Glossary

Table of Contents

glossary
A
B
C
D
E
F
G
H
I
M
P
Q
R
S
T
V
W

glossary


802.11

The IEEE standard that specifies carrier sense media access control and physical layer specifications for 1- and 2-megabit-per-second (Mbps) wireless LANs.

802.11b

The IEEE standard that specifies carrier sense media access control and physical layer specifications for 5.5- and 11-Mbps wireless LANs.

A

 

Access Point

A wireless LAN data transceiver that uses radio waves to connect a wired network with wireless stations.

Ad Hoc Network

A wireless network composed of stations without Access Points.

Associated

A station is configured properly to allow it to wirelessly communicate with an Access Point.

B

 

BOOTP

Boot Protocol. A protocol used for the static assignment of IP addresses to devices on the network.

Beacon

A wireless LAN packet that signals the availability and presence of the wireless device. Beacon packets are sent by access points and bridges. Client adapters send beacons in AdHoc mode.

BPSK

A modulation technique used by IEEE 802.11-compliant wireless LANs for transmission at 1 Mbps.

Broadcast Key Rotation

When you enable broadcast WEP key rotation, the bridge provides a dynamic broadcast WEP key to associated devices and changes the key at the interval you select.

Broadcast Packet

Data packets that are sent to all nodes on a network. These packets are identified by a special broadcast address.

C

 

CCK

Complementary code keying. A modulation technique used by IEEE 802.11-compliant wireless LANs for transmission at 5.5 and 11 Mbps.

Cell

The area of radio range or coverage in which the wireless devices can communicate with the base station. The size of the cell depends upon the speed of the transmission, the type of antenna used, and the physical environment, as well as other factors.

Client

A radio device that uses the services of an Access Point to communicate wirelessly with other devices on a local area network.

CSMA

Carrier sense multiple access. A wireless LAN media access method specified by the IEEE 802.11 specification.

D

 

Data Rates

The range of data transmission rates supported by a device. Data rates are measured in megabits per second (Mbps).

Decibels (dB)

A unit for measuring relative power ratios in terms of gain or loss. Units are expressed in terms of the logarithm to base 10 of a ratio and typically are expressed in watts.

dBi

A ratio of decibels to an isotropic antenna that is commonly used to measure antenna gain. The greater the dBi value, the higher the gain, and the more acute the angle of coverage.

dBm

A ratio of decibels per milliwatt.

DHCP

Dynamic host configuration protocol. A protocol that allows a central device to automatically issues IP addresses within a specified range to devices on the network. The device retains the assigned address for a specific administrator-defined period.

Dipole

A type of low-gain (2.2-dBi) antenna consisting of two (often internal) elements.

Domain Name

The text name that refers to a grouping of networks or network resources based on organization-type or geography; for example: name.com—commercial; name.edu—educational; name.gov—government; ISPname.net—network provider (such as an ISP); name.ar—Argentina; name.au—Australia; and so on.

Dot address

Refers to the common notation for IP addresses in the form n.n.n.n where each number n represents, in decimal, 1 byte of the 4-byte IP address. Also referred to as dotted decimal address.

DSSS

Direct sequence spread spectrum. A type of spread spectrum radio transmission that spreads its signal continuously over a wide frequency band.

E

 

EAP

Extensible Authentication Protocol. An optional IEEE 802.1x security feature ideal for organizations with a large user base and access to an EAP-enabled Remote Authentication Dial-In User Service (RADIUS) server.

EIRP

Effective Isotropic Radiated Power. A term for expression of the performance of an antenna in a given direction relative to the performance of a theoretical (isotropic) antenna and is expressed in watts. EIRP is the sum of the power sent to the antenna plus antenna gain.

Ethernet

The most widely used wired local area network. Ethernet uses carrier sense multiple access (CSMA) to allow computers to share a network and operates at 10, 100, or 1000 Mbps, depending on the physical layer used.

F

 

File Server

A repository for files so that a local area network can share files, mail, and programs.

Firmware

Software that is programmed on a memory chip.

Full duplex

The capability for simultaneous data transmission between a sending station and a receiving station (both directions at the same time).

G

 

Gateway

A device that connects two otherwise incompatible networks together.

GHz

Gigahertz. One billion cycles per second. A unit of measure for frequency.

H

 

Half duplex

The capability for data transmission in only one direction at a time between a sending station and a receiving station.

I

 

IEEE

Institute of Electrical and Electronic Engineers. A professional society serving electrical engineers through its publications, conferences, and standards development activities. The body responsible for the Ethernet 802.3 and wireless LAN 802.11 specifications.

Infrastructure

The wired Ethernet network.

IP Address

The Internet Protocol (IP) address of a station. A 32-bit address that is written as 4 octets separated by periods (dotted decimal format). Each address consists of a network number, an optional subnetwork number, and a node number. The network and subnetwork numbers together are typically used for routing, and the node number is used to address an individual node within the network or subnetwork. A subnet mask is used to extract network and subnetwork information from the IP address.

IP Subnet Mask

A 32-bit address mask used to indicate the bits of an IP address that are being used for the subnet address. The subnet mask is used to indicate whether the IP address can be reached on the local LAN or if it must be routed through a gateway.

Isotropic

An antenna that radiates its signal 360 degrees both vertically and horizontally in a perfect sphere.

M

 

MAC

Media Access Control. A unique 48-bit number used in Ethernet data packets to identify an Ethernet device, such as the bridge.

MIC

MIC (Message Integrity Check) prevents attacks on encrypted packets called bit-flip attacks. During a bit-flip attack, an intruder intercepts an encrypted message, alters it slightly, and retransmits it, and the receiver accepts the retransmitted message as legitimate. The MIC, implemented on both the bridge and all associated client devices, adds a few bytes to each packet to make the packets tamper-proof.

Modulation

Any of several techniques for combining user information with a transmitter's carrier signal.

Multicast Packet

A single data message (packet) sent to multiple end nodes.

Multipath

The echoes created as a radio signal bounces off of physical objects.

P

 

Packet

A basic message unit for communication across a network. A packet usually includes routing information, data, and sometimes error detection information.

Q

 

Quadruple Phase Shift Keying

A modulation technique used by IEEE 802.11-compliant wireless LANs for transmission at 2 Mbps.

Quality of Service (QoS)

The ability of a network to provide improved service to selected network traffic over various underlying technologies including Ethernet and wireless LANs.

R

 

Range

A linear measure of the distance that a transmitter can send a signal.

Receiver Sensitivity

A measurement of the weakest signal a receiver can receive and still correctly translate it into data.

RF

Radio frequency. A generic term for radio-based technology.

Roaming

A feature of some Access Points that allows users to move through a facility while maintaining an unbroken connection to the LAN.

Root Bridge

A point that is located at the top, or starting point, of a wireless infrastructure. A root bridge provides the physical connection to the main wired LAN and only accepts associations from non-root bridges, access points, and client devices. A root bridge cannot associate with another root bridge.

RP-TNC

A connector type unique to Cisco Aironet radios and antennas. Part 15.203 of the FCC rules covering spread spectrum devices limits the types of antennas that may be used with transmission equipment. In compliance with this rule, Cisco Aironet, like all other wireless LAN providers, equips its radios and antennas with a unique connector to prevent attachment of non-approved antennas to radios.

S

 

Spread Spectrum

A radio transmission technology that spreads the user information over a much wider bandwidth than otherwise required in order to gain benefits such as improved interference tolerance and unlicensed operation.

SSID

Service Set Identifier. A unique identifier that stations must use to be able to communicate with an Access Point. The SSID can be any alphanumeric entry up to a maximum of 32 characters.

Subnet Mask

A value used with an IP address to identify a sub-network. This value is expressed in a form similar to an IP address. For example, 255.255.0.0.

T

 

TKIP

TKIP (Temporal Key Integrity Protocol, also known as WEP key hashing) defends against an attack on WEP in which the intruder uses the unencrypted initialization vector (IV) in encrypted packets to calculate the WEP key. TKIP removes the predictability that an intruder relies on to determine the WEP key by exploiting IVs.

Transmit Power

The power level of the radio transmission.

V

 

Virtual Local Area Network (VLAN)

A switched network that is logically segmented into virtual local-area networks on a physical or geographical basis, or by functions, project teams, or applications.

W

 

WEP

Wired Equivalent Privacy. An optional security mechanism defined within the 802.11 standard designed to make the link integrity of wireless devices equal to that of a cable.

Workstation

A computing device with an installed client adapter.