Question

____ is suitable for what are called "high-volume service control applications" such as dial-in access to a corporate network.

Answer 1

Answer: a. RADIUS

Explanation:

RADIUS as developed with the idea of allowing its users or clients to be able to authenticate to a dial-in access server. So basically it is a client server protocol and he client here is the firebox and the server is the RADIUS server.  

The authentication mechanism start by user who sends a message to the RADIUS server. Then the RADIUS server upon receiving the message accept or denies it. It accepts if the client is configured to the server.

A large amount of additional information can be sent by the RADIUS server in its Access-Accept messages with users so we can say that RADIUS is uitable for what are called "high-volume service control applications" such as dial-in access to a corporate network.