3Com 2928 User Guide - Page 359

EAP packet format An EAP-Packet-type EAPOL frame carries an EAP packet in its Packet body field. The format of the EAP packet is shown in Figure 1-4. Figure 1-4 EAP packet format Code: Type of the EAP packet, which can be Request, Response, Success, or Failure. z An EAP success/failure packet has no Data field, and has a length of 4. z An EAP Request/Response packet has a Data field in the format shown in Figure 1-5. The Type field indicates the EAP authentication type. A value of 1 represents Identity, indicating that the packet is for querying the identity of the client. A value of 4 represents MD5-Challenge, which are similar to the PPP CHAP protocol. Figure 1-5 Format of the Data field in an EAP request/response packet Identifier: Helps match responses with requests. Length: Length of the EAP packet, including the Code, Identifier, Length, and Data fields, in bytes. Data: Content of the EAP packet. Its format is determined by the Code field. EAP over RADIUS Two attributes of RADIUS are intended for supporting EAP authentication: EAP-Message and Message-Authenticator. For information about RADIUS packet format, refer to RADIUS Configuration. EAP-Message The EAP-Message attribute is used to encapsulate EAP packets. Figure 1-6 shows its encapsulation format. The value of the Type field is 79. The String field can be up to 253 bytes long. If the EAP packet is longer than 253 bytes, it can be fragmented and encapsulated into multiple EAP-Message attributes. Figure 1-6 Encapsulation format of the EAP-Message attribute 0 7 Type 15 Length N String EAP packets 1-4