Which of the following protocol was used by the INITIAL version of the Terminal Access Controller Access
Control System TACACS for communication between clients and servers?

A.
TCP

B.
SSL

C.
UDP

D.
SSH

Explanation:
TACACS has been through three generations: TACACS, Extended TACACS (XTACACS), and TACACS+.
TACACS combines its authentication and authorization processes; XTACACS separates authentication,
authorization, and auditing processes; and TACACS+ is XTACACS with extended two-factor user
authentication. TACACS uses fixed passwords for authentication, while TACACS+ allows users to employ
dynamic (one-time) passwords, which provides more protection.
The original TACACS was developed during the days of ARPANET which is the basis for the Internet. TACACS
uses UDP as its communication protocol. TACACS+ uses TCP as its communication protocol.
Incorrect Answers:
A: TACACS uses UDP as its communication protocol, not TCP.
B: TACACS uses UDP as its communication protocol, not SSL.
D: TACACS uses UDP as its communication protocol, not SSH.

Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, p. 234
Jacobs, Josh, et al., SSCP Systems Security Certified Practitioner Study Guide and DVD Training System,
Syngress, Rockland, 2003, p. 450
http://en.wikipedia.org/wiki/TACACS