B channel: Bearer channel
Bearer channel, also known as B channel, is a fullduplex DS0 time slot (64-kbps) that carries analog voice or digital data over ISDN. Compare with D channel, E channel, and H channel.

B2B: Business to Business
Business to Business (B2B) refers to conducting business between two or more companies over the Internet, rather than between businesses and consumers (B2C).

B2BUA: Back-to-Back User Agent
Back-to-Back User Agent (B2BUA) acts as a user agent to both ends of a Session Initiation Protocol (SIP) call. The B2BUA is responsible for handling all SIP signalling between both ends of the call, from call establishment to termination. Each call is tracked from beginning to end, allowing the operators of the B2BUA to offer value-added features to the call. To SIP clients, the B2BUA acts as a User Agent server on one side and as a User Agent client on the other (back-to-back) side. The basic implementation of a B2BUA is defined in RFC 3261.

B2C: Business to Consumer
Business-to-consumer (B2C), also known as business-to-customer, refers to commercial organizations selling products and services to the end consumers over the Internet.

Back End
Back End, in the context of a computer system, refers to a node or software program that provides services to a front end. The front end typically interfaces with users directly while the back end may communicate with other systems such as databases and other systems.

Back Pressure
Back Pressure, in the context of networking, refers to the propagation of network congestion information upstream through an internetwork.

Backbone
Backbone is the part of a network that acts as the primary path for all network traffic, which requires very high bandwidth. A backbone network of a service provider typically connects many enterprise subnetworks and networks of smaller service providers. An enterprise backbone network typically connects many LANs and data centers.

Backchannel
Backchannel refers to the practice of using networked computers to maintain a real-time online conversation while other live spoken sessions are going on. For example, backchannel is popular in conferences and classrooms where audiance and students can use Wi-Fi connections and laptop computers to do online chat during class.

Signaling Backhauling
Signaling Backhauling, also known as signal tunneling, is a scheme where telephony signalling is reliably transported from a gateway to a Media Gateway Controller across a packet-switched network. The gateway need not understand and interpret the signalling information.

Back-Haul
Back-Haul is a communications path which takes traffic farther than the ultimate destination, then routes it back. This is done because the cost of transmission to the more remote location is much lower than a more direct route.

Backhaul
Backhaul or backhauling, also known as signal tunneling, is a scheme where telephony signalling is reliably transported from a gateway to a Media Gateway Controller across a packet-switched network. The gateway need not understand and interpret the signalling information.

Backoff
Backoff means the waiting time period when a host has experienced a collision on a network with MAC protocols before attempting to retransmit. The time for backoff is usually random to minimize the probability that the same nodes will collide again. Increasing the backoff period after each collision also helps to prevent repeated collisions, especially when the network is heavily loaded.

Backplane
Backplane is the physical interface module in many network devices such as a routor or a switch that connects between an interface processor or card and the data buses and the power distribution buses inside a chassis.

Backward-learning
Backward-learning is a routing algorithm used for routing traffic that makes decisions 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 Hybrid
Balanced Hybrid refers to a third type of routing protocol algorithm. (The other two types are distance vector and link-state). The Enhanced Interior Gateway Routing Protocol (EIGRP) is one of the routing protocols using the Balanced Hybrid algorithm.

Balun: balanced-unbalanced
Balun means balanced-unbalanced. Balun is a device designed to convert between balanced and unbalanced electrical signals, such as between coaxial cable and ladder line. Baluns can be considered as simple forms of transmission line transformers.

Bandwidth
Bandwidth refers to the maximum capacity of a network channel. Usually bandwidth is measured in bits per second (bps), kilo-bits per second (Kbps), mega bits per second (Mbps) or gigabits per second (Gbps). For example, Ethernet has a bandwidth of 10-, 100-, 1000 Mbps and 1 and 10 Gbps.

Bandwidth Allocation
Bandwidth Allocation, also known as bandwidth reservation, is the process of assigning bandwidth to users and applications served by a network. Bandwidth Allocation involves assigning priority to different classes 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.

Bandwidth Reservation
Bandwidth Reservation, also known as bandwidth allocation, is the process of assigning bandwidth to users and applications served by a network. Bandwidth reservation involves assigning priority to different classes 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.

Banyan VINES
Banyan Virtual Integrated Network Service (VINES) is a protocol stack defined by Banyan Company, derived from the Xerox Network Systems (XNS) protocols. VINES is based on the UNIX operating system and uses a client/server architecture. The Banyan suite includes the following protocols: VARP (VINES Address Resolution Protocol); VIP (VINES Internet Protocol); ICP (Internet Control Protocol); RTP (Routing Update Protocol); IPC (InterProcess Communications Protocol); SPP (Sequenced Packet Protocol); NetRPC (NetRemote Procedure Call); SteetTalk.
In October 1999 Banyan became ePresence, an internet service provider. At the same time, it announced the obsolescence of VINES and other Banyan products.

BARRNet: Bay Area Regional Research Network
Bay Area Regional Research Network (BARRNet) is a 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.

Baseband
Baseband is a type of a network technology where only one carrier frequency is used. In a baseband network, information is carried in digital form on a single unmultiplexed signal channel on the transmission medium. Ethernet and Token Ring are examples of a baseband network. Baseband in signal transmisson may mean a signal's bandwidth before modulation and multiplexing, or after demultiplexing and demodulation.

Baseline Report
Baseline Report in networking refers to documentations within a certain time period which gives the "normal" operation conditions of a network, a node or a software program. People can use the baseline reports to identify abnormal activities and behavior of the network, a node or a software program when necessary.

BASH: Bourne-Again SHell
Bourne-again shell (BASH) is an interactive UNIX shell based on the traditional Bourne shell, but with increased functionality. Bash is the shell, or command language interpreter, that will appear in the GNU operating system. Bash is an sh-compatible shell that incorporates useful features from the Korn shell (ksh) and C shell (csh). It is intended to conform to the IEEE POSIX P1003.2/ISO 9945.2 Shell and Tools standard. It offers functional improvements over sh for both programming and interactive use. In addition, most sh scripts can be run by Bash without modification.

Bastion Host
A bastion host is a gateway between an inside network and an outside network, which is designed to defend against attacks aimed at the inside network. The system is on the public side of the demilitarized zone (DMZ), unprotected by a firewall or filtering router, and it is fully exposed to attacks. A bastion host must be hardened to anticipate attacks from the public. Typically, a bastion host will be configured with a firewall and provide services like web servers, DNS servers and mail servers.

Baud
Baud, also known as Baud rate, is a 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 is often used in the modem speed.

BBN Planet
BBN Planet is a subsidiary company of BBN(Bolt, Beranek, and Newman) that operates a nationwide Internet access network composed in part by the former regional networks BARRNet, NEARNET, and SURAnet.

BBN Report 1822
BBN Report 1822, a report published by Bolt, Beranek and Newman Inc.(BBN), specified the method or protocol for connecting a host computer to an ARPANET router, called an Interface Message Processor (IMP). This protocol was generally referred to as 1822, the report number. The 1822 specification described the physical layer, the data link layer, and the network layer interface. The host would construct a message containing the numeric address of another host on the network (similar to an IP address on the Internet) and a data field, and transmit the message across the 1822 interface to the IMP.

BBN: Bolt, Beranek, and Newman
BBN refers to the Bolt, Beranek, and Newman, Inc.. It is a high-technology company located in Massachusetts that developed and maintained the ARPANET (and later, the Internet) core gateway system. Its subsidiary, BBN Planet, operates the nationwide Internet access networks.

BBS: Bulletin Board System
Bulletin Board System (BBS), a popular communication system prior WWW between 1980s and 1990s, is a computer system running software that allows users to dial into the system over a phone line or using a terminal program, and to perform such functions as downloading software and data, uploading data, playing games, reading news, and exchanging messages with other users. In current usage the term BBS may be used to refer to any online forum or message board over a Website.

Bc: Committed Burst
Committed Burst (Bc), a term used in Frame Relay systems, is the maximum amount of data (in bits) that a Frame Relay internetwork is committed to accept and transmit onto and over a frame-relay network DLC, over a specific time frame.

B-Channel bundling
B-channel bundling, also known as bearer channel bundling, refers to a technique used to squeeze more voice conversations onto a single line in ISDN. The B channel, one of the fundamental components of the ISDN interface, is circuit-switched and can carry 64,000 bps of voice or data in either direction. B-channel bundling is based on Digital Speed Interpolation (DSI), in which speech is sliced up so that bits are transmitted only when someone is speaking.

BCP: Best Current Practices
Best Current Practices (BCP) are the subseries of IETF RFCs that are written to describe best practices to deploy technologies in the Internet. Rather than specifying a protocol like other RFCs, BCP documents specify the best ways to use the protocols and the best ways to configure options to ensure interoperability between various vendors' products.

BCU: Balanced Configuration Unit
A Balanced Configuration Unit (BCU) is an integrated IBM solution that composed of software and hardware. BCUs are integrated and tested as a pre-configured building block for data warehousing systems. A single BCU contains a balanced amount of disk, processing power and memory to optimize cost-effectiveness and throughput. IT departments can use BCUs to reduce design time, shorten deployments and maintain strong price/performance ratio as they add building blocks to enlarge their BI systems.

Be: Excess Burst
Excess Burst (Be), a term used in the Frame Relay technologies, refers to the number of bits that a Frame Relay internetwork will attempt to transmit after Committed Burst (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
Beacon is the 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.

Bearer Channel
Bearer Channel, also known as B Channel, is a fullduplex DS0 time slot (64-kbps) that carries analog voice or digital data over ISDN. Compare with D channel, E channel, and H channel.

BECN: Backward Explicit Congestion Notification
Backward Explicit Congestion Notification (BECN) is a one bit field in the Frame Relay header that signals to anything receiving the frame (switches and DTEs) that congestion is occurring in the opposite (backward) direction from the frame. Frame Relay switches and DTEs may slow down the data transfer rate in that direction according to the BECN bit.

Bellman-Ford Routing Algorithm
Bellman-Ford Routing Algorithm, also known as Ford-Fulkerson Algorithm, is used as an algorithm by distance vector routing protocols such as RIP, BGP, ISO IDRP, NOVELL IPX. Routers that use this algorithm have to maintain the distance tables (which is a one-dimension array - "a vector"), which tell the distances and shortest path to sending packets to each node in the network. The information in the distance table is always updated by exchanging information with the neighboring nodes. The number of data in the table equals to that of all nodes in networks (excluded itself). The columns of table represent the directly attached neighbors whereas the rows represent all destinations in the network. Each data contains the path for sending packets to each destination in the network and distance/or time to transmit on that path (we call this as "cost"). The measurements in this algorithm are the number of hops, latency, the number of outgoing packets, etc.

BER: Basic Encoding Rules
Basic Encoding Rules (BER), defined in the ITU-T X.209, refer to the rules for data encoding/decoding described in the ASN.1 standard (defined in ITU-T X.208). Basic Encoding Rules may be used to derive the specification of a transfer syntax for values of types defined using the ASN.1 specified in Recommendation X.208. A single ASN.1 object may have several equivalent BER encodes. BER is one of the two encoding methods currently used by CryptoAPI.

BER: Bit Error Rate
Bit Error Rate (BER) is the ratio of received bits that contain errors. BER is usually expressed as ten to a negative power. For example, a transmission might have a BER of 10 to the minus 9, which indicates that, out of a billion bits transmitted, one bit was in error. Typically, the bits in error need to be re-transmitted, which may slow down communications.

Berkeley Sockets
The Berkeley sockets, also known as the BSD socket API, are application programming interfaces (APIs) that comprises a library in C language for developing applications that allows communications between hosts or between processes in one computer, using the concept of a socket. It is able to work with many different I/O devices and drivers, although support for this is dependent on the operating system implementation. This interface implementation is implicit for TCP/IP, and it is therefore one of the fundamental technologies underlying the internet. It was first developed at the University of California at Berkeley for use on UNIX systems. All modern operating systems now have some implementation of the Berkeley socket interface, as it has become the standard interface for connecting to the Internet.

BERT: Bit Error Rate Tester
Bit Error Rate Tester (BERT) is the device that determines the Bit Error Rate (BER) on a given communications channel.

Best-effort Delivery
Best-effort Delivery describes a network system that does not use a sophisticated acknowledgment system to guarantee reliable delivery of information.

BIA: Burned-in MAC Address
Burned-in MAC address (BIA), also known as Burned-In Address, is the last six bytes of a MAC address that are assigned by the manufacturer of a network interface card (NIC). This address sometimes can be overridden by the user, in which the second bit of the most significant byte of the Organisationally Unique Identifier (OUI) is changed to a binary 1. In this case, the NIC is said to be using as a Locally Administered Address (LAA) as its MAC address. If the NIC is not configured to use an LAA as its BIA, then the second bit of the most significant byte of the OUI is changed to a binary 0. In this case, the NIC is said to be using a Universally Administered Address (UAA) as its MAC address.

BICI: Broadband Inter-Carrier Interface
Broadband Inter Carrier Interface (B-ICI), also known as BISDN Inter-Carrier Interface, is based on Broadband ISDN User Part (B-ISUP) signaling messages and parameters. BICI is an interface connecting two different ATM based public network providers or carriers. B-ICI is used to facilitate end-to-end national and international ATM/BISDN services. The B-ICI specification also includes service specific functions above the ATM layer required to transport, operate and manage a variety of intercarrier services across the B-ICI.

BIGA: Bus Interface Gate Array
Bus Interface Gate Array is a Cisco technology that allows its Catalyst swtiches 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
Big-endian is a method of storing or transmitting data in which the most significant bit or byte is presented first, compared with little-endian, which transfers the least important bit/byte first.

Binary
Binary system is the numbering system characterized by ones and zeros (1 = on, 0 = off). Binary system is used in the computer and digital storage and communications.

BIND: Berkeley Internet Name Domain
Berkeley Internet Name Domain (BIND) is an implementation of Domain Name System (DNS) developed and distributed by the University of California at Berkeley. BIND is used to resolve names of systems into IP addresses and vice versa. The BIND DNS Server is available at no charge under the BSD License and it is used on the vast majority of name serving machines on the Internet.

BinHex: Binary Hexadecimal
Binary Hexadecimal(BinHex) is a method for converting binary files into ASCII for transmission by applications, such as e-mail, that can handle only ASCII. BinHex conversion allows you to send word processing, spreadsheet, and application files via email or SFTP. BinHex files were typically given the file extension of .hex or .hqx. The contents of a BinHex file has a message on the first line identifying it as BinHexed, followed by many 64-character lines made up of seemingly random letters, numbers, and punctuation marks. Most applications automatically invoke a decoder such as StuffIt Expander to decode BinHexed files.

BIP: Bit Interleaved Parity
Bit Interleaved Parity (BIP), a term used in ATM, is a method used to monitor errors on a link. A check bit or word is sent in the link overhead for the previous block or frame. Bit errors in the payload then can be detected and reported as maintenance information.

Bit
Bit is the binary digit used in the binary numbering system. A bit is the most basic information unit used in computing and information theory. A single bit is a "one" or a "zero", a "true" or a "false", a "on" or "off", or in general, the quantity of information required to distinguish two mutually exclusive states from each other.

Bit interval
Bit interval is the amount of time, usually in milliseconds or microseconds, a binary one is in the "on" position.

Bit Rate
Bit Rate, usually measured in bits per second (bps), refers to the speed at which bits are transmitted in digital communication and data processing.

BITNET I
BITNET I is the phase I development of the BITNET, a network connecting educational sites separate from the Internet. BITNET I is built on leased lines connecting institutions hierarchically and a store-and-forward protocol called RSCS. See also BITNET.

BITNET II
BITNET II is the phase II development of the BITNET, a network connecting educational sites separate from the Internet. BITNET II enables BITNET traffic to flow over the Internet by encapsulating RSCS files in IP packets. See also BITNET.

BITNET III
BITNET III is the phase III of the development of the BITNET, a network connecting educational sites separate from the Internet. BITNET III provides a global dial-up networking infrastructure that will enable alumni, students, and traveling faculty and staff to connect to their home institution with full IP functionality at low cost from wherever they are through a local telephone call. See also BITNET.

BITNET: Because It's Time NETwork
BITNET, abreviated from "Because It's Time NETwork" or "Because It's There NETwork", is a network connecting educational sites separate from the Internet. Listservs, the most popular form of e-mail discussion groups, originated on BITNET. BITNET is a project of the Corporation for Research and Educational Networking (CREN), a non-profit organization that was dissolved in Jan. 2003. BITNET has shrinked due to the quick emergence of the Internet.

Bit-oriented Protocol
Bit-oriented Protocol is a class of data link layer communication protocols that can transmit frames regardless of frame content. In a bit-oriented transmission, data is transmitted as a steady stream of bits. Compared with byte-oriented protocols, bit-oriented protocols provide full-duplex operation and are more efficient and reliable. IBM's SDLC and HDLC (High-level Data Link Control) are bit-oriented protocols that control synchronous communications.

BitTorrent
BitTorrent, a system developed by the BitTorrent Inc., is a leading P2P network system for downloading large files over the Internet. BitTorrent is a free, open source file-sharing application effective for distributing very large software and media files. The BitTorrent network is designed to support simultaneous upload and download involving many people, sometimes called "swarms." The sites using BitTorrent platform to host P2P file sharing are called Torrents.

Black Hole
Black Hole, in the networking world, refers to 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 Multiplexer Channel
Block-multiplexer channel, also referred to as OEMI channel and 370 block mux channel, is an IBM designed channel that implements the FIPS-60 channel, a U.S. channel standard. Block-multiplexer channel has a number of subchannels, each associated with an I/O device or a group of I/O devices. The subchannel is the logical entity that controls an I/O operation and contains the addresses, count, and control bits associated with the operation. The channel provides the data paths and controls for communicating with the CPU, main storage, and I/O control units and for associating the proper subchannel with each communications sequence. The block-multiplexer channel, being designed for high data rates, is limited to interleaving complete blocks of data.

Blocking State
Blocking State refers to a Spanning Tree Protocol port state in which the bridge or switch does not process any frames (input or output) on the interface, with the exception of STP messages.

BLSR: Bidirectional Line Switch Ring
Bidirectional Line Switch Ring (BLSR) is a SONET ring architecture that provides working and protection fibers between nodes. If the working fiber between nodes is cut, traffic is routed automatically onto the protection fiber.

BNI: Broadband Network Interface
Broadband Network Interface (BNI) is the network interface that connects broadband CPE and a switch or a router. The broadband access technologies may include DSL, ATM, Ethernet and T1/E1, T3/E3 and more.

BNM: Broadband Network Module
Broadband Network Module (BNM) is the lines card available in a range of interfaces, including 10/100 Ethernet, Gigabit Ethernet, T1/E1, DS-3/E3, Circuit Emulation (CEM), Frame Relay, and Asynchronous Transfer Mode (ATM).

BNN: Boundary Network Node
Boundary Network Node (BNN), an IBM SNA terminology, refers to a subarea node that provides boundary function support for adjacent peripheral nodes. This support includes sequencing, pacing, and address translation. Boundary Network Node is also known as Border Node.

BONDING: Bandwidth ON Demand Interoperability Group
Bandwidth ON Demand Interoperability Group(BONDING) is a consortium of data communications equipment vendors and service providers who joined together to create a standardized inverse multiplexing protocol so that inverse multiplexers from different vendors could interoperate. The specification by BONDING is referred to as the "BONDING specification."

Boolean
Boolean, named after George Boole (an English mathematician in the mid 19th century) is a complete mathematical logic system. Boolean logic and algebra has many applications in electronics, computer hardware and software.

Boolean Algebra
Boolean algebra is an algebraic structure (a collection of elements and operations on them obeying defining axioms) that captures essential properties of both set operations and logic operations. Specifically, it deals with the set operations of intersection, union, complement; and the logic operations of AND, OR, NOT. A Boolean algebra is also called a Boolean lattice.

Boolean AND
Boolean AND is one of the operations in the Boolean algebra that is performed on a pair of one-digit binary numbers. The result is another one-digit binary number. For example, 1 AND 1 yields 1; all other combinations yield 0.

Boolean logic
Boolean logic is a complete system for logical operations. It was named after George Boole, an English mathematician in the mid 19th century. Boolean logic has many applications in electronics, computer hardware and software. For example, in circuit design in electrical engineering, 0 and 1 may represent the two different states of one bit in a digital circuit, typically high and low voltage. Circuits are described by expressions containing variables, and two such expressions are equal for all values of the variables if, and only if, the corresponding circuits have the same input-output behavior. Furthermore, every possible input-output behavior can be modeled by a suitable Boolean expression. Basic logic gates such as AND, OR, and NOT gates may be used alone, or in conjunction with NAND, NOR, and XOR gates, to control digital electronics and circuitry. Whether these gates are wired in series or parallel controls the precedence of the operations.

Boolean OR
Boolean OR is one of the operations in the Boolean algebra that is performed on a pair of one-digit binary numbers. The result is another one-digit binary number. For example, 0 OR 0 yields 0; All other combinations yield 1.

Boolean value
Boolean value, also known as boolean datatype, is a primitive datatype having two values: one and zero (sometimes called true and false). It is the special case of a binary numeric datatype of only one digit, or bit, and can also be represented in any other radix by restricting the range of allowed values for certain operations. This datatype is used in boolean and other operations such as and (AND, &, *), or (OR, |, +), exclusive or/not equivalent (xor, NEQV, ^), equal (EQV, =, ==) and not (NOT, ~, !) which correspond to some of the operations of Boolean algebra and arithmetic.

Boot Helper
Boot Helper is the minimum-function of a system image that serves only to boot the full-function for the system image.

Border Gateway
Border Gateway is the router located at the border between autonomous domains that communicates with routers in other autonomous systems. Border Gateway Protocol (BGP) is often used as the language for such communications.

Border Node
Border node, also known as Boundary Network Node (BNN) is a logical node in the IBM SNA that is in a specific peer group, and has at least one link that crosses the peer group boundary. Border node has functions including sequencing, pacing, and address translation. The current border node is called Extended Border Node capable of multiple APPN network connections and can maintain CP-CP connectivity with a network node that has a different NETID.

Bottleneck
A bottleneck point in network communication is a point in a network at which information is processed more slowly. Such network point maybe a node (a switch, router or server), or any element (a hard drive, I/O card or network interface card NIC) that slows network communication rates.

BPDU: Bridge Protocol Data Unit
Bridge Protocol Data Unit (BPDU), a protocol in the PPP suite, refers to some of "hello packets" of the spanning tree protocol sent out at intervals to exchange information among bridges in the network. BPDUs help describe and identify attributes of a switch port and allow for switches to obtain information about each other.

BPI: Baseline Privacy Interface
Baseline Privacy Interface (BPI), as defined in the Data Over Cable Service Interface Specifications (DOCSIS), provides a data encryption scheme that protects data sent between cable modems and Cable Modem Termination System (CMTS) in a data over cable network. BPI can also be use to authenticate cable modems and authorize the transmission of multicast traffic. The secondary goal of BPI is to provide basic protection from theft of service for cable operators.

BPS: Bits Per Second
Bits Per Second (bps) is a commonly-used measure of the rate of data transmission, which specifies the number of bits that are transmitted in one second. BPS may be prefixed with multipliers such as K (kbps), M (mbps), and G (gbps) which refers to kilo (thousand), mega (million) and giga (billion) of bits per second.

BRA: Basic Rate Access
Basic Rate Access (BRA) is one of the two ISDN services. The other one is Primary Rate Access (PRA). Basic Rate Access (BRA) provides an ISDN user with simultaneous access to two 64 kbps data channels using the existing twisted pair copper telephone cable. Each data channel is referred to as a B-channel and can carry voice or data. Another channel, the D-channel, operates at 16 kbps and is used for signalling to the ISDN. The total data rate of BRA is therefore 144 kbps. The two B-channels and the single signalling channel give rise to the term '2B+D'. Basic rate ISDN is intended for low capacity usage, such as that required for homes and small businesses.

BRF: Bridge Relay Function
Bridge Relay Function (BRF) is an internal bridge function on a Token Ring switch that is responsible for forwarding frames between port groupings with the same logical ring number. Within a BRF, source route bridging or source route transparent bridging can be used to forward frames.

BRHR: Basic Research and Human Resources
Basic Research and Human Resources (BRHR), a component of the High Performance Computing and Communications (HPCC) program, is designed to increase the flow of innovative ideas by encouraging investigator-initiated, long-term research in scalable high-performance computing; to increase the pool of skilled and trained personnel by enhancing education and training in high performance computing and communications; and to provide the infrastructure needed to support these research and education activities.

BRI: Basic Rate Interface
Basic Rate Interface (BRI) is an ITU-T ISDN multipurpose user interface standard for simultaneous voice and data services provided over two 64-kb/s bearer channels and one 16-kb/s data channel (2B+D) access arrangement to each user location. The B channels are used for voice or user data, and the D channel is used for any combination of: data, control/signalling and X.25 packet networking. The two B channels can be bonded together giving a total data rate of 128 kbit/s. BRI is the kind of ISDN interface most likely to be found in residential service.

Bridge Forwarding
Bridge Forwarding, as described in the IEEE 802.1 standard, is the 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.

Bridge Group
Bridge Group is a feature in the Virtual Local Area Network (VLAN) that assigns network interfaces to a particular spanning-tree group. Bridge groups can be compatible with the IEEE 802.1 or the DEC specification. Bridge groups enable network managers to group users logically rather than by physical location. It can also be considered a broadcast domain set up within a switch. A group of devices that belong to the same VLAN, but are part of different LAN segments, are configured to communicate as if they were part of the same LAN segment.

Bridge ID
Bridge ID, an 8-byte value, is defined for use by Spanning Tree Protocol, that represents a bridge or switch. The first 2 bytes consist of a priority value, and the last 6 bytes typically consist of a MAC address on the bridge or switch.

Bridge MIB
Bridge MIB (Management Information Base) is a specification for use with network managing protocols in TCP/IP based internets. In particular, it defines objects for managing bridges based on the IEEE 802.1d draft standard between LAN segments. Managed objects are accessed via the Management Information Base or MIB. Objects in the MIB are defined using the subset of Abstract Syntax Notation One (ASN.1) defined in the SMI. In particular, each object is named by an OBJECT IDENTIFIER, an administratively assigned name, which specifies an object type. The object type together with an object instance serves to uniquely identify a specific instantiation of the object.

Bridge Number
Bridge Number refers to the number that identifies each bridge in a source-route bridging (SRB) LAN, which was developed by IBM and was proposed to the IEEE 802.5 committee as the means to bridge between all LANs. Parallel bridges must have different bridge numbers.

Bridge Static Filtering
Bridge Static Filtering, as defined in the IEEE802.1 standard, is a 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.

Bridging
Bridging is the process of passing packets to another network segment without regard to the network operating system. Packets, forwarded using bridging, are passed at the data link layer (layer 2) of the OSI model. In an environment where diverse network operating systems exist, such as between Appletalk, Ethernet and NetWare, a bridge can move data between the networks at layer 2 (routing can deliver packets to discreet addresses in the network). Bridge, the network device using bridging process, is a layer-2 device that can bridge different network segments. The bridge keeps a table of all segments and forward frames properly to make sure that communications within or across segments are conducted smoothly.

Broadband
Broadband in networking and telecommunication refers to any type of transmission technique that carries several data channels over a common wire. In home networking, "broadband" usually refers to high-speed Internet access using broadband transmission technique. The mostly used broadband access technologies include DSL (over normal telephone lines), DOCSIS (over cable wires) etc. So-called broadband routers and broadband modems are network devices that support both DSL and DOCSIS.

Broadband Medic
Broadband Medic is a piece of software issued by the internet service provider NTL in the United Kingdom. Used to diagnose network and email issues.

Broadband Network
Broadband Network is a network capable of transporting multiple services including voice, interactive full-motion video, and data simultanously on the same physical cable over long distances. In contrast, a narrowband network can transport only traditional telephone service, electronic mail, paging services, and faxes.

Broadband Router
Broadband router is an access router used by Small Office Home Office (SOHO) or residential customers to access the Internet via DSL or cable moderns. A broadband router typically combines the features of a traditional network switch, a firewall, and a DHCP server. A broadband router supports file sharing, Internet connection sharing, and home LAN.

Broadcast
Broadcast on a network means one node transmiting packets to all other nodes in the same domain simultaneously. Multicast is a special form of broadcast, in which a selected group of users who requested to listen to the broadcast, will receive the broadcasts. Broadcast transmission is supported on most LANs (e.g. Ethernet). Broadcast can also happen in a virtual LAN (VLAN). IPv6 has unicast, multicast, and anycast. Broadcast has disappeared as a term, but is considered one form of multicast.

Broadcast Address
Broadcast Address is a special address for all devices to open and process the message if a packet is addressed to this address. For example, the MAC address with all 1s (1xFFFFFFFF) is a broadcast address, and the IP address 255.255.255.255 is the general broadcast address. Any device sees a message addressed to the broadcast address shall open it and then pass the message to the next station. In a subnet, the broadcast address is the highest numerical value in the range of numbers for the subnet. The broadcast address cannot be assigned as an IP address to a computer.

Broadcast Domain
Broadcast Domain is a restricted area in which information is shared by all devices. In other words, all the devices attached to the network that receive the broadcast are part of the same broadcast domain. In a shared Ethernet, stations broadcast frames to all other nodes through a shared medium. Other nodes listen to the broadcasts but only receive the frames addressed to them. Therefore, all nodes in a shared Ethernet belong to the same broadcast domain. Virtual LAN technology can create a virtual broadcast domain.

Broadcast Search
Broadcast Search refers to the propagation of a search request to all network nodes if the location of a resource is unknown to the requester, while the directed search is a request that is sent along a predefined path from one network node to another network node. A broadcast search is issued because a directed search using database information has failed or there is no database information for the requested resource.

Broadcast Storm
A broadcast storm is a networking situation in which messages are broadcast on a network, and each message prompts a receiving node to respond by broadcasting its own messages on the network that in turn prompt further responses, and so on. A broadcast storm may cause congestion of the network as the number of packets on the network increases. Broadcast storms can usually be prevented by carefully configuring a network to block illegal broadcast messages.

Broadcast Subnet
Broadcast Subnet refers to one of the special subnet with subnet bits numbers all with a binary value 1. When subnetting a Class A, B, or C network, two subnet numbers are discouraged from use; one of these two subnets is the broadcast subnet.

Brouter
Brouter is nickname of a device that functions as both a router and a bridge. A brouter routes specific types of packets, such as TCP/IP packets to specific desitination. Any other packets it receives are simply forwarded to other network(s) connected to the device (this is the bridge function).

Browser
Browser is a web graphic user inerface (GUI) based on hypertext client application. Browser is used to access hypertext documents and other services located on innumerable remote servers throughout the WWW and Internet. The most popular browsers include Internet Explorer, Mosaic, Firefox, and Netscape Navigator.

BSD: Berkeley Standard Distribution
Berkeley Standard Distribution (BSD), also known as Berkeley Software Distribution or Berkeley Unix, is the Unix operating system distributed by the University of California, Berkeley starting in the 1970s. BSD is also a term used to describe any of a variety of UNIX-type operating systems based on the UC Berkeley BSD operating system.

BSTUN: Block Serial Tunnel
Block Serial Tunnel (BSTUN), a feature in Cisco routers, enables Cisco 2500, 3600, 4000, 4500, 4700 and 7200 series routers to support devices that use the Binary Synchronous Communications (Bisync) datalink protocol and asynchronous security protocols that include Adplex, ADT Security Systems, Diebold, asynchronous generic, and mdi traffic. The support of the Bisync protocol enables enterprises to transport Bisync traffic and SNA multiprotocol traffic over the same network.

BT: Burst Tolerance
Burst Tolerance(BT) is a parameter defined by the ATM Forum for ATM traffic management. For Variable bit-rate (VBR) connections, BT determines the size of the maximum burst of contiguous cells that can be transmitted. Burst tolerance is not applicable to the shaping of best-effort connections and the PCR-only mode of shaping for VBR connections.

BTA: Basic Trading Area
Basic Trading Area (BTA) refers to the area or "footprint" in which an entity is licensed to transmit their frequencies. BTAs were established by Rand McNally and are defined as county lines. Rand McNally licensed their mapping data to the FCC for ease of designation for site licenses.

BTU: British Thermal Units
The British Thermal Unit (BTU) is a unit of energy used in the United States. It is also still occasionally encountered in the UK, in the context of older heating and cooling systems. In most other areas, it has been replaced by the SI unit of energy, the joule (J). A Btu is defined as the amount of heat required to raise the temperature of one pound avoirdupois of water by one degree Fahrenheit. 143 Btu is required to melt a pound of ice. As is the case with the calorie, several different definitions of the Btu exist, which are based on different water temperatures and therefore vary by about 0.5%.

Burned-in Address
The Burned-In Address (BIA), also known as burned-in MAC address, is the last six bytes of a MAC address that are assigned by the manufacturer of a network interface card (NIC). This address sometimes can be overridden by the user, in which case the second bit of the most significant byte of the Organisationally Unique Identifier (OUI) is changed to a binary 1. In this case, the NIC is said to be using as a Locally Administered Address (LAA) as its MAC address. If the NIC is not configured to use an LAA as its BIA then the second bit of the most significant byte of the OUI is changed to a binary 0. In this case, the NIC is said to be using a Universally Administered Address (UAA) as its MAC address.

Burst
In data communications, a burst refers to a continuous transfer of data without interruption from one device to another. For example, IP traffic headed in the same general direction is assembled and routed as a burst through the network. The burst is carried on two wavelengths, one for data and another for header information that guides the burst through the network.

Burst transmission
Burst transmission refers to the data transmission that combines a very high data signaling rate with very short transmission time. It may also means the operation of a data network in which data transmission is interrupted at intervals.

Burstable Billing
Burstable Billing is a type of billing agreement which allows subscriber to use more than they agreed bandwidth without the financial penalty of purchasing a higher Committed Information Rate (CIR) from an internet service provider (ISP). Usage charges are generally based upon the 95th percentile which effectively filters the peaks from your usage profile. Under this agreement, you could burst to full capacity continuously for up to 65 min per day with no financial penalty.

Bursty Traffic
Bursty traffic refers to an uneven pattern of data transmission: sometime very high data transmission rate while other time it might be very low.

Bus and Tag Channel
Bus and Tag Channel is a common name for the parallel channel between IBM mainframes and peripherals. One set of cables carries the data (the bus), and another set is for control information (the tag). It incorporated copper multiwire technology and replaced by the ESCON channel.

Bus Contention
Bus contention is an undesirable state of the bus of a computer, in which more than one memory mapped device or the CPU is attempting to place output values onto the bus at once. Normally, integrated circuits that connect to the bus are designed so that the likelihood of bus contention is nil provided that the chips are operated within their rated set-up times and so forth. However, if the bus is deliberately driven too fast, these setup times may be violated -- leading to contention. Contention may also arise on a system whose memory mapping is programmable, and illegal values are written to the registers controlling the mapping.

Bus Network
Bus network refers to a network architecture in which a set of clients are connected via a shared communications line, called a bus. There are several common instances of the bus architecture, including one in the motherboard of most computers, and those in some versions of Ethernet networks.

Bus Topology
Bus Topology is a LAN architecture in which all nodes are connected by one linear bus (cable) and transmissions from network stations propagate the length of the cable medium and are received by all other nodes.

BVI: Bridge Group Virtual Interface
Bridge Group Virtual Interface(BVI) is the logical Layer 3-only interface associated with a bridge group when Integrated routing and bridging (IRB) is configured. Integrated routing and bridging uses a Bridge-Group Virtual Interface (BVI) to enable these interfaces to exchange packets for a given protocol. A BVI is a virtual interface within the campus switch router that acts like a normally routed interface. A BVI does not support bridging, but it actually represents the corresponding bridge group to routed interfaces within the switch router. The interface number is the link between the BVI and the bridge group.

BX.25: Bellcore X.25
Bellcore X.25(BX.25) is a variation of X.25 implemented by AT&T and some Regional Bell Operation Companies (RBOCs).

Bypass Mode
Generally speaking, Bypass Mode refers to an operation mode in a system that is bypassed by design. In the FDDI and Token Ring networks, Bypass mode refers to that an interface has been removed from the ring.

Bypass Relay
Bypass Relay is a device that allows a particular Token Ring interface to be shut down and thus effectively removed from the ring.

Byte
Byte is a basic unit of computer storage with 8 bits. It is the smallest addressable unit in a computer's architecture. It usually holds one character of information for western languages. For some oriental languages such as Chinese, two bytes (16bits) are required for one character.

Byte Multiplexer Channel
Byte Multiplexer Channel is one of the two channel types in the IBM System/360 architecture. A selector channel is capable of operating with relatively high data rates but with only one device at a time, and a byte-multiplexer channel capable of simultaneously operating many devices but at relatively low data rates.

Byte Reversal
Byte Reversal is the process of changing the order of the bytes in data you input to the block. It is used for integers and addresses on devices with Intel microprocessors. You may use this when your process communicates between targets that use different endianness, such as between Intel processors that are little-endian and others that are big-endian. When you transmit data to a processor with different endianness, place a byte reversal block just before the send block in a model and immediately after the receive block to ensure that transmitted data has the correct endianness.

Byte-oriented Protocol
Byte-oriented Protocol is a class of data-link communications protocols that use a specific character from the user character set to delimit frames. These protocols largely have been replaced by bit-oriented protocols.