On a Windows server the 'Network Policy Service' (NPS) allows you to authenticate users with the RADIUS protocol. This protocol is used by hardware routers to authenticate VPN users and, through Wi-Fi access points, to authenticate Wi-Fi client users.
UserLock can audit, control and restrict Wi-Fi and VPN sessions authenticated through NPS architecture thanks to the UserLock 'NPS agent' specifically designed to be loaded in the 'Network Policy Server' service.
UserLock doesn't deploy this specific agent automatically. It needs to be deployed manually through the console or by file copy.
On Windows Server 2003, the "Network Policy Server" service is called "Internet Authentication Service".