PLANET WGSW-52040 - Manual (Page 360)

 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
messages 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).
Figure 42-4: the Format of EAP Data Packets
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.
Figure 42-5: the Format of Data Domain in Request and Response Packets
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