AUI

Attachment Unit Interface. The 15-pin signal interface defined in the original Ethernet standard carries signals between a station and an outboard transceiver.

Authentication

Verification of the identity of the sender of a message – usually with a username and a password.

Auto-Negotiation

An Ethernet standard protocol allows devices at either end of a link to advertise and negotiate modes of operation such as the speed, half-or full-duplex operation and full-duplex flow control.

Auto-MDIX (Auto-Crossover)

A protocol allowing two Ethernet devices to negotiate their use of the Ethernet TX and RX cable pairs so two Ethernet devices can connect whether using a crossover cable or a straight-through cable.

B

Backbone
A network that joins smaller networks together.

Bandwidth
The maximum capacity of a network channel. Usually expressed in bits per second (bps). Ethernet channels have bandwidths of 10, 100, or 1000 Mbps.

Baud
A unit of signalling speed represents the number of discrete signal events per second and, depending upon the encoding, can differ from the bit rate.

Best-Effort Delivery
In IP, a transmission mechanism that does not guarantee message delivery.

Bit
A binary digit. The smallest unit of data, either a zero or a one.

Bit Rate
The amount of bits that can be sent per second. Usually described in units of kbps or Mbps and frequently referred to as the data rate.

Block Encoding
A system in which data bits are encoded as code bits to ensure synchronization and detection of errors – used in Fast Ethernet and Gigabit Ethernet.

Blocking
The condition in which a switching network is working at its full capacity and cannot accept more input.

Blocking Port
In STP and RSTP, a switch port that does not forward frames.

Bridge
A device with filtering and forwarding capabilities that connects two or more networks at the Data link Layer.

Broadcast
A transmission is initiated by one station and sent to all stations on the network.

Browser
An application that displays a Web document – typically with the aid of other Internet services.

Bus
A shared connection for multiple devices over a cable or backplane.

Byte
A unit of digital information – usually 8 bits. Originally, the bits needed to encode a text character. Historically, it was hardware dependent with no standard size. The term octet (8 bits) arose due to the ambiguity of the size of a byte.

C

Cable Modem
A device integrating switch and modem functions to deliver broadband Internet via coaxial cable to a local network.

Cache
Small, fast memory for holding data that is being processed.

Category 5
Twisted-pair cable with characteristics suitable for all twisted-pair Ethernet media systems – including 10BASE-T, 100BASE-TX and 1000BASE-T. Category 5 and Category 5e cable are preferred cable types for structured cabling systems.

Category 5e
An enhanced version of Category 5 cable, developed to improve certain cable characteristics important to Gigabit Ethernet operation. It is recommended that all new structured cabling systems be based on Category 5e cable; however, this cable may not be the best for use in industrial installations because of noise susceptibility.

Channel
A communications pathway.

Checksum
An error detection value is derived from the sum of a bitstream.