1-5
Figure 1-4 RADIUS message format
2) The Code field (one byte) decides the type of RADIUS message, as shown in
Table 1-1.
Table 1-1 Description on the major values of the Code field
Code Message type Message description
1 Access-Request
Direction: client->server.
The client transmits this message to the server to determine if
the user can access the network.
This message carries user information. It must contain the
User-Name attribute and may contain the following
attributes: NAS-IP-Address, User-Password and NAS-Port.
2 Access-Accept
Direction: server->client.
The server transmits this message to the client if all the
attribute values carried in the Access-Request message are
acceptable (that is, the user passes the authentication).
3 Access-Reject
Direction: server->client.
The server transmits this message to the client if any attribute
value carried in the Access-Request message is
unacceptable (that is, the user fails the authentication).
4 Accounting-Request
Direction: client->server.
The client transmits this message to the server to request the
server to start or end the accounting (whether to start or to
end the accounting is determined by the Acct-Status-Type
attribute in the message).
This message carries almost the same attributes as those
carried in the Access-Request message.
5 Accounting-Response
Direction: server->client.
The server transmits this message to the client to notify the
client that it has received the Accounting-Request message
and has correctly recorded the accounting information.
3) The Identifier field (one byte) is used to match requests and responses. It changes whenever the
content of the Attributes field changes, and whenever a valid response has been received for a
previous request, but remains unchanged for message retransmission.
4) The Length field (two bytes) specifies the total length of the message (including the Code, Identifier,
Length, Authenticator and Attributes fields). The bytes beyond the length are regarded as padding
and are ignored upon reception. If a received message is shorter than what the Length field
indicates, it is discarded.
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