netty 12

802.11

Specifications developed by IEEE for wireless networking over microwave radio transmission in the 2.4 GHz, 5 GHz, and 6 GHz frequency bands.

six main iterations:

• a, b, g, Wi-Fi 4 (n), Wi-Fi 5 (ac), and Wi-Fi 6 (ax).

• specify different modulation techniques, supported distances, and data rates, etc

csma/cd

Mechanism used by 802.11 Wi-Fi standards to cope with contention over the shared access media.

Request to Send (RTS) and Clear To Send (CTS) mechanism

frequency band

Portion of the microwave radio-frequency spectrum in which wireless products operate, such as 2.4 GHz band or 5 GHz band.

channel

Subdivision of frequency bands used by Wi-Fi products to allow multiple networks to operate at the same location without interfering with one another.

2.4ghz

Wi-Fi has a longer range and works better through walls and solid objects. However, it has fewer channels and is often crowded with other Wi-Fi networks and devices like Bluetooth, which can cause interference and slower speeds.

band is subdivided into up to 14 channels

channels 1, 6, and 11 do not overlap in the band

5 ghz

Wi-Fi has a shorter range and does not pass through walls as well. However, it has more available channels, less interference, and usually provides faster speeds at close range.

802.11a

a standard specifies use of the 5 GHz frequency band and a multiplexed carrier scheme called Orthogonal Frequency Division Multiplexing (OFDM).

54mbps

802.11b

uses the 2.4 GHz frequency band. It was released at the same time as 802.11a.

uses a signaling method called DSSS with CCK encoding. Its maximum speed was only about 11 Mbps, which was slower than the 802.11a.

more popular because they were released faster and were adopted more widely.

802.11g

was designed as an easy upgrade from 802.11b.

It uses the faster OFDM technology like 802.11a, but it still operates on the 2.4 GHz

54mbps

802.11n

Wi-Fi standard improves speed by using multiple antennas and a technology called MIMO (Multiple Input Multiple Output).

use 2.4ghz or 5ghz

allows channel bonding

72mbps

mimo

allows several data signals to be sent and received at the same time, which increases bandwidth and performance.

The antenna setup is written in a format like 2x2:2 or 4x4:4:

• The first number = transmit antennas

• The second number = receive antennas

• The third number = data streams that can be used at the same time

channel bonding

Capability to aggregate one or more adjacent wireless channels to increase bandwidth.

practical option only in the 5 GHz band.

802.11ac

wifi 5

designed to work only in the 5 GHz band. The 2.4 GHz band can be used for legacy standards (802.11g/n) in mixed mode.

get throughput like that of Gigabit Ethernet or better.

supports up to four stations in parallel over the 5 GHz band only mumimo

802.11ax

wifi 6

aims to approximate 10G connection speeds, significantly improving upon the throughput

uses advanced modulation and signal encoding to improve the amount of data sent per packet by about 40%.

1,148 Mbps on the 2.4 GHz radio and 4,804 over 5 GHz.

use of a new 6 GHz frequency band, which is required to achieve the highest data rates.

can support up to eight MU MIMO stations communicating in parallel across 2.4 GHz, 5 GHz, and 6 GHz bands,

mu-mimo

lets a wireless access point (AP) communicate with multiple devices at the same time using multiple antennas. This improves speed and performance, especially in crowded networks.

wifi 5/6

band steering

Feature of Wi-Fi that allows an access point to try to ensure that clients use a particular frequency band, such as 5 GHz rather than 2.4 GHz.

cellular radio

establishes a connection with the nearest available cell or base station. Each base station has an effective range of up to 5 miles (8 km). The base station links the device to global telecommunications networks.

lte

Packet data communications specification providing an upgrade path for both GSM and CDMA cellular networks.

150 Mbps in theory, but around 20 Mbps is typical of real-world performance.

5g

Rather than a single large antenna serving a large wireless cell, involves installing hundreds of smaller antennae to form massive MIMO.

20 gbps theoretical

satellite

System of microwave transmissions where orbital satellites relay signals between terrestrial receivers or other orbital satellites.

internet connectivity is enabled through a reception antenna connected to the PC or network through a DVB-S modem.

leo

satellites support better bandwidth (around 70–100 Mbps at the time of writing) and are lower latency (100–200 ms RTT).

satellites move relative to the surface of Earth. The customer's premises antenna must be provisioned with a motor so that it can periodically realign with the array.

ssid

A character string that identifies a particular wireless LAN (WLAN).

bssid

MAC address of an access point supporting a basic service area.

bss (basic service set)

AP mediates communications between client devices using a specific frequency and channel

ess (extended service se)

Network name configured on multiple access points to form an extended service area.

Each BSS uses a different channel within each frequency band. When deployed like this, the network name is more properly called an Extended SSID

wifi range

indoor range of at least 30 m (100 feet). 2.4 GHz radios support better ranges than 5 GHz ones, and 802.11n

rssi

is the strength of the signal from the transmitter as measured at the client end.

Signal strength as measured at the receiver, using either decibel units or an index value.

values closer to zero representing better performance. -30 dBm is considered to be a perfect signal.

snr

comparative strength of the data signal to the background noise is called the signal-to-noise ratio

wireless survey

Documentation about a location for the purposes of building an ideal wireless infrastructure; it often contains optimum locations for wireless antenna and access point placement to provide the required coverage for clients and identify sources of interference.

roam

means that wireless clients can remain connected to the same network ESSID while moving around within an extended service area (ESA).

ds (distribution system)

Connecting access points to a switched network via cabling to facilitate roaming within an extended service area (ESA). A wireless distribution system uses a access points configured in repeater mode to facilitate roaming.

wireless controller

Device that provides wireless LAN management for multiple APs.

ap

a hardware device that bridges a wired local area network (LAN) with Wi-Fi devices

• autonomous: firmware contains enough processing logic to be able to handle clients without the use of a wireless controller

• lightweight:requires a wireless controller in order to function. cisco

antenna type

Specially arranged metal wires that can send and receive radio signals

• omnidirectional: receives and sends signals in all directions more or less equally

• unidirectional: focused in a single direction. Both the sender and receiver must use directional antennae

• beamwidth: indicates the amount of directionality and is measured in degrees. A smaller beamwidth means the antenna is more directional, requiring more precise alignment.

polarization

refers to the orientation of the wave propagating from the antenna.

ibss

A type of wireless network where connected devices communicate directly with each other instead of over an established medium.

does not require an access point.

ad hoc topology, ex: shared printer

wmn (wireless mesh network)

Wireless network topology where all nodes—including client stations—are capable of providing forwarding and path discovery. This improves coverage and throughput compared to using just fixed access points and extenders.

foms mbss/mesh basic service set

point to point

usually used as a means of bridging two locations when it is not possible to connect them using cables.

establish a logical and physical connection between two devices

ad hoc

networks are direct connections between devices without an intermediary access point, less common for general Wi-Fi use.

infrastructure network

most common Wi-Fi setup, where devices connect through an access point. This setup provides a centralized point for data transmission and allows for greater range and connectivity options compared to other types.

wpa (wifi protected access)

Standards for authenticating and encrypting access to Wi-Fi networks.

uses the RC4 stream cipher to encrypt traffic but adds a mechanism called the Temporal Key Integrity Protocol (TKIP) to try to mitigate the various attacks against WEP that had been developed.

wpa2

AES cipher places RC4, and CCMP replaces TKIP.

CCMP provides authenticated encryption, which is designed to make replay attacks harder.

sae (simultaneous authentication of equals)

Personal authentication mechanism for Wi-Fi networks introduced with WPA3 to address vulnerabilities in the WPA-PSK method.

WPA3

AES GCMP replaces AES CCMP

Management frames are used for association and authentication and for disassociation and deauthentication messages as devices join and leave the network.

encrypts opne wifi

psk

A wireless network authentication mode where a passphrase-based mechanism is used to allow group authentication to a wireless network. The passphrase is used to derive an encryption key.

wpa2

enterprise authentication

A wireless network authentication mode where the access point acts as pass-through for credentials that are verified by an AAA server.

personal authentication

wireless network authentication

WPA2-Personal and WPA3-SAE ( WPA2-PSK and WPA3-Personal)

open authentication

Wireless network authentication mode where guest (unauthenticated) access is permitted.

byod

Security framework and tools to facilitate the use of personally owned devices to access corporate networks and data.

rogue ap

Wireless access point that has been enabled on the network without authorization.

evil twin

A wireless access point that deceives users into believing that it is a legitimate network access point.

deauthentication attack

Spoofing frames to disconnect a wireless station to try to obtain authentication data to crack.

rf attenuation

Loss of signal strength due to distance and environmental factors. Also referred to as free space path loss.

wifi analyzer

Device or software that can report characteristics of a WLAN, such as signal strength and channel utilization.

Antenna Cable Attenuation

Signal loss caused by an external antenna connected to an access point over coax cabling.

eirp

Signal strength from a transmitter, measured as the sum of transmit power, antenna cable/connector loss, and antenna gain.

channel overlap

refers to interference issues resulting from multiple access points that are all in range of one another and are configured to use similar wavelengths. There are two main types of channel interference:

• cci

• aci

cci (co channel interference)

Troubleshooting issue where access points within range of one another are configured to use the same channel, causing increased contention.

aci (adjacent channel interference

Troubleshooting issue where access points within range of one another are configured to use different but overlapping channels, causing increased noise. Also called channel overlap.

interference issues

• mirrors caausing relflections/bounces

• refraction from glass or water

• absoption from walls, windows, people

• emi from powerful radio or other source

spectrum analyzer

Device that can detect the source of interference on a wireless network.detects emi

dissaociation

Management frame handling process by which a station is disconnected from an access point.

roaming troubleshooting

• Sticky clients: Devices that stay connected to a weak Wi-Fi access point (AP) even when another nearby AP would give them a stronger, faster connection.

• Flapping clients: Devices that keep jumping back and forth between different Wi-Fi access points too often.

• Devices without roaming support (802.11k, r, v):

• Different coverage between 2.4 GHz and 5 GHz Wi-Fi

ap power

transmit power to 2/3rds of the weakest client's power helps balance the communication capabilities between the AP and client devices. This ensures that both the AP and the clients can effectively send and receive signals, reducing the likelihood of one-way communication issues and maintaining a stable connection.

inverse-square rule

distance between a transmitter and receiver is doubled, the signal strength is reduced by a factor of four, highlighting the rapid decrease in signal strength with increased distance.