Appendix A WiMAX Security
User’s Guide
258
RADIUS
RADIUS is based on a client-server model that supports authentication,
authorization and accounting. The base station is the client and the server is the
RADIUS server. The RADIUS server handles the following tasks:
• Authentication
Determines the identity of the users.
• Authorization
Determines the network services available to authenticated users once they are
connected to the network.
•Accounting
Keeps track of the client’s network activity.
RADIUS is a simple package exchange in which your base station acts as a
message relay between the MS/SS and the network RADIUS server.

Types of RADIUS Messages

The following types of RADIUS messages are exchanged between the base station
and the RADIUS server for user authentication:
• Access-Request
Sent by an base station requesting authentication.
• Access-Reject
Sent by a RADIUS server rejecting access.
• Access-Accept
Sent by a RADIUS server allowing access.
• Access-Challenge
Sent by a RADIUS server requesting more information in order to allow access.
The base station sends a proper response from the user and then sends another
Access-Request message.
The following types of RADIUS messages are exchanged between the base station
and the RADIUS server for user accounting:
•Accounting-Request
Sent by the base station requesting accounting.
• Accounting-Response
Sent by the RADIUS server to indicate that it has started or stopped accounting.
In order to ensure network security, the access point and the RADIUS server use a
shared secret key, which is a password they both know. The key is not sent over