TCP/IP Tutorial and Technical Overview - IBM Redbooks

Request and response type Value
TLS 13
TTLS 21
PEAP 25
MS-CHAP-V2 29
In Figure 23-11, the Type field in the EAPOL header (802.1x authentication) is 0,
indicating that it is an EAP packet. In the EAP header, a value of 2 for the Code
field indicates that it is a response packet. A value of 1 for the Type field indicates
an Identity packet. All these values clearly give us an idea that it is an
EAP-Response/Identity packet.
Figure 23-11 EAP-Response and Identity packet
Figure 23-12 shows a EAP-Nak packet. This packet is sent only as an EAP
response to indicate that the authentication type sent in the Request packet is
unacceptable to the peer. The value of the Type field in the EAP header is 3 to
indicate that it is an EAP-Nak packet.
Figure 23-12 EAP Nak
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