Wifi

Overview

Wireless LANs devices communicate using the WiFi transmission technology which is defined by the IEEE in a specification known as 802.11 and is trademarked by the WiFi Alliance. There have been several generations of the 802.11 standard introduced over the last decade including: 802.11b (11 Mbps), 802.11a (54 Mbps), and 802.11g (also 54 Mbps but offering a further reach than 802.11a). 802.11g is currently the most popular, but soon will be replaced by 802.11n which is currently in the draft stage and will offer speeds up to 540 Mbps.

Wireless devices such as wireless network cards and wireless hubs usually support two wireless modes: AdHoc and Infrastructure. If you simply want two wireless devices to communicate with each other, then both devices should be set to AdHoc mode. If you would like to have multiple wireless devices to be able to access your home or company LAN through a wireless access point (WAP) a.k.a. Access Point (AP), then all of the wireless devices, including the device being used as the access point, should be set to Infrastructure mode. Many businesses like coffee shops, airports, even city malls offer access to their local area networks and the Internet to the public using WAPs. The term used to refer to these publicly accessible WAPs is a wireless "hot spot." In some cases users are charged a fee for access to the network, in other cases they are not, it is typically up to the business providing the service the make that decision.

Wireless Access Points (WAPs) and Service Set Identifier (SSIDs)

When in Infrastructure mode (the default mode), WAPs can be used as access points for other wireless devices to connect to wired LANs. WAPs broadcast SSIDs which are 32 octet (byte) IDs that enable other wireless devices to "see" and thereby establish a connection with the access point which has a wired connection to a LAN switch port. For security reasons some network administrators will disable the broadcasting of an SSID by their WAP devices to prevent unwanted users from being able to detect the access points and attempt to hack into them. A hacker technique known as "war games driving" is sometimes used by unscrupulous people who cruise industrial parks and residential neighborhoods looking for WAPs that they can access and use for devious purposes without detection of where the activity is truly originating from. However, turning off the broadcasting of a WAP's SSID does not prevent the hacker's ability to gain access to the WAP. Anytime a legitimate device connects to the WAP the SSID is transmitted clear text and a hacker can passively "sniff" the wireless network signal and detect the exchange of the SSID between the two devices.

WAP Security

The best way to prevent access to a WAP by unwanted users is to use authentication protocols like RADIUS. Although considered an expensive solution, authentication techniques are commonly used by WiFi hot spots. A simpler more cost effective means of protecting access to a WAP is to secure WAP transmissions. WAP transmissions can be secured by using the less stringent Wireless Encryption Protocol (WEP) which is considered to be weak for most security purposes. Newer second and third generation protocols known as WiFi Protected Access (WPA) versions 1 and 2 are considered very secure when used with strong password protection and are built-in to most of the newer WAPs.

Ad-Hoc Mode

When WAPs are configured for Ad-Hoc mode they can communicate directly with each other and other wireless devices, but cannot bridge to wired LANs. Ad-Hoc mode allows you to build an all-wireless LAN, but performance suffers as the numbers of devices increases, and large ad-hoc networks can quickly become difficult to manage.