HP MSR2000 Configuration Manual page 15

RADIUS packet format
RADIUS uses UDP to transmit packets. To ensure smooth packet exchange between the RADIUS server
and the client, RADIUS uses a series of mechanisms, including the timer mechanism, the retransmission
mechanism, and the backup server mechanism.
Figure 4 RADIUS packet format
Descriptions of the fields are as follows:
The Code field (1 byte long) indicates the type of the RADIUS packet.
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and their meanings.
Table 1 Main values of the Code field
Code Packet type
1 Access-Request
2 Access-Accept
3 Access-Reject
4 Accounting-Request
5 Accounting-Response
The Identifier field (1 byte long) is used to match response packets with request packets and to detect
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duplicate request packets. The request and response packets of the same exchange process for the
same purpose (such as authentication or accounting) have the same identifier.
The Length field (2 bytes long) indicates the length of the entire packet (in bytes), including the Code,
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Identifier, Length, Authenticator, and Attributes fields. Bytes beyond this length are considered
padding and are ignored by the receiver. If the length of a received packet is less than this length,
the packet is dropped.
Figure 4
Description
From the client to the server. A packet of this type includes 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 attribute values included in the
Access-Request are acceptable, the authentication succeeds, and the server
sends an Access-Accept response.
From the server to the client. If any attribute value included in the
Access-Request is unacceptable, the authentication fails, and the server sends
an Access-Reject response.
From the client to the server. A packet of this type includes user information
for the server to start or stop accounting for the user. The Acct-Status-Type
attribute in the packet indicates whether to start or stop accounting.
From the server to the client. The server sends a packet of this type to notify
the client that it has received the Accounting-Request and has successfully
recorded the accounting information.
4
shows the RADIUS packet format.
Table 1 gives the main values