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Overview 511
Figure 129 RADIUS packet structure
1 The Code field decides the type of the RADIUS packet, as shown in Table 395.
2 The Identifier field (one byte) identifies the request and response packets. It is
subject to the Attribute field and varies with the received valid responses, but
keeps unchanged during retransmission.
3 The Length field (two bytes) specifies the total length of the packet (including the
Code, Identifier, Length, Authenticator and Attribute fields). The bytes beyond the
length will be regarded as padding bytes and are ignored upon receiving the
packet. If the received packet is shorter than the value of this field, it will be
discarded.
Code
Attribute
Identifier
0
7
Length
Authenticator
7 15 31
Table 395 Description on major values of the Code field
Code Packet type Packet description
1 Access-Request Direction: client->server.
The client transmits this packet to the server to determine if the
user can access the network.
This packet 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 packet to the client if all the attribute
values carried in the Access-Request packet are acceptable (that
is, the user passes the authentication).
3 Access-Reject Direction: server->client.
The server transmits this packet to the client if any attribute
value carried in the Access-Request packet is unacceptable (that
is, the user fails the authentication).
4 Accounting-Reques
t
Direction: client->server.
The client transmits this packet 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 packet).
This packet carries almost the same attributes as those carried
in the Access-Request packet.
5 Accounting-Respo
nse
Direction: server->client.
The server transmits this packet to the client to notify the client
that it has received the Accounting-Request packet and has
correctly recorded the accounting information.