The scenario described involves the use of a RADIUS (Remote Authentication Dial-In User Service) server. RADIUS is a client-server protocol that provides centralized network authentication12. In this case, the access point (client) forwards the connection request to the RADIUS server, which then sends authentication keys to both the access point and the user’s laptop (supplicant). This process helps the access point identify the wireless client12.

RADIUS servers are also known as AAA (Authentication, Authorization, and Accounting) servers because they provide these three services1. The authentication process begins when a user attempts to log into the network. Their device will request access either through the use of credentials or by presenting an X.509 digital certificate1. The RADIUS server then compares the user’s information with a list of users stored in a directory or IDP (Identity Provider)1.

Therefore, the authentication method demonstrated in the scenario is centralized authentication (Option D), where a central server (in this case, the RADIUS server) handles the authentication of users.