802.11 Wireless Network Overview

Wireless networks using the 802.11b and 802.11g standards have become extremely popular since their introduction. This article some basic information about wireless networks, their security and a glossary of the common terms.

Basic Security

Each wireless network should have some form of security to prevent unwanted intrusions, at the very least this means enabling Wired Equivalent Privacy (WEP) on the access point. This was the security standard that was first adopted when 802.11 was released but it has many flaws that enable it to be cracked rather easily. It can use 64 bit and 128 bit keys, represented by a string of Hex characters.

WEP was replaced by Wi-Fi Protected Access (WPA) and WPA2 with the release of the 802.11g standard. There are two methods of using WPA, the more secure option of using an authentication server to distribute different keys to the users of the network or the less secure but easier to deal with method of using a single pre shared key (PSK) for all the users. When using WPA+PSK a passphrase is entered on the access point and this same phrase must be used on the client when trying to connect to the network.

Some other security ideas;

These methods are best used in conjunction with proper security settings like WPA rather than as standalone methods.

Channels

There are a total of 14 available channel to 802.11b/g networks, some of which may restricted depending on the regulatory body for each country. The channels are on the 2.4 GHz band, starting with channel 1 at 2.412 GHz and finishing with channel 14 at 2.484 GHz. Due to the nature of wireless signals this leads to some overlap between each channel but there are 3 "non overlapping" channels, 1, 6 and 11. While this doesn't mean there is zero interference between these two channels it does make them the best choices and this is the reason most wireless access points will default to one of these channels.

Country Available channels
Europe 1-13
Spain 10-11
France 10-13
Australia 1-13
United States 1-11
Canada 1-11
Japan 14

Each channel can suffer from interference from other networks on the channel, networks on other close channels and other devices operating in the same 2.4 GHz frequency range (microwaves, cordless phones).

The best idea is to pick a channel with the least amount of networks on it (especially if it is channel 1, 6 or 11). You should also experiment with various channels, even though it may have no wireless networks on it there may be other electronic devices interfering with it's signal.

802.11a channels are on the 5 GHz band, starting at 5.15Ghz and ranging through to 5.825Ghz depending on the regulatory body for each country.

Country Available channels
Europe 36,40,44,48,52,56,60,64, 100,104,108,112,116,120,124,128,132,136,140
United States 36,40,44,48,52,56,60,64,149,153,157,161,165
Japan 7,8,9,11,12,16,34,36,38,40,42,44,46,124,128,132,140,183,184,185,187,188,189,192,196

 

WirelessMon has the option to switch between displaying A and B/G channel distributions on the channel graph, the displayed channels for 802..11a are 36,40,44,48,52,56,60,64,149,153,157,161,165.

Glossary

802.11
802.11 is the WiFi standard set by the IEEE for WLANs. There are different variants of 802.11, the most common being: 802.11b (2.4GHz, max data rate 11Mbit/s), 802.11g.(2.4GHz, max data rate 54Mbit/s) and 802.11a (5Ghz, max data rate 54Mbit/s). 802.11n (5 GHz and/or 2.4 GHz, 74-600Mbits/s) is the next proposed standard and is currently still in draft specification (after 4 years).
AES
Advanced Encryption Standard. Uses key sizes of 128, 192 and 256 bits. Used by WPA2.
ATIM Window
Announcement Traffic Indication Messages are used in ad hoc (independent) 802.11 networks to announce the existence of buffered frames.
Beacon Period
Beacons are packets sent by a wireless router to synchronize wireless devices.
DHCP
Dynamic Host Configuration Protocol. An IETF standard used by network administrators to automatically configure hosts. Hosts needing configuration information may broadcast a request that is responded to by a DHCP server.
Dwell Time
802.11 FH networks hop from channel to channel. The amount of time spent on each channel in the hopping sequence is called the dwell time
Fragmentation Threshold
To improve efficiency data is usually broken down into smaller ‘data packets’ when being transmitted by WiFi. The receiver station then reassembles the fragments into the whole. The Fragmentation Threshold determines the maximum size of the data packets.
Gateway Address
A Gateway Address is the IP address of a network point that acts as an entrance to another network.
GPS
Global Positioning System. It is a method to determine geographical coordinates and local time coordinate on Earth using calibrating signals from a network of 24 satellites.
Hop Pattern
Stations select one of the hopping patterns from the Hop Set.
Hop Set
Several Hopping Patterns are defined by the 802.11 frequency-hopping Physical Layer (PHY).
IEEE
Institute of Electrical and Electronic Engineers. The professional body that has standardized the 802.11 networks.
IP
Internet Protocol
MAC Address
Media Access Control Address. A unique identifier for a piece of hardware on a network. It is usually displayed as a string of 6 hex pairs eg FF:FF:FF:FF:FF:FF.
NDIS
Network Driver Interface Specification is an application programming interface (API) for Network Interface Cards (NICs).
PSK
Pre Shared Key. A single passphrase / key used for authentication with WPA and WPA2.
RTS Threshold
A node wishing to send data initiates the process by sending a Request To Send (RTS) frame. The destination node replies with a Clear To Send (CTS) frame. The RTS Threshold is the point at which the data packet size is too small to initiate the RTS/CTS function.
SSID
Service Set Identifier. A alpha numeric string used to identify a wireless network.
Subnet Mask
Also known as a network mask, it is a bitmask used to tell how many bits in an octet(s) identify the subnetwork, and how many bits provide room for host addresses. Subnet masks are usually represented in the same representation for the addresses themselves; in IPv4, dotted decimal notation, four numbers from 0 to 255 separated by periods, e.g. 255.128.0.0.
TCP/IP
Transmission Control Protocol/Internet Protocol.
Tx Power
Transmit Power.
Wardriving
Wardriving is the practice of searching for WiFi network access points using a car, a WiFi enabled computer (usually a laptop or PDA) and frequently, a GPS device. The object is to detect and log the location of the detected SSIDs. Please Note that the legality of wardriving is under review in many jurisdictions. PassMark does not advocate the practice of wardriving in those jurisdictions where it is considered an illegal act.
WEP
Wired Equivalent Privacy. A basic security protocol that was used to provide some degree of privacy for wireless networks when 802.11b was introduced. It was defeated soon after it's adoption and is not considered a very secure method of protecting a wireless network. It can be used with a 64 bit or 128 bit key.
WiFi
Wireless Fidelity was originally a brand name licensed by the Wi-Fi Alliance to describe the technology of Wireless Local Area Networks (WLAN) based on the IEEE 802.11 specifications. It is now considered a generic term and is no longer protected as a brand.
WPA
Wi-Fi Protected Access. It provides a more secure method of protecting data transmission than WEP.
WPA2
A newer version of the WPA protocol that may not work with older hardware, also known as 802.11i. See WPA.
WLAN
Wireless Local Area Network

 

References and Useful Links

802.11 WikiPedia

IEEE Std 802.11b-1999(R2003)