DLSw uses SSP (Switch-to-Switch Protocol) instead of SRB, eliminating the major limitations of SRB, including hop-count limits, broadcast and unnecessary traffic, timeouts, lack of flow control, and lack of prioritization schemes. See also SRB, and SSP (Switch-to-Switch Protocol).

DLU
Dependent LU. An LU that depends on the SSCP to provide services for establishing session with other LUs. See also LU and SSCP.

DLUR
Dependent LU Requester. The client half of the Dependent LU Requester/Server enhancement to APPN. The DLUR component resides in APPN ENs and NNs that support adjacent DLUs by securing services from the DLUS. See also APPN, DLU, and DLUS.

DLUR Node
In APPN networks, an EN or NN that implements the DLUR component. See also DLUR.

DLUS
Dependent LU Server. The server half of the Dependent LU Requester/Server enhancement to APPN. The DLUS component provides SSCP services to DLUR nodes over an APPN network. See also APPN, DLU, And DLUR.

DLUS Node
In APPN networks, an NN that implements the DLUS component. See also DLUS.

DMA
Direct memory access. The transfer of data from a peripheral device, such as a hard disk drive, into memory without that data passing through the microprocessor. DMA transfers data into memory at high speeds with no processor overhead.

DMAC
Destination MAC. The MAC address specified in the Destination Address field of a packet. Compare with SMAC. See also MAC address.

DNA
Digital Network Architecture. Network architecture developed by Digital Equipment Corporation. The products that embody DNA (including communications protocols) are collectively referred to as DECnet. See also DECnet.

DNIC
Data Network Identification Code. Part of an X.121 address. DNICs are divided into two parts: the first specifying the country in which the addressed PSN is located and the second specifying the PSN itself. See also X.121.

DNS
Domain Name Service

DNSIX
Department of Defense Intelligence Information System Network Security for Information Exchange. Collection of security requirements for networking defined by the US. Defense Intelligence Agency.

DoD
Department of Defense. US. government organization that is responsible for national defense. The DoD has frequently funded communication protocol development.

domain
1. In the Internet, a portion of the spanning hierarchy tree that refers to general groupings of networks based on organization type or geography. 2. In SNA, an SSCP and the resources it controls. 3. In IS-IS, a logical set of networks.

Domain
Networking system developed by Apollo Computer (now part of Hewlett-Packard) for use in its engineering workstations.

DOS
The operating system of IBM-compatible personal computers.