Encapsulation Of Eapol Messages - H3C S5100-SI Operation Manual

Encapsulation of EAPoL Messages

The format of an EAPoL packet
EAPoL is a packet encapsulation format defined in 802.1x. To enable EAP protocol packets
to be transmitted between supplicant systems and authenticator systems through LANs,
EAP protocol packets are encapsulated in EAPoL format. The following figure illustrates
the structure of an EAPoL packet.
Figure 1-3 The format of an EAPoL packet
In an EAPoL packet:
The PAE Ethernet type field holds the protocol identifier. The identifier for 802.1x is
0x888E.
The Protocol version field holds the version of the protocol supported by the sender of
the EAPoL packet.
The Type field can be one of the following:
00: Indicates that the packet is an EAP-packet, which carries authentication
information.
01: Indicates that the packet is an EAPoL-start packet, which initiates the
authentication.
02: Indicates that the packet is an EAPoL-logoff packet, which sends logging off
requests.
03: Indicates that the packet is an EAPoL-key packet, which carries key
information.
04: Indicates that the packet is an EAPoL-encapsulated-ASF-Alert packet,
which is used to support the alerting messages of Alerting Standards Forum
(ASF).
The Length field indicates the size of the Packet body field. A value of 0 indicates that
the Packet Body field does not exist.
The Packet body field differs with the Type field.
Note that EAPoL-Start, EAPoL-Logoff, and EAPoL-Key packets are only transmitted
between the supplicant system and the authenticator system. EAP packets are
encapsulated by RADIUS protocol to allow them successfully reach the authentication
servers. Network management-related information (such as alarming information) is
encapsulated in EAPoL-Encapsulated-ASF-Alert packets, which are terminated by
authenticator systems.
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