802.11a
5 GHz
54 Mbit/s max
OFDM
35 m
Channels (nonoverlapped) 23(12)
max speed distance 65-75 ft
max distance 190 ft
802.11b
2.4 GHz
11 Mbit/s Max
DSSS
38 m
Channels (nonoverlapped) 11(3)
max speed distance 150 ft
max distance 350 ft
802.11g
2,4 GHz
54 Mbit/s max
OFDM, DSSS(11 Mbit/s)
38 m
Channels (nonoverlapped) 11(3)
max speed distance 90 ft
max distance 300 ft
802.11h - Extension of the 802.11a
23 non-overlapping channels
5 GHz
54 Mbit/s max
OFDM
35 m.
Two extensions: Transmit Power Control (TPC) and Dynamic Frequency Selection (DFS).
DFS – monitors operating channel, if it discovers signal, than it abandon this range.
TPC – regulates transmit power.
Security standards
WEP (Wired Equivalent Privacy)
It uses the stream cipher RC4 for confidentiality and the CRC-32 checksum for integrity.
Two methods of authentication can be used with WEP: Open System authentication and Shared Key authentication.
Static Preshared Keys (PSK), than nobody changes
Easily cracked keys: only 64 bits and only 40 from them are unique.
Remedies: SSID Cloaking and MAC Filtering.
WPA (Wi-Fi Protected Access)
It includes the option to use dynamic key exchange, using the Temporal Key Integrity Protocol (TKIP) and Message Integrity Check (MIC) algorithm.
WPA (Wi-Fi Protected Access)2(802.11i):
Dynamic key exchange
802.1x authentication
AES encryption
Classes of encoding
Frequency Hopping Spread Spectrum (FHSS) - not in use now days.
Direct Sequence Spread Spectrum (DSSS) This band has a bandwidth of 82 MHz, with a range from 2.402 GHz to 2.483 GHz. This band can have 11 different overlapping DSSS channels. 1,6 and 11 channels are nonoverlapping. Designed for 2,4 Ghz.
Orthogonal Frequency Division Multiplexing (OFDM)
Modes of operating
Ad-hoc. It uses Independent Basic Service Set (IBSS).
Infrastructure. Devices in an infrastructure WLAN cannot send frames directly to each other; instead, they send frames to the AP, which can then in turn forward the frames to another WLAN device.Infrastructure mode supports two sets of services, called service sets. The first, called a Basic Service Set (BSS), uses a single AP to create the wireless LAN. The other, called Extended Service Set (ESS), uses more than one AP, often with overlapping cells to allow roaming in a larger area.
Possible reasons of bad signals
Cordless phones
metal file cabinets
antenna type or direction
Other
Adaptive Wireless Path Protocol (AWPP) is a Cisco's proprietary protocol for wireless mesh networks. It dynamically discovers neighboring radios and calculates the quality of all possible paths to a wired network. An optimal path is established through a mesh of wireless nodes to a wired gateway and these calculations are continuously updated, allowing paths to change and optimize as traffic patterns on wireless links change. Furthermore, a self-configuring and self-healing wireless mesh backhaul is created.
Lightweight Access Point Protocol or LWAPP is the name of a protocol that can control multiple Wi-Fi wireless access points at once. This can reduce the amount of time spent on configuring, monitoring or troubleshooting a large network. The system will also allow network administrators to closely analyze the network. The lightweight access point will send Layer 2 Lightweight Access Point (LWAPP) mode discovery request messages. If the attempt fails, the LAP will try Layer 3 LWAPP WLC discovery
One key measurement for interference is the Signal-to-Noise Ratio (SNR). This calculation measures the WLAN signal as compared to the other undesired signals (noise) in the same space. The higher the SNR, the better the WLAN devices can send data successfully.
A WLAN client that is operating in half-duplex mode will delay all clients in that WLAN.
Process order that the client and access point goes through to create a connection: probe request/response, authentication request/response, association request/response
