Which of the following is a common Windows authentication protocol used by the IEEE 802.1X security standard?

A.
TACACS

B.
LDAP

C.
RADIUS

D.
SSL/TLS

Explanation:
Remote Authentication Dial In User Service (RADIUS) is a networking protocol that provides centralized access, authorization and accounting management for people or computers to connect and use a network service. When a person or device connects to a network often authentication is required. RADIUS is commonly used by ISPs andcorporations managing access to the Internet or internal networks employing a variety of networking technologies, including modems, DSL, wireless and VPNs. It is a common Windows authentication protocol used by the IEEE 802.1X security standard. Answer option A is incorrect. Terminal Access Controller Access-Control System (TACACS) is a remote authentication protocol that is used to communicate with an authentication server commonly used in UNIX networks. TACACS allows a remote access server to communicate with an authentication server in order to determine if the user has access to the network. TACACS allows a client to accept a username and password and send a query to a TACACS authentication server, sometimes called a TACACS daemon. It uses UDP port 49 as the default port. Answer option B is incorrect. Lightweight Directory Access Protocol (LDAP) is a protocol used to query and modify information stored within directory services. Answer option D is incorrect. The Secure Sockets Layer (SSL) and the Transport Layer Security (TLS) protocols are used to provide transport level security for Web services applications.