Architecture of WLAN

Stations

All components that can connect into a wireless medium in a network are referred to as stations. All stations are equipped with wireless network interface cards (WNICs). Wireless stations fall into one of two categories: access points and clients.

• Access points

Access points (APs) are base stations for the wireless network. They transmit and receive radio frequencies for wireless enabled devices to communicate with.

• Clients

Wireless clients can be mobile devices such as laptops, personal digital assistants, IP phones, or fixed devices such as desktops and workstations that are equipped with a wireless network interface.

Basic service set

The basic service set (BSS) is a set of all stations that can communicate with each other. There are two types of BSS: independent BSS and infrastructure BSS. Every BSS has an identification (ID) called the BSSID, which is the MAC address of the access point servicing the BSS.

• Independent basic service set

An independent BSS is an ad-hoc network that contains no access points, which means they can not connect to any other basic service set.

• Infrastructure basic service set

An infrastructure BSS can communicate with other stations not in the same basic service set by communicating through access points.

Extended service set

An extended service set (ESS) is a set of connected BSSes. Access points in an ESS are connected by a distribution system. Each ESS has an ID called the SSID which is a 32-byte (maximum) character string. For example, "linksys" is the default SSID for Linksys routers.

Distribution system

A distribution system connects access points in an extended service setup.