3Com 4500 PWR 26-Port Configuration Manual page 349

The Length field indicates the size of an EAP packet, which includes the Code, Identifier, Length,
and Data fields.
The Data field carries the EAP packet, who
A Success or Failure packet does not contain the Data field, so the Length field of it is 4.
Figure 28-5 shows the format of the Data field of a Request packet or a Response packet.
Figure 28-5 The format of the Data field of a Request packet or a Response packet
The Type field indicates the EAP authentication type. A value of 1 i
packet is used to query the identity of the peer. A value of 4 repre
PPP CHAP) and indicates that the packet includes query informati
The Type Date field differs with types of Request and Respon
Newly added fields for EAP authentication
T wo fields, EAP-message and Message-authenticator, are added to a RADIUS protocol packet for EAP
authentication. (Refer to the Introduction to RADIUS protocol section in the AAA Operation for
information about the format of a RADIUS protocol packet.)
The EAP-message field, whose format is shown in
The maximum size of the string field is 253 bytes. EAP packets with their size larger than 253 bytes are
fragmented and are encapsulated in multiple EAP-messa
field is 79.
Figure 28-6 The format of an EAP-message field
The Message-authenticator field, whose format is shown in
unauthorized interception to access requesting packets during authentications using CHAP, EAP, and
so on. A packet with the EAP-message field must also have the Message-authenticator field. Otherwise,
the packet is regarded as invalid and is discarded.
Figure 28-7 The format of an Message-authenticator field
802.1x A uthentication Procedure
A 3Com Switch 4500 series Ethernet switch can authenticate supplicant systems in EAP terminating
mode or EAP relay mode.
se format differs with the Code field.
se packets.
Figure 28-6, is used to encapsulate EAP packets.
ge fields. The type code of the EAP-message
Figure
28-5
ndicates Identity and that the
sents MD5-Challenge (similar to
on.
28-7, is used to prevent