SGS-6341-Series User Manual

42.1.3 The Encapsulation of EAPOL Messages
1. The Format of EAPOL Data Packets
EAPOL is a kind of message encapsulation format defined in 802.1x protocol, and is mainly
used to transmit EAP messages between the supplicant system and the authenticator system
in order to allow the transmission of EAP messages through the LAN. In IEEE 802/Ethernet
LAN environment, the format of EAPOL packet is illustrated in the next figure. The beginning of
the EAPOL packet is the Type/Length domain in MAC frames.
Figure 42-3: 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
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).
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User’s Manual of SGS-6341 series