3Com 2928 User Guide - Page 401

2) The Identifier field (1-byte long) is for matching request packets and response packets and detecting retransmitted request packets. The request and response packets of the same type have the same identifier. 3) The Length field (2-byte long) indicates the length of the entire packet, including the Code, Identifier, Length, Authenticator, and Attribute fields. The value of the field is in the range 20 to 4096. Bytes beyond the length are considered the padding and are neglected upon reception. If the length of a received packet is less than that indicated by the Length field, the packet is dropped. 4) The Authenticator field (16-byte long) is used to authenticate replies from the RADIUS server, and is also used in the password hiding algorithm. There are two kinds of authenticators: request authenticator and response authenticator. 5) The Attribute field, with a variable length, carries the specific authentication, authorization, and accounting information for defining configuration details of the request or response. This field is represented in triplets of Type, Length, and Value. z Type: One byte, in the range 1 to 255. It indicates the type of the attribute. Commonly used attributes for RADIUS authentication, authorization and accounting are listed in Table 1-2. z Length: One byte for indicating the length of the attribute in bytes, including the Type, Length, and Value fields. z Value: Value of the attribute, up to 253 bytes. Its format and content depend on the Type and Length fields. Table 1-2 RADIUS attributes No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Attribute User-Name User-Password CHAP-Password NAS-IP-Address NAS-Port Service-Type Framed-Protocol Framed-IP-Address Framed-IP-Netmask Framed-Routing Filter-ID Framed-MTU Framed-Compression Login-IP-Host Login-Service Login-TCP-Port (unassigned) Reply_Message Callback-Number Callback-ID No. 45 46 47 48 49 50 51 52 53 54 55 56-59 60 61 62 63 64 65 66 67 Attribute Acct-Authentic Acct-Session-Time Acct-Input-Packets Acct-Output-Packets Acct-Terminate-Cause Acct-Multi-Session-Id Acct-Link-Count Acct-Input-Gigawords Acct-Output-Gigawords (unassigned) Event-Timestamp (unassigned) CHAP-Challenge NAS-Port-Type Port-Limit Login-LAT-Port Tunnel-Type Tunnel-Medium-Type Tunnel-Client-Endpoint Tunnel-Server-Endpoint 1-4