Exam JN0-451 Topic 11 Question 47 Discussion

According to Wikipedia1, 802.1X is an IEEE Standard for port-based network access control (PNAC). It provides an authentication mechanism to devices wishing to attach to a LAN or WLAN using Extensible Authentication Protocol (EAP) over wired IEEE 802 networks and over 802.11 wireless networks, which is known as "EAP over LAN" or EAPOL.
The authentication process involves three parties: a supplicant (the client device), an authenticator (the network device such as an access point), and an authentication server (typically a RADIUS server). The supplicant must provide valid credentials to the authenticator before it can access the network resources.
The credentials are exchanged with a RADIUS server prior to the 4-way Handshake because the 4-way Handshake is used to establish encryption keys between the supplicant and authenticator after successful authentication2. The credentials are exchanged with a RADIUS server after the 802.11 Association because the 802.11 Association is used to establish a logical link between the supplicant and authenticator before authentication can take place3.