3Com 7757 Configuration Manual page 392

392 C 39: 802.1
HAPTER X
C
ONFIGURATION
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 packets.
04: Indicates that the packet is an EAPoL-encapsulated-ASF-Alert packet,
which is used to support the alerting messages of ASF (alerting standards
forum).
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.
The format of an EAP packet
For an EAPoL packet with the Type value being EAP-packet, the corresponding
Packet body is an EAP packet. Its format is illustrated in Figure 91.
Figure 91 The format of an EAP packet
0
Code
In an EAP packet:
The Code field specifies the EAP packet type, which can be Request, Response,
■
Success, or Failure.
The Identifier field is used to match a Response packets with the corresponding
■
Request packet.
The Length field indicates the size of an EAP packet, which includes the Code,
■
Identifier, Length, and Data fields.
The Data field differs with the Code field.
■
A Success or Failure packet does not contain the Data field, so has the Length field
of 4.
Figure 92 shows the Data field of Request and Response type packet.
7 15
Identifier
Length
Data
2
4
N