Medium Access Control (MAC) and Physical Layer (PHY) - CISE

4-June-07 P1901_PRO_016_r0
In IEEE 802.1X an access and authentication dialog is defined for the case of authenticator initiated exchange. This
dialog is formed by the following sequence of messages:
• Message A: Authenticator to Supplicant
o EAPOL with Code field: Request (1) and Type field: Identity (1)
• Message B: Supplicant to Authenticator
o EAPOL with Code field: Response (2) and Type field: Identity (1)
• Message C: Authenticator to Supplicant
o EAPOL with Code field: Request (1) and Type field: Challenge (4)
• Message D: Supplicant to Authenticator
o EAPOL with Code field: Response (2) and Type field: Challenge (4)
• Message E: Authenticator to Supplicant
o EAPOL with Code field: Success (3) or Failure (4)
In IEEE P1901 Message A of the previous dialog should be implemented by the use of the Access Frame described
in section 4.3.8., Message B should be implemented by the use of the Access Reply Frame described in section
4.3.9 and Message E should be implemented by the use of the Access Protocol Packet described in section 9.1.3.
Messages C and D serve for the purpose of authentication. With message C the Authenticator sends a random
challenge of 16 octets to the Supplicant and message D is the response of the Supplicant to this challenge. This
Response is a 16-octet MD5 hash calculated over the random challenge and the secret shared by the Supplicant and
the Authentication Server and other fields [RFC 2865]. This secret should be the Serial Number of the Supplicant.
IEEE 802.1X states that “The EAPOL encapsulation used with IEEE802.3/Ethernet can be applied to other LAN
technologies that share the same basic frame format as Ethernet” as is the case of IEEE P1901 technology. As a
consequence, the format of Messages C and D in IEEE P1901, which follows the rules of EAPOL packets, are
encapsulated in CLPDUs. The formats are the following:
Submission page 287 UPA-OPERA