Chapter 6 Key terms
wireless range extender
A device that extends the reach of a wireless signal by repeating the signal from a closer broadcast point.
wireless spectrum
A continuum of electromagnetic waves used for data and voice communication.
WLAN (wireless local area network)
A LAN that uses wireless connections for some or all of its transmissions.
wireless controller
A central management console for all the APs on a network.
iwconfig
A command-line utility for viewing and setting wireless interface parameters on Linux and UNIX workstations.
AP (access point)
A device used on wireless LANs that accepts wireless signals from multiple nodes and retransmits them to the rest of the network.
NFC (near-field communication)
A form of radio communication that transfers data wirelessly over very short distances (usually 10 cm or less).
ESS (extended service set)
A group of access points and associated stations (or basic service sets) connected to the same LAN.
WEP (Wired Equivalent Privacy)
A key encryption technique for wireless networks that uses keys both to authenticate network clients and to encrypt data in transit.
Bluetooth
A low-power wireless technology that provides close-range communication between devices such as PCs, smartphones, tablets, and accessories.
DSSS (direct sequence spread spectrum)
A modulation technique that, like other spread-spectrum technologies, distributes lower-level signals over several frequencies simultaneously.
CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance)
A network access method used on 802.11 wireless networks. CSMA/CA does not eliminate, but minimizes, the potential for collisions.
on-boarding
A process of configuring clients for wireless access to a network.
frequency hopping
A process performed by some wireless devices to help reduce interference by quickly hopping between frequencies within a given band of frequencies.
CAPWAP (Control and Provisioning of Wireless Access Points)
A proprietary protocol created by Cisco to replace LWAPP. Both LWAPP and CAPWAP make centralized wireless management possible.
WPAN (wireless PAN)
A purely wireless version of a PAN.
MAC filtering
A security measure that prevents an AP or a switch from authenticating any device whose MAC address is not listed by the network administrator as an approved device.
remote wipe
A security procedure that clears a device of all important information, permissions, and programs without having physical access to the device.
guest network
A separate wireless network created through a Wi-Fi router or access point to protect a private network while still providing guests with access to the Internet.
Z-Wave
A smart home protocol that provides two basic types of functions: signaling, to manage wireless connections, and control, to transmit data and commands between devices.
spectrum analyzer
A software tool that assesses the characteristics (for example, frequency, amplitude, and the effects of interference) of wireless signals.
ESSID (extended service set identifier)
A special identifier shared by BSSes that belong to the same ESS.
band
A specific frequency range on the wireless spectrum.
LLC sublayer
A sublayer of Layer 2 that is primarily concerned with multiplexing, flow and error control, and reliability.
paired
A term used to describe two Bluetooth devices that are communicating with each other.
omnidirectional antenna
A type of antenna that issues and receives wireless signals with equal strength and clarity in all directions.
unidirectional antenna
A type of antenna that issues wireless signals along a single direction, or path. Also called a directional antenna.
ad hoc
A type of wireless LAN in which stations communicate directly with each other (rather than using an access point).
infrastructure
A type of wireless network in which stations communicate through an access point and not directly with each other.
SSID (service set identifier)
A unique character string used to identify an access point on an 802.11 network.
fading
A variation in a wireless signal's strength as a result of some of the electromagnetic energy being scattered, reflected, or diffracted after being issued by the transmitter.
mesh
A wireless network in which multiple APs work as peer devices on the same network, thereby providing more fault-tolerant network access to clients.
LWAPP (Lightweight Access Point Protocol)
A wireless protocol created by Cisco that makes centralized wireless management possible.
WPA (Wi-Fi Protected Access or Wireless Protected Access)
A wireless security method that dynamically assigns every transmission its own key.
WPA2
A wireless security method that improves upon WPA by using a stronger encryption protocol called AES.
LOS (line of sight)
A wireless signal or path that travels directly in a straight line from its transmitter to its intended receiver.
FHSS (frequency hopping spread spectrum)
A wireless signaling technique in which a signal jumps between several different frequencies within a band in a synchronization pattern known to the channel's receiver and transmitter.
IR (infrared)
A wireless technology that uses a bandwidth just below the spectrum that is visible to the human eye, with longer wavelengths than red light.
RFID (Radio Frequency Identification)
A wireless technology that uses electromagnetic fields to store data on a small chip in a tag, which includes an antenna that can both transmit and receive, and possibly a battery.
data frame
An 802.11 frame type that is responsible for carrying data between stations.
wireless bridge
An access point used to create remote wired access to a network.
brute force attack
An attempt to discover an encryption key or password by trying numerous possible character combinations until the correct combination is found.
RTS/CTS (Request to Send/Clear to Send)
An exchange in which a source node requests the exclusive right to communicate with an access point and the access point confirms that it has granted that request.
evil twin
An exploit in which a rogue access point masquerades as a legitimate access point, using the same SSID and potentially other identical settings.
ANT+
An open-source wireless technology that gathers and tracks information from sensors typically embedded in heart rate monitors, GPS devices, and other activity monitoring devices.
rogue access point
An unauthorized access point in the same vicinity as a legitimate network.
IoT (Internet of Things)
Any device connected to the Internet.
interference
Degradation of a wireless signal caused by electromagnetic waves in the atmosphere.
BSS (basic service set)
In IEEE terminology, a group of stations that share an access point.
BSSID (basic service set identifier)
In IEEE terminology, the identifier for a BSS (basic service set).
MU-MIMO (multiuser MIMO)
In the context of 802.11ac wireless networking, the ability for access points to use multiple antennas in order to issue multiple signals to different stations at the same time, thereby reducing congestion and contributing to faster data transmission.
channel bonding
In the context of 802.11n and 802.11ac wireless technology, the combination of two or more adjacent 20-MHz frequency bands to create one 40-, 60-, 80-, or 120-MHz channel.
MIMO (multiple input-multiple output)
In the context of 802.11n/ac wireless networking, the ability for access points to use multiple antennas in order to issue multiple signals to stations, thereby multiplying the signal's strength and increasing their range and data-carrying capacity.
beacon frame
In the context of wireless networking, a frame issued by an access point to alert other nodes of its existence.
site survey
In the context of wireless networking, an assessment of client requirements, facility characteristics, and coverage areas to determine an access point arrangement that will ensure reliable wireless connectivity within a given area.
association
In the context of wireless networking, the communication that occurs between a wireless client and an access point enabling the client to connect to the network via that access point.
reassociation
In the context of wireless networking, the process by which a station establishes a connection with (or associates with) a different access point.
diffraction
In the context of wireless signal propagation, the phenomenon that occurs when an electromagnetic wave encounters an obstruction and splits into secondary waves.
reflection
In the context of wireless signaling, the phenomenon that occurs when an electromagnetic wave encounters an obstacle and bounces back toward its source.
refraction
In the context of wireless signaling, the way in which a wave alters its direction, speed, and wavelength when it travels through different transmission mediums.
war driving
The act of driving around an area while running a laptop configured to detect and capture wireless data transmissions.
Wi-Fi
Software that can evaluate Wi-Fi network availability as well as help optimize Wi-Fi signal settings or help identify Wi-Fi security threats.
Wi-Fi analyzer
Software that can evaluate Wi-Fi network availability as well as help optimize Wi-Fi signal settings or help identify Wi-Fi security threats.
802.11g
The IEEE standard for a wireless networking technique designed to be compatible with 802.11b in the 2.4-GHz frequency range while using different data modulation techniques that allow it to reach a theoretical maximum capacity of 54 Mbps.
802.11ac
The IEEE standard for a wireless networking technique that exceeds benchmarks set by earlier standards by increasing its useful bandwidth and amplitude. 802.11ac is the first Wi-Fi standard to approach Gigabit Ethernet capabilities.
802.11n
The IEEE standard for a wireless networking technique that may issue signals in the 2.4-GHz or 5-GHz band and can achieve actual data throughput between 65 Mbps and 600 Mbps.
802.11b
The IEEE standard for a wireless networking technique that uses DSSS (direct-sequence spread spectrum) signaling in the 2.4-GHz frequency range and provides a theoretical maximum throughput of 11 Mbps.
802.11a
The IEEE standard for a wireless networking technique that uses multiple frequency bands in the 5-GHz frequency range and provides a theoretical maximum throughput of 54 Mbps.
scattering
The diffusion, or the reflection in multiple directions, of a wireless signal that results from hitting an object with a rough surface or small dimensions compared to the signal's wavelength.
captive portal
The first page displayed by a client's browser when the client connects to a guest network. This page usually requires the user to agree to a set of terms and conditions before gaining further access to the guest network.
range
The geographical area in which signals issued from an antenna or wireless system can be consistently and accurately received.
MAC sublayer
The lower portion of the Data Link layer that is specifically involved with managing MAC addresses in message frames.
scanning
The process by which a wireless station finds an access point.
authentication
The process of comparing and matching a client's credentials with the credentials in a client database to enable the client to log on to the network.
SNR (signal-to-noise ratio)
The proportion of noise to the strength of a signal.
radiation pattern
The relative strength over a threedimensional area of all the electromagnetic energy an antenna sends or receives.
off-boarding
The reverse process of on-boarding, involving the removal of programs that gave a device special permissions on the network.
encryption
The use of an algorithm to scramble data into a format that can be read only by reversing the algorithm—that is, by decrypting the data—to keep the information private.
propagation
The way in which a wave travels from one point to another.
