Section 3 B Terms Flashcards
B8ZS
Binary 8-zero substitution. Line-code type, used on T1 and E1 circuits, in which a special code is substituted whenever 8 consecutive zeros are sent through the link. This code is then interpreted at the remote end of the connection. This technique guarantees ones density independent of the data stream. Sometimes called bipolar 8-zero substitution. Compare with AMI. See also ones density.
Back End
Node or software program that provides services to a front end. See also client, front end, and server.
Back End Processor
A computer running an application that supplies data to other computers on demand, but has no user interface.
Back Pressure
Propagation of network congestion information upstream through an internetwork.
Backbone
Referring to the internet, a central network that provides a pathway for other networks to communicate.
Background Task
A computing task that is executing while another task or application is displaying its user interface.
Backoff
The (usually random) retransmission delay enforced by contentious MAC protocols after a network node with data to transmit determines that the physical medium is already in use.
Backplane
The communication channels of a single device’s architecture, such as in a hub or concentrator.
Backup
A copy of a set of files made for replacement purposes in case the original set is damaged or lost.
Backward Compatible
An upgraded component of a computing system that can be used interchangeably with its previous version.
Backward Learning
Algorithmic process used for routing traffic that surmises information by assuming symmetrical network conditions. For example, if node A receives a packet from node B through intermediate node C, the backward-learning routing algorithm will assume that A can optimally reach B through C.
Balanced Configuration
In HDLC, a point-to-point network configuration with two combined stations.
Balun
Balanced/Unbalanced. A device that links together dissimilar wire types and attempts to minimize any negative effects to the signal that would normally result from the dissimilarity.
Band
In analog communications, the range of frequencies over which a communication system operates.
Bandwidth
In analog communications, the difference between the highest and lowest frequencies available in the band. In digital communications, bandwidth is loosely used to refer to the information-carrying capacity of a network or component of a network.
Bandwidth Reservation
Process of assigning bandwidth to users and applications served by a network. Involves assigning priority to different flows of traffic based on how critical and delay-sensitive they are. This makes the best use of available bandwidth, and if the network becomes congested, lower-priority traffic can be dropped. Sometimes called bandwidth allocation. See also call priority.
BARRNet
Bay Area Regional Research Network. Regional network serving the San Francisco Bay Area. The BARRNet backbone is composed of four University of California campuses (Berkeley, Davis, Santa Cruz, and San Francisco), Stanford University, Lawrence Livermore National Laboratory, and NASA Ames Research Center. BARRNET is now part of BBN Planet.
Base address
The lowest address available in an address range.
Baseband
A communication system in which only one signal is carried at any one time.
Baud
Unit of signaling speed equal to the number of discrete signal elements transmitted per second. Baud is synonymous with bits per second (bps), if each signal element represents exactly 1 bit.
Baud Rate
The number of voltage or frequency transitions per second.
BBN
Bolt, Beranek, and Newman, Inc. High-technology company located in Massachusetts that developed and maintained the ARPANET and later, the Internet, core gateway system.
BBN Planet
Subsidiary company of BBN that operates a nationwide Internet access network composed in part of the former regional networks BARRNET, NEARNET, and SURAnet.
Bc
Committed Burst. Negotiated tariff metric in Frame Relay internetworks. The maximum amount of data (in bits) that a Frame Relay internetwork is committed to accept and transmit at the CIR.
B Channel
Bearer channel. In ISDN, a full-duplex, 64-kbps channel used to send user data. Compare to D channel, E channel, and H channel.
Be
Excess Burst. Negotiated tariff metric in Frame Relay internetworks. The number of bits that a Frame Relay internetwork will attempt to transmit after Bc is accommodated. Be data is, in general, delivered with a lower probability than Bc data because Be data can be marked as DE by the network.
Beacon
Frame from a Token Ring or FDDI device indicating a serious problem with the ring, such as a broken cable. A beacon frame contains the address of the station assumed to be down.
BECN
Backward explicit congestion notification. Bit set by a Frame Relay network in frames traveling in the opposite direction of frames encountering a congested path. DTE receiving frames with the BECN bit set can request that higher-level protocols take flow control action as appropriate. Compare with FECN.
Bellcore
Bell Communications Research. Organization that performs research and development on behalf of the RBOCs.
Benchmark
A test performed t compare a computer process in one set of circumstances to another.
BER
- Bit error rate. The ratio of received bits that contain errors. 2. Basic encoding rules. Rules for encoding data units described in the ISO ASN.1 standard.
BGP
Border Gateway Protocol. Interdomain routing protocol that replaces EGP. BGP exchanges reachability information with other BGP systems. It is defined by RFC 1163.
BGP4
BGP Version 4. Version 4 of the predominant interdomain routing protocol used on the Internet. BGP4 supports CIDR and uses route aggregation mechanisms to reduce the size of routing tables.
BIGA
Bus Interface Gate Array. Technology that allows the Catalyst 5000 to receive and transmit frames from its packet-switching memory to its MAC local buffer memory without the intervention of the host processor.
Big-endian
Method of storing or transmitting data in which the most significant bit or byte is presented first. Compare with little-endian.
Binary
- A numerical system using “2” as its base. 2. Data that is encoded or presented in machine-readable form (1’s & 0’s).
BIND
Berkeley Internet Name Domain. The standard TCP/IP naming service that links network names with IP addresses.
Biphase Coding
Bipolar coding scheme originally developed for use in Ethernet. Clocking information is embedded into and recovered from the synchronous data stream without the need for separate clocking leads. The biphase signal contains no direct current energy.
Bipolar
Electrical characteristic denoting a circuit with both negative and positive polarity. Contrast with unipolar.
BISDN
Broadband ISDN. ITU-T communication standards designed to handle high-bandwidth applications such as video. BISDN currently uses ATM technology over SONET-based transmission circuits to provide data rates from 155 to 622 Mbps and beyond.
Bit
The basic unit of data representation in digital computers. a memory location that can have one of two values.
BITNET
“Because It’s Time” Networking Services. Low-cost, low-speed academic network consisting primarily of IBM mainframes and 9600-bps leased lines. BITNET is now a part of CREN. See also CREN.
BITNET III
Dial-up service providing connectivity for members of CREN.
Bit-oriented Protocol
Class of data link layer communication protocols that can transmit frames regardless of frame content. Compared with byte-oriented protocols, bit-oriented protocols provide full-duplex operation and are more efficient and reliable. Compare with byte-oriented protocol.
Bit pattern
A sequence of bits that has a specific purpose or meaning.
Bit rate
The rate at which bits are transmitted or received during communication, expressed as the number bits in a given amount of time, usually one second.
Bitmap
A data structure that uses bits to represent the attributes of an object that is not character-based.
Black Box
A device that performs a function using mechanisms that are unimportant or impossible to understand.
Black Hole
Routing term for an area of the internetwork where packets enter, but do not emerge, due to adverse conditions or poor system configuration within a portion of the network.
Block
The basic unit of storage on a computer disk.
Blocking
In a switching system, a condition in which no paths are available to complete a circuit. The term is also used to describe a situation in which one activity cannot begin until another has been completed.
Block Multiplexer I Channel
M-style channel that implements the FIPS-60 channel, AUS. Channel standard. This channel is also referred to as OEMI channel and 370 block mux channel.
BNC
Bayonet “N” Connector. 1. The locking connector type used in 10Base2 (Thin Ethernet). 2. Any connector similar to the type used by 10Base2 for CATV, and other electronic uses.
BNN
Boundary network node. In SNA terminology, a subarea node that provides boundary function support for adjacent peripheral nodes. This support includes sequencing, pacing, and address translation.
Board
A printed circuit and the substrate on which it lies.
BOC
Bell operating company. See RBOC.
Boot
A computer’s startup operation.
Boot Drive
The disk that contains a computers’ startup instructions.
BOOTP
Bootstrap Protocol. An IP protocol used by diskless workstations to receive boot information from a boot server.
Boot PROM
Boot programmable read-only memory. Chip mounted on a printed circuit board used to provide executable boot instruction to a computer device.
Border Gateway
Router that communicates with routers in other autonomous systems.
Boundary Function
Capability of SNA subarea nodes to provide protocol support for attached peripheral nodes. Typically found in IBM 3745 devices.
BPDU
Bridge protocol data unit. Spanning-Tree Protocol hello packet that is sent out at configurable intervals to exchange information among bridges in the network.
BPS
Bits Per Second. A commonly-used measure of the rate of data transmission that specifies the number of bits that are transmitted in one second. May be prefixed with multipliers such as K, M, and G which indicate rates of thousands, millions and billions of bits per second.
BRI
Basic Rate Interface. an ISDN service with two bearer channels at 64 KBPS plus a “Data-Link” or control channel at 16 KBPS.
Bridge
A Data Link Layer device that limits traffic between two network segments by filtering the data between them based on hardware addresses.
Bridge Forwarding
Process that uses entries in a filtering database to determine whether frames with a given MAC destination address can be forwarded to a given port or ports. Described in the IEEE 802.1 standard. See also IEEE 802.1.
Bridge Number
Number that identifies each bridge in an SRB LAN. Parallel bridges must have different bridge numbers.
Bridge Static Filtering
Process in which a bridge maintains a filtering database consisting of static entries. Each static entry equates a MAC destination address with a port that can receive frames with this MAC destination address and a set of ports on which the frames can be transmitted. Defined in the IEEE802.1 standard.
Broadband
A transmission system capable of carrying many channels of communication simultaneously by modulating them on one of several carrier frequencies.
Broadcast
An information transmission that is intended to be interpreted by all entities capable of receiving it.
Broadcast Address
Special address reserved for sending a message to all stations. Generally, a broadcast address is a MAC destination address of all ones. Compare with multicast address and unicast address.
Broadcast Domain
The set of all devices that will receive broadcast frames originating from any device within the set. Broadcast domains are typically bounded by routers because routers do not forward broadcast frames.
Broadcast Search
Propagation of a search request to all network nodes if the location of a resource is unknown to the requester.
Broadcast Storm
Undesirable network event in which many broadcasts are sent simultaneously across all network segments. A broadcast storm uses substantial network bandwidth and, typically, causes network time-outs.
Brouter
A device that incorporates the functionality of a bridge and a router in a single unit.
BSC
Binary synchronous communication. Character-oriented data link layer protocol for half-duplex applications. Often referred to simply as bisync.
BSD
Berkeley Software Distribution. UC Berkeley’s distribution of the Unix operating system.
BT
Burst tolerance. Parameter defined by the ATM Forum for ATM traffic management. For VBR connections, BT determines the size of the maximum burst of contiguous cells that can be transmitted.
Buffer
A temporary memory storage area for information.
Bug
A flaw in a software program.
Bundled
Refers to the practice of automatically including an additional application or capability in the sale or delivery of a computing component that is not ordinarily associated with that component.
BUS
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.
Bus
A type of network topology in which nodes are connected alonga continuous path that is not a closed circuit. Also refers to acommunications channel used by a single computer such asNubus, SCSI, etc.
Bus and Tag Channel
IBM channel, developed in the 1960s, incorporating copper multiwire technology. Replaced by the EXCON channel. See also ESCON channel and parallel channel.
Bus Topology
Linear LAN architecture in which transmissions from network stations propagate the length of the medium and are received by all other stations. Compare with ring topology, star topology, and tree topology.
Bypass Mode
Operating mode on FDDI and Token Ring networks in which an interface has been removed from the ring.
Bypass Relay
Allows a particular Token Ring interface to be shut down and thus effectively removed from the ring.
Byte
A group of 8 bits.
Byte-oriented Protocol
Class of data-link communications protocols that use a specific character from the user character set to delimit frames. These protocols have largely been replaced by bit-oriented protocols. Compare with bit-oriented protocol.
Byte Reversal
Process of storing numeric data with the least-significant byte first. Used for integers and addresses on devices with Intel microprocessors.
