Figure 45.3: the Format of EAPOL Data Packet
PAE Ethernet Type: Represents the type of the protocol whose value is 0x888E.
Protocol Version: Represents the version of the protocol supported by the sender of EAPOL
data packets.
Type: represents the type of the EAPOL data packets, including:
• EAP-Packet (whose value is 0x00): the authentication information frame, used to carry EAP
messages. This kind of frame can pass through the authenticator system to transmit EAP
messages between the supplicant system and the authentication server system.
• EAPOL-Start (whose value is 0x01): the frame to start authentication.
• EAPOL-Logoff (whose value is 0x02): the frame requesting to quit.
• EAPOL-Key (whose value is 0x03): the key information frame.
• EAPOL-Encapsulated-ASF-Alert (whose value is 0x04): used to support the Alerting mes-
sages of ASF (Alert Standard Forum). This kind of frame is used to encapsulate the relative
information of network management such as all kinds of alerting information, terminated by
terminal devices.
Length: represents the length of the data, that is, the length of the 'Packet Body', in byte.
There will be no following data domain when its value is 0.
Packet Body: represents the content of the data, which will be in different formats according
to different types.
2. The Format of EAP Data Packets
When the value of Type domain in EAPOL packet is EAP-Packet, the Packet Body is in EAP
format (illustrated in the next figure).
Code: specifies the type of the EAP packet. There are four of them in total: Request (1),
Response (2), Success (3), Failure (4).
• There is no Data domain in the packets of which the type is Success or Failure, and the value
of the Length domains in such packets is 4.
• The format of Data domains in the packets of which the type is Request and Response is
illustrated in the next figure. Type is the authentication type of EAP, the content of Type data
depends on the type. For example, when the value of the type is 1, it means Identity, and is
used to query the identity of the other side. When the type is 4, it means MD5-Challenge,
like PPP CHAP protocol, contains query messages.
308
To Next Page
Loading...
General