How WLAN Clients Connect to Access Points – Understanding the Authentication and Association Process

In this lesson, I’ll explain the steps involved when a client device connects to a WLAN after locating an access point (AP). Once the client has identified the AP through active or passive scanning, it begins a series of steps to establish a secure connection. This process involves exchanging several messages or frames to ensure the client is properly authenticated and associated with the WLAN. We’ll go through the stages of this connection process, with a focus on both open system authentication and IEEE 802.1X authentication, often used in enterprise networks.

Overview of WLAN Connection Process

After a client has located an AP, either through active or passive scanning, it will attempt to establish a connection. This involves moving through a series of stages to ensure that the connection is secure and that the client is authorized to access the network. Each step varies slightly depending on whether 802.1X authentication is used, a standard often implemented in enterprise networks to enhance security.

The connection process generally includes three main stages: unauthenticated and unassociated, authenticated but unassociated, and finally authenticated and associated. If 802.1X authentication is used, there is an additional step for establishing encryption between the client and the access point.

Step 1: Unauthenticated and Unassociated

When the client device initially attempts to connect to the WLAN, it starts in the unauthenticated and unassociated state. At this stage, the client has no established connection with the AP, meaning no credentials have been exchanged, and no session has been initiated. In simple terms, the client is “aware” of the AP’s existence but has not yet begun the connection process.

In this stage, the client has detected the AP’s signal but is not yet connected. This status allows the client to initiate communication with the AP, beginning the connection process through a series of frame exchanges.