5.3 Explain methods of user authentication.

5.3 Explain methods of user authentication.
 * PKI
 * Kerberos
 * AAA (RADIUS, TACACS+)
 * Network access control (802.1x, posture assessment)
 * CHAP
 * MS-CHAP
 * EAP
 * Two-factor authentication
 * Multifactor authentication
 * Single sign-on