1-6Code Message type Message description4 Accounting-RequestDirection: client->server.The client transmits this message to the server to request the serverto start or end the accounting (whether to start or to end theaccounting is determined by the Acct-Status-Type attribute in themessage).This message carries almost the same attributes as those carried inthe Access-Request message.5 Accounting-ResponseDirection: server->client.The server transmits this message to the client to notify the clientthat it has received the Accounting-Request message and hascorrectly recorded the accounting information.3) 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.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 paddingand are ignored upon reception. If a received message is shorter than what the Length fieldindicates, it is discarded.5) The Authenticator field (16 bytes) is used to authenticate the response from the RADIUS server;and is used in the password hiding algorithm. There are two kinds of authenticators: RequestAuthenticator and Response Authenticator.6) The Attributes field contains specific authentication/authorization/accounting information toprovide the configuration details of a request or response message. This field contains a list of fieldtriplet (Type, Length and Value):z The Type field (one byte) specifies the type of an attribute. Its value ranges from 1 to 255. Table1-2 lists the attributes that are commonly used in RADIUS authentication/authorization.z The Length field (one byte) specifies the total length of the attribute in bytes (including the Type,Length and Value fields).z The Value field (up to 253 bytes) contains the information of the attribute. Its format is determinedby the Type and Length fields.Table 1-2 RADIUS attributesType field value Attribute type Type fieldvalue Attribute type1 User-Name 23 Framed-IPX-Network2 User-Password 24 State3 CHAP-Password 25 Class4 NAS-IP-Address 26 Vendor-Specific5 NAS-Port 27 Session-Timeout6 Service-Type 28 Idle-Timeout7 Framed-Protocol 29 Termination-Action8 Framed-IP-Address 30 Called-Station-Id9 Framed-IP-Netmask 31 Calling-Station-Id
