1-4EAP packet formatAn EAP-Packet-type EAPOL frame carries an EAP packet in its Packet body field. The format of theEAP packet is shown in Figure 1-4.Figure 1-4 EAP packet formatCode: 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 Typefield indicates the EAP authentication type. A value of 1 represents Identity, indicating that thepacket is for querying the identity of the client. A value of 4 represents MD5-Challenge, which aresimilar to the PPP CHAP protocol.Figure 1-5 Format of the Data field in an EAP request/response packetIdentifier: 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 RADIUSTwo attributes of RADIUS are intended for supporting EAP authentication: EAP-Message andMessage-Authenticator. For information about RADIUS packet format, refer to RADIUS Configuration.EAP-MessageThe EAP-Message attribute is used to encapsulate EAP packets. Figure 1-6 shows its encapsulationformat. The value of the Type field is 79. The String field can be up to 253 bytes long. If the EAP packetis longer than 253 bytes, it can be fragmented and encapsulated into multiple EAP-Message attributes.Figure 1-6 Encapsulation format of the EAP-Message attribute0 15Type String7LengthNEAP packets
