1-5Figure 1-3 RADIUS message format1) 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 fieldCode Message type Message description1 Access-RequestDirection: client->server.The client transmits this message to the server todetermine if the user can access the network.This message carries user information. It must containthe User-Name attribute and may contain the followingattributes: NAS-IP-Address, User-Password andNAS-Port.2 Access-AcceptDirection: server->client.The server transmits this message to the client if all theattribute values carried in the Access-Requestmessage are acceptable (that is, the user passes theauthentication).3 Access-RejectDirection: server->client.The server transmits this message to the client if anyattribute value carried in the Access-Request messageis unacceptable (that is, the user fails theauthentication).4 Accounting-RequestDirection: client->server.The client transmits this message to the server torequest the server to start or end the accounting(whether to start or to end the accounting is determinedby the Acct-Status-Type attribute in the message).This message carries almost the same attributes asthose carried in the Access-Request message.5 Accounting-ResponseDirection: server->client.The server transmits this message to the client to notifythe client that it has received the Accounting-Requestmessage and has correctly recorded the accountinginformation.2) The Identifier field (one byte) is used to match requests and responses. It changes whenever thecontent of the Attributes field changes, and whenever a valid response has been received for aprevious request, but remains unchanged for message retransmission.
