Which of the following is an authentication and accounting service that uses TCP for connecting to
routers and switches?

A.
DIAMETER

B.
RADIUS

C.
TACACS+

D.
Kerberos

Explanation:
TACACS+ is an authentication, authorization, and accounting (AAA) service that makes us of TCP only.
Incorrect Answers:
A: DIAMETER makes use of TCP, as well as SCTP.
B: RADIUS makes use of UDP.
D: Kerberos is not an authentication and accounting service, but an authentication protocol.
http://en.wikipedia.org/wiki/TACACS
http://en.wikipedia.org/wiki/Diameter_(protocol)
http://en.wikipedia.org/wiki/RADIUS
http://en.wikipedia.org/wiki/Kerberos_(protocol)