3Com 2928 User Guide - Page 400

8) The RADIUS server returns a stop-accounting response (Accounting-Response) and stops accounting for the user. 9) The user stops access to network resources. RADIUS Packet Format RADIUS uses UDP to transmit messages. It ensures the smooth message exchange between the RADIUS server and the client through a series of mechanisms, including the timer management mechanism, retransmission mechanism, and slave server mechanism. Figure 1-3 shows the RADIUS packet format. Figure 1-3 RADIUS packet format Descriptions of the fields are as follows: 1) The Code field (1-byte long) is for indicating the type of the RADIUS packet. Table 1-1 gives the possible values and their meanings. Table 1-1 Main values of the Code field Code 1 2 3 4 5 Packet type Access-Request Access-Accept Access-Reject Accounting-Request Accounting-Response Description From the client to the server. A packet of this type carries user information for the server to authenticate the user. It must contain the User-Name attribute and can optionally contain the attributes of NAS-IP-Address, User-Password, and NAS-Port. From the server to the client. If all the attribute values carried in the Access-Request are acceptable, that is, the authentication succeeds, the server sends an Access-Accept response. From the server to the client. If any attribute value carried in the Access-Request is unacceptable, the server rejects the user and sends an Access-Reject response. From the client to the server. A packet of this type carries user information for the server to start/stop accounting for the user. It contains the Acct-Status-Type attribute, which indicates whether the server is requested to start the accounting or to end the accounting. From the server to the client. The server sends to the client a packet of this type to notify that it has received the Accounting-Request and has correctly started recording the accounting information. 1-3