CompTIA Network+ N10-006 Q487

A technician has deployed a new VPN concentrator. The device needs to authenticate users based on a backend directory service.
Which of the following services could be run on the VPN concentrator to perform this authentication?

A. Kerberos
B. RADIUS
C. GRE
D. IPsec

Correct Answer: B

Explanation/Reference:
https://security.stackexchange.com/questions/130095/what-is-the-difference-between-a-radius-server-and-active-directory