RADIUS: IP-Pooling and connection management

I understand that the radius keeps track of all open connections and their assigned IP addresses. If one of these connections closes, the radius can pass on an access-stop message to a CENTRAL CONTROLLER to indicate the end of this one connection. What about the case that the CENTRAL CONTROLLER realizes that another entity of the system is down. Does the CENTRAL CONTROLLER need to send an access-stop to the radius for each of the current open/active connections, or can it send one message to the radius? Will the radius send the required access-stop message to the other entities (IE:NAS) upon reception of this? Thanx. André Ferreira