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
• Channels
• Glossary
• References and Useful Links

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;

• Turn of SSID broadcasting of the access point. This can prevent people trying to connect to your network as they don't know the SSID required. It is not a good idea to turn off SSID broadcasting and leave your access point open (no WEP or WPA) as packet snooping software can be used to determine the SSID from data sent between the access point and any connected clients.
  
  
• MAC address filtering of clients that can connect to the access point. Many access points have the ability to create a list of authorized MAC addresses and will reject any other network cards that try to connect. Like the point above it is not a very thorough security method as authorized MAC addresses can be determine from examining the network traffic between access point and connected clients. MAC addresses of hardware can also be "spoofed", where MAC address of a network can be changed to any value using software.

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.

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.

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

References and Useful Links

802.11 WikiPedia

IEEE Std 802.11b-1999(R2003)