Aironet Desktop Utility (ADU) Cisco software used to manage a single a/b/g wireless card.
Airport Extreme The MAC-OSX wireless client.
amplifier Added between the AP and the antenna to strengthen the signal.
amplitude The volume of the signal.
anchor The original controller.
Announcement Traffic Indication Message (ATIM) Used in IEEE 802.11 ad hoc or
independent BSS networks to announce the existence of buffered frames when a client is in
sleep mode.
AP priming After the AP is associated with at least one controller, the AP gets a list of
other controllers it can associate with from the one that is already associated with.
ARP Address Resolution Protocol. Used to resolve a MAC address to an IP address.
association request A request from a client to the AP for association.
association response A response from an AP to a client during open association.
asymmetric tunneling Traffic from the client is routed to the destination, regardless of its
source address. The return traffic is sent to its original controller, called an anchor, and is tun-
neled to the new controller.
attenuator Reduces the signal if there is too much signal, causing bleed-over into other
networks.
authentication request A request from a client to an AP during open authentication.
authentication response A response from an AP to a client during open authentication.
authentication server An AAA server that has a list of users in one form or another that
can verify the supplicant.
authenticator The switch.
Autonomous Workgroup Bridge (aWGB) A wireless bridge operating autonomously.
autoprovisioning Simplifies deployments when you have a large number of controllers.
azimuth The angle measured in degrees between a reference plane and a point.
B
backoff timer A random number that begins a countdown process while listening.
bandwidth The frequency spectrum, measured in Hertz. Bandwidth can refer to data rates
or the width of an RF channel.
barker code Defines the use of 11 chips when encoding data.

Basic Service Area (BSA) The coverage area of the AP.
Basic Service Set (BSS) One device sets a network name and radio parameters, and the
other uses it to connect.
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Basic Service Set Identifier (BSSID) Only one network that an AP is offering service for.
beacon An announcement of services from an AP.
Binary Phase Shift Keying (BPSK) A modulation technique used in 802.11 networks.
block acknowledgment The confirmation from the recipient station, stating which frames
have been received. Used in 802.11n networks.
Bluetooth A personal-area technology.
bridge mode A mode that an AP can operate in, in which it bridges traffic from source to
destination.
C
Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) When a device
wants to send, it must listen first. Similar to CSMA/CD.
channel A defined frequency range.
Channel State Information (CSI) If the receiver is moving, the reflection characteristics
change, and the beamforming can no longer be coordinated.
chipping code A code used to represent bits.
circular polarization Indicates that the wave circles as it moves forward.
Cisco Client Extension Program (CCX) A no-cost licensing of technology for use in
WLAN adapters and devices.
Cisco Configuration Assistant (CCA) A software application used to set up mobility
express networks.
Cisco Discovery Protocol (CDP) A Cisco-proprietary protocol that can gain information
about directly connected Cisco devices.
Cisco Site Survey Utility (CSSU) The optional software set that you select with a check-
box during installation.
Cisco Smart Business Communication System (SBCS) The Cisco solution for voice,

video, and wireless for the small business.
Cisco Wireless Location Appliance Maps clients and helps enforce security policies.
Cisco Wizard Configuration Tool A wizard-type menu used to perform basic configura-
tion.
Clear Channel Assessment (CCA) A function found within physical layers that deter-
mines the current state of use of a wireless medium.
Clear-To-Send (CTS) A message indicating that it is clear to send data on the wireless
medium.
Clear-To-Send to self (CTS to self) A method indicating that it is clear to send data on a
wireless network.
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client MFP If the client is running CCX 5 or better, it can actually talk to the AP and find
out what the MIC is.
co-channel interference Crosstalk between channels that are next to each other.
Code Division Multiple Access (CDMA) A channel access method.
community A group name for your mobility express network.
Complementary Code Keying (CCK) Uses a series of codes called complementary
sequences.
contention window The total amount of time that Station A waits before sending.
control frame Used to acknowledge when data frames are received.
CSSC Cisco Secure Services Client software.
D
data frame A frame that contains data.
deauthentication message When a client is connected to a wireless cell, either the client
or the AP can leave the connection by sending this message. This message has information in
the body about why it is leaving.
deauthentication response A response to a deauthentication message.
destination address (DA) A frame’s final destination.
Digital Enhanced Cordless Telecommunications (DECT) An ETSI standard for digital

portable phones. Found in cordless technology that is deployed in homes or business.
dipole See rubber duck.
directional antenna Mounted on a wall. Its radiation pattern is focused in a certain direction.
Direct Sequence Spread Spectrum (DSSS) The modulation technique used by 802.11b
devices to send data. The transmitted signal is spread across the entire frequency spectrum
that is being used.
disassociation message Disassociates from the cell but keeps the client authenticated.
disassociation response A response to a disassociation message.
Distributed Coordination Function (DCF) Each station is responsible for coordinating
the sending of its data.
Distributed Interframe Space (DIFS) Each sending station must wait after a frame is sent
before sending the next frame.
distribution system The AP connects to a distribution system to get to server farms, the
Internet, and other subnets.
diversity vertical polarization The use of two antennas for each radio to increase the
odds of receiving a better signal on either of the antennas.
dual-patch “omnidirectional” Two patch directional antennas are placed back to back,
making it “omnidirectional.”
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Dynamic Frequency Control (DFC) The ability to change frequency to avoid radar sig-
nals.
dynamic interface Includes the user-defined list.
Dynamic Rate Shifting (DRS) The capability of a wireless network to shift to a lower rate
as a client moves farther away from the AP.
E
Effective Isotropic Radiated Power (EIRP) Used to estimate the service area of a device.
The formula is as follows:
EIRP = transmitter – cable loss + antenna gain
elevation plane (E-plane) The vertical pattern does not propagate evenly.

Enhanced Data Rate (EDR) A Bluetooth 2.0 feature providing up to three times the band-
width for Bluetooth clients.
exposed node issue When there are two wireless cells on the same channel and they are
too close to each other.
Extended Rate Physical (ERP) Devices that have extended data rates.
Extended Service Area (ESA) More than one AP is connected to a common distribution
system.
Extensible Authentication Protocol (EAP) Controls the authentication process under the
premise that no matter what EAP method you use, the basic steps will reamain the same.
Extensible Authentication Protocol-Flexible Authentication via Secure Tunnel (EAP-
FAST) Created to address weaknesses in Lightweight Extensible Authentication Protocol
(LEAP). Uses PAC, not PKI.
Extensible Authentication Protocol-Transport Layer Security (EAP-TLS) A common-
ly used EAP method for wireless networks.
European Telecommunications Standards Institute (ETSI) Produces globally applica-
ble standards for Information and Communications Technologies (ICT), including fixed,
mobile, radio, converged, broadcast, and Internet technologies.
F
Federal Communications Commission (FCC) An independent U.S. government agency
established by the Communications Act of 1934. It regulates interstate and international com-
munications by radio, television, wire, satellite, and cable. The FCC’s jurisdiction covers the
50 states, the District of Columbia, and U.S. possessions.
Frame Check Sequence (FCS) Extra checksum characters added to a frame in a commu-
nication protocol for error detection and correction.
free path loss The loss in signal strength of an electromagnetic wave that results from a
line-of-sight path through free space, where no obstacles are nearby to cause reflection or
diffraction.
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frequency The pitch of the signal.

Frequency Division Multiple Access (FDMA) An access technology that radio systems
use to share the radio spectrum, commonly found in 802.11 networks.
Frequency Hopping Spread Spectrum (FHSS) A spread spectrum method in which the
signal hops between channels. If a channel experiences interference, it can be skipped.
G
Generic Token Card (GTC) Authenticates the user inside an encrypted tunnel.
Global System for Mobile Communication (GSM) A digital mobile telephony system
that uses a variation of time-division multiple access (TDMA). The most widely used of the
three digital wireless telephony technologies (TDMA, GSM, and CDMA). GSM operates at
either the 900-MHz or 1800-MHz frequency band.
Group Master Key (GMK) Used by the AP to generate a group random number.
Group Temporal Key (GTK) Generated by the GMK random number. Provides a group
key and a MIC. This key changes when it times out or when a client leaves the network.
Group Transient Key (GTK) Used to decrypt broadcast and multicast.
H
Hertz (Hz) Used to measure bandwidth. Hertz measures the number of cycles per second.
One Hertz is one cycle per second.
hidden node issue When more than one client tries to send on the same channel at the
same time. They are in range of the AP but not each other.
hidden node problem When two devices cannot hear each other.
horizontal plane (H-plane) The horizontal plane of an omnidirectional polarized antenna,
opposite the E-plane.
horizontal polarization The wave goes left and right in a linear way.
hybrid REAP mode Hybrid Remote Edge Access Point (H-REAP) is a solution for branch
office and remote office deployments. It lets you configure access points (AP) in a branch or
remote office from the corporate office through a wide-area network (WAN) link without the
need to deploy a controller in each office.
I
Independent Basic Service Set (IBSS) When two machines do not need a central device
to speak to each other.

Industry, Scientific, and Medical (ISM) frequency bands Use of spread spectrum in
the commercial market.
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infrastructure Refers to assets that support a network.
infrastructure device The access point (AP).
infrastructure MFP Management Frame Protection performed by APs.
initialization vector (IV) A block of bits that is used to produce a unique encryption key.
Institute for Electrical and Electronics Engineers (IEEE) A nonprofit organization,
IEEE is the world’s leading professional association for the advancement of technology.
intercontroller roaming When a user roams from one controller to another but remains on
the same VLAN.
interface The logical, dynamic, or static port of a network device. Also refers to VLANs.
interframe spacing (IFS) A period of time that a station has to wait before it can send.
intracontroller roaming When roaming is handled within a single controller.
IP Setup utility Takes the MAC address of the AP and resolves the IP address associated
with it.
isotropic radiator A reference that assumes that the signal is propagated evenly in all direc-
tions. This would be a perfect 360-degree sphere in all directions, on the H- and E-planes.
iwconfig The command-line tool for Linux to work with WLANs.
J–K
join request message A message sent by an AP to join a wireless controller.
L
Layer 3 LWAPP mode The default LWAPP mode on most Cisco devices.
lightning arrestor Prevents surges from reaching the RF equipment by the device’s shunt-
ing effect.
Lightweight Access Point Protocol (LWAPP) A protocol used for communication
between a lightweight AP and a wireless controller.
lightweight AP An AP that receives configuration from a controller and cannot function
without the controller.

Lightweight Extensible Authentication Protocol (LEAP) Uses a proprietary algorithm
to create the initial session key.
Line-of-Sight (LOS) The signal between the two points that appears to be a straight shot.
link budget A value that accounts for all the gains and losses between sender and receiver.
It accounts for attenuation, antenna gain, and other miscellaneous losses that may occur.
local mode The standard operating mode of an access point.
LWAPP discovery request An LWAPP message used to discover a controller.
LWAPP discovery response A response from a controller to an AP during discovery.
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M
management frame Used to join and leave a wireless cell.
Management Frame Protection (MFP) A method used to detect spoofed management
frames in which valid frames contain a hash that spoofed frames would not.
master controller Configured in the GUI interface by choosing CONTROLLER >
Advanced > Master Controller Mode.
Maximum Transmission Unit (MTU) The largest frame size supported on an interface.
Message Integrity Check (MIC) A cryptographic hash in each management frame used
to ensure that data is not tampered with.
Microsoft Challenge Handshake Authentication Protocol version 2 (MS-CHAPv2) A
protocol used to authenticate the user inside an encrypted tunnel in Microsoft Windows
Active Directory.
mobility anchor A feature in which all the client traffic that belongs to a WLAN (especial-
ly the guest WLAN) is tunneled to a predefined WLC or a set of controllers that are config-
ured as an anchor for that specific WLAN. Also called guest tunneling or auto-anchor mobility.
mobility domain A controller can be aware of another controller in a different mobility
group.
mobility group A setting that defines the controller as a member of a group.
monitor mode A mode that an AP can operate in where it constantly scans all channels to
perform rouge detection. When in this mode, the AP cannot service clients.

multipath Defines when portions of signals are reflected and then arrive out of order at the
receiver.
Multiple Basic Service Set Identifier (MBSSID) Used when the AP has more than one
network.
Multiple-Input Multiple-Output (MIMO) A technology that is used in the new 802.11n
specification. A device that uses MIMO technology uses multiple antennas to receive signals,
usually two or three, as well as multiple antennas to send signals.
N
N+1 A method of controller redundancy—a controller plus one for backup.
N+N Two active controllers that can back each other up.
N+N+1 Two controllers backing each other up, with a dedicated backup as a last resort.
native VLAN The VLAN on a trunk that does not get tagged.
NAV Norton AntiVirus.
N connector A type of antenna connector.
network manager A graphical user interface (GUI) tool that enables the creation of wire-
less profiles in Linux.
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node Another term for an access point in a mesh network.
null function frame The client wakes up after a certain period of time, during which the
AP buffers any traffic for it.
NVRAM Nonvolatile RAM. A storage location used to keep configuration files.
O
omnidirectional antenna An antenna type that does not focus a signal in one direction.
one-floor concept The signal propagates wider from side to side than from top to bottom.
Therefore, the signal can offer coverage to the floor it is placed on rather than to the floor
above or below the AP.
Orthogonal Frequency Division Multiplexing (OFDM) Defines a number of channels in
a frequency range. Not considered a spread spectrum technology but is used for modulation
in a wireless network.

Over-the-Air Provisioning (OTAP) A method for APs to discover the management IP of a
controller over the air.
P
Pairwise Master Key (PMK) A wireless security key.
Pairwise Transient Key (PTK) This type of key confirms the PMK between two devices,
establishes a temporal key to be used for message encryption, authenticates the negotiated
parameters, and creates keying material for the next phase, called the two-way group key
handshake.
parabolic dish Has a very narrow path and is very focused in its radiation pattern.
passive scan A scan in which wireless clients mark the channels on which a beacon is
heard.
phase The timing of the signal between peaks.
Point Coordination Function (PCF) The AP is responsible for coordinating the sending of
its data.
polarity The direction in which the RF is sent from an antenna—horizontal or vertical.
port A physical interface on your controller.
precoding A function that takes advantage of multiple antennas and the multipath issue.
probe request A client request for an AP.
probe response A response to a probe request.
protected EAP (PEAP) Only a server-side certificate is used to create a tunnel, and then
the real authentication takes place inside.
PS-poll Power-save poll.
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Q–R
Quadrature Phase Shift Keying (QPSK) A version of frequency modulation in which the
phase of the carrier wave is modulated to encode bits of digital information in each phase
change.
radiation pattern The direction of the RF propagation.
Radio Resource Management (RRM) A software feature of the Cisco controller that acts

as a built-in RF engineer to consistently provide real-time RF management of your wireless
network.
RAM Random-access memory, used during operation. Lost when the system reloads.
Real-Time Operating System (RTOS) The controller’s operating system.
Receiving Address (RA) The address of the direct station that this frame is sent to.
Reduced Interframe Space (RIFS) A smaller interframe space, reducing delay and over-
head.
reflection Happens when a signal bounces off something and travels in a different direc-
tion.
refraction The change in direction or the bending of a waveform as it passes through some-
thing that has a different density.
repeater A device that repeats a signal to extend distance.
Request-To-Send (RTS) A request to send on a wireless network.
response In a wireless LAN, a response to a request for connectivity.
Reverse-Polarity Threaded Neill-Concelman (RP-TNC) A type of antenna connector.
roaming A client moving from one AP to another AP, overlapping.
rogue detector mode A mode an AP can operate in to look for rogue devices. When
operating in this mode, an AP looks on the wireless network for ARP messages from rogue
devices.
rubber duck A common wireless antenna in a rubber sheath.
S
scattering The signal is sent in many different directions. This can be caused by an object
that has reflective yet jagged edges, or dust particles in the air and water.
Secure Services Client Administration Utilities (SSCAU) A component of Cisco
Secure Services Client (SSC) client software that enables the administrator to create complex
profiles.
Service Set Identifier (SSID) The name of a wireless network.
Short Interframe Space (SIFS) For higher priority. Used for ACKs, among other things.
Signal-to-Noise Ratio (SNR) How much stronger the signal is compared to the surround-
ing noise that corrupts it.

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site survey A measurement of a certain point in time—the time when you did the site
survey.
slottime The speed at which the backoff timer countdown occurs.
Small to Mid-Size Business (SMB) A business that has customers seeking to gain a com-
petitive edge without having to compromise between price and sophistication.
sniffer mode A mode that an AP can operate in to capture data and forward 802.11 pack-
ets to an application such as Wireshark for analysis.
sniff subrating Increases battery life up to five times.
source address (SA) The stations that sent the frame.
spatial multiplexing Takes a signal, splits it into a bunch of lower-rate streams, and then
sends each one out different antennas.
Special Interest Group (SIG) A Bluetooth group.
splitter Used in outdoor wireless deployments to split in two a signal coming from a cable,
and send it in two directions.
static interface Includes management interface, AP-Manager, service port.
station (STA) The client on a network.
supplicant A device that can use an EAP method to prove its identity to the authentication
server.
symmetric tunneling All traffic is tunneled from the client to the anchor controller, sent to
the destination, returned to the anchor controller, and then tunneled back to the client via the
foreign controller.
T
Temporal Key Integrity Protocol (TKIP) A method of automatically changing the keys.
TFTP Trivial File Transfer Protocol. Used to copy files between a client and server using
UDP port 69.
Time Division Multiple Access (TDMA) An access method that allocates time slots to
access the network.
Traffic Indication Map (TIM) This field indicates whether the AP is buffering traffic for

clients in power-save mode.
Transmit Beamforming (TxBF) A technique that is used when there is more than one
transmit antenna. The signal is coordinated and sent from each antenna so that the signal at
the receiver is dramatically improved, even if it is far from the sender.
Transmit Power Control (TPC) The ability to adjust power dynamically, and a require-
ment for use in the UNII bands.
Transmitter Address (TA) The address of the station that is emitting the frame.
trunk port A port that carries traffic for multiple VLANs by tagging traffic from each
VLAN.
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