1-3
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 Packet type Description
1 Access-Request
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.
2 Access-Accept
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.
3 Access-Reject
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.
4 Accounting-Request
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.
5 Accounting-Response
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.
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