WLAN Association Request and Response Frames Explained

Once the WLAN client devices or mobile stations have identified a compatible WLAN network and authenticated with it, they will attempt to join. This is initiated by sending an association request frame.

Fig-1: WLAN association request frame

Figure 1 illustrates the required fields carried by the WLAN Association request frame. All fields are mandatory and must be in the order shown.

The “Capability information” field indicates the type of network the station wants to join. Before the Access Point (AP) accepts the association request frame, it verifies the following:

• Capability Information
• SSID
• Supported Rates

If all the above fields match the parameters of the WLAN network, the frame will be accepted. The AP also decodes the “Listen Interval” field, which indicates how often the STATION listens to beacon frames to monitor the TIM (Traffic Indication Map) element.

WLAN Association Response Frame

WLAN re-association response frame

WLAN APs respond with association response frames after receiving association request frames from mobile stations that want to join the network. All fields in the response are mandatory. As part of the response, the WLAN AP will assign an Association ID (AID). Different vendors may have different methods for ID assignment.