WLAN: Technical principles

In principle, wireless networks can be operated in one of two ways. In ad-hoc mode, two or more mobile end devices are connected to one another directly. For this to work, every device involved must be equipped with a wireless LAN--Local Area Network card. In most cases, however, WLANs are operated in infrastructure mode. With this method, the devices concerned communicate with each other through an access point, which acts as a central wireless link. This type of access point also facilitates connections to wired sections of the network.

The most well-known example of an access point is the wireless DSL router. The Institute of Electrical and Electronics Engineers (IEEE) defines standards for wireless data transmission, which is why they are called IEEE 802.11x. An alternative to WLAN that is not as widespread is WIMAX (Worldwide Interoperability for Microwave Access), which is based on the IEEE 802.16 standard.

WLAN: Security mechanisms

Several encryption methods were developed to protect data traffic in WLANs. WEP encryption should not be used any more, as it does not provide adequate protection. WPA is the minimum level of protection required. WPA stands for Wi-Fi Protected Access - this method was standardised by the Wi-Fi Alliance, a network of companies working in the WLAN industry.

To protect WLANs effectively, however, it is best to use the further developed version WPA2 in conjunction with a password called a pre-shared key (PSK) ('WPA2-PSK'). This pre-shared key must be known to all WLAN subscribers. It serves to generate a special session key every time there is a new login. However, this key only protects against intruders if the passwords used are long and complex enough.

LAN: How it works

Unlike in a wireless LAN, in a conventional local area network the individual computers are connected to one another and to the Internet via cables, which usually run from the computers to a switch or router. This switch or router then manages the network like a server, which receives requests and commands from the various computers (or 'clients').

The switch or router distributes IP addresses throughout the network to do this: IP (Internet Protocol) addresses provide a means of locating individual computers in the network. An LAN can incorporate other devices, such as printers, as well as standard computers. Routers often feature a built-in DSL modem that governs the connection to the Internet, so only one device is needed.

IP addresses have to be assigned because, whereas electric current can be easily distributed to several devices via a multi-way socket for example, a network connection does not work like that. A computer, or a printer for that matter, must be registered with the network and must be assigned a unique network address (IP address).

So you cannot just turn one connection into two, then expect both devices to be connected to the network and capable of exchanging data with one another.