B

B (bearer) channel

In ISDN, the channel that carries the data.

See also [D channel]

backbone

A network segment that acts as a trunk between other network segments. Backbones are typically high-bandwidth implementations such as fiber-optic cable.

backup schedule

A document or another plan that defines the point at which backups are made, what backups are made, and what data is backed up.

bandwidth

The rated throughput capacity of a given network protocol or medium.

baseband

A term applied to any media that is capable of carrying only a single data signal at a time. Compare with broadband.

baseline

A measurement of performance of a device or system for the purposes of future comparison. Baselining is a common server administration task.

baud rate

The speed or rate of signal transfer. The word baud is derived from the name of French telegraphy expert J. M. Baudot.

BDC (backup domain controller)

A Windows NT server that provides a backup of the PDC's user, group, and security information.

See also [primary domain controller]

binary

A base 2 numbering system that is used in digital signaling. It uses only the numbers 1 and 0.

Bindery

The name of the user account information database on NetWare servers up to and including NetWare 3.x

binding

The process of associating a protocol and an NIC.

biometrics

The science and technology of measuring and analyzing biological data. Biometrics is increasingly being used for security purposes, to analyze and compare characteristics such as voice patterns, retina patterns, and hand measurements.

BIOS (Basic Input/Output System)

A basic set of instructions that a device needs to operate.

bit

An electronic digit used in the binary numbering system. Bit is a contraction of the terms binary and digit.

blackout

A total loss of electrical power.

Blue Screen of Death

The term for the blue-screen STOP errors that occur and halt the system in Windows NT and Windows 2000.

BNC (British Naval Connector)

A T-shaped connector that is used to connect a device to a thin coaxial Ethernet network.

bound media

A term used to describe any media that have physical constraints, such as coaxial, fiber-optic, and twisted pair. Compare with unbound media.

boundless media

See [unbound media]

BRI (Basic Rate Interface)

An ISDN digital communications line that consists of three independent channels: two B channels, each at 64Kbps, and one D channel, at 16Kbps. ISDN BRI is often referred to as 2B+D.

See also [Integrated Services Digital Network]

See also [Primary Rate Interface]

bridge

A device that connects and passes packets between two network segments that use the same communications protocol. Bridges operate at the data-link layer of the OSI model. A bridge filters, forwards, or floods an incoming frame based on the MAC address of that frame.

bridging address table

A list of MAC addresses that a bridge keeps and uses when it receives packets. The bridge uses the bridging address table to determine which segment the destination address is on before it sends the packet to the next interface or drops the packet (if it is on the same segment as the sending node).

broadband

A communications strategy that uses analog signaling over multiple communications channels.

broadcast

A packet delivery system in which a copy of a packet is given to all hosts attached to the network.

broadcast storm

An undesirable condition in which broadcasts become so numerous as to bog down the flow of data across the network.

brouter

A device that can be used to combine the benefits of both routers and bridges. Its common usage is to route routable protocols at the network layer of the OSI model and to bridge nonroutable protocols at the data-link layer.

brownout

A short-term decrease in the voltage level, usually caused by the startup demands of other electrical devices.

buffer

An area of memory in a device that is used to store data before it is forwarded to another device or location.

bus

A path that is used by electrical signals to travel between the CPU and the attached hardware.

bus mastering

A bus accessing method in which the NIC takes control of the bus in order to send data through the bus directly to the system memory, bypassing the CPU.

bus topology

A linear LAN architecture in which all devices are connected to a common cable, referred to as a bus or backbone.

byte

A set of bits (usually 8 bits) that operate as a unit to signify a character.