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

4-June-07 P1901_PRO_016_r0
Figure 146: Encryption and Integrity process for all but the first packet
The MIC is computed in both cases using CBC-MAC, which encrypts a starting block B0 and then successively
XORs subsequent blocks and encrypts the result. Although the result is a MIC of 128 bits, the lower 96 bits are
discarded, and a final 32-bit MIC is obtained.
Once the MIC has been computed and appended to the plaintext data, the encryption takes place using Counter
Mode (CTR).
10.2 AAA protocol
In section 9.1.3 the access method used in IEEE P1901 has been described. Nevertheless, for the sake of security,
section 9.1.3 is to be complemented with the AAA protocol that is described in the present section.
The access and authentication control system of IEEE P1901 follows closely the one described in IEEE802.1X
which in turn relies on the Extensible Authentication Protocol (EAP) [RFC3748] over LAN (EAPOL). IEEE802.1X
provides the description of EAPOL.
The purpose of IEEE 802.1X is to implement access control at the point at which a user joins the network. In the
process of application of IEEE 802.1X the network entities can take one of three roles: Supplicant, Authenticator
and Authentication Server (AS).
The device asking for connection to the network is known as the Supplicant and in IEEE P1901 can be either a CPE
or a TDR. The Authenticator can be either the HE or a TDR. The Authentication Server will normally be
centralized.
The IEEE 802.1X access control mechanisms apply to the association between a CPE or TDR and a Master.
Submission page 286 UPA-OPERA