Concepts of Basic WLAN Services
Station (STA): a terminal that supports 802.11 standards, such as a PC that has a wireless NIC or a mobile phone that supports WLAN.
Radio signal: high-frequency electromagnetic wave that has long-distance transmission capabilities. Radio signals provide transmission media for 802.11-compliant WLANs. Radio signals described in this document are electromagnetic waves in 2.4 GHz or 5 GHz frequency band.
Access point (AP): a device that provides 802.11-compliant wireless access for STAs to connect wired networks and wireless networks.
- Fat AP: provides wireless access for STAs in the autonomous architecture. A Fat AP provides wireless connection, security, and management functions.
- Virtual access point (VAP): a WLAN service entity on an AP. You can create different VAPs on an AP to provide wireless access service for different user groups.
Service set identifier (SSID): a unique identifier that identifies a wireless network. When you search for available wireless networks on your laptop, SSIDs are displayed to identify the available wireless networks.
SSIDs are classified into two types:- Basic service set identifier (BSSID): a link-layer MAC address of a VAP on an AP. Figure 2-1 shows the relationship between VAP and BSSID.
- Extended service set identifier (ESSID): an identifier of one or a group of wireless networks. For example, in Figure 2-1, SSID guest identifies a wireless network, and SSID internal identifies another wireless network. A STA scans all wireless networks and selects a wireless network based on the SSID. Generally, an SSID refers to an ESSID.
Basic service set (BSS): an area covered by an AP. STAs in a BSS can communicate with each other.
