Final answer:
option a.I recommend TACACS+ for Beatrix's authentication server requirements due to its granular control over device commands and the fact that it encrypts the entire packet which provides enhanced security compared to RADIUS.
Step-by-step explanation:
If Beatrix is looking to implement an authentication server to authenticate network devices and ensure encryption of communications, I recommend using the TACACS+ protocol. TACACS+ stands for Terminal Access Controller Access-Control System Plus, and it provides more granular control over each command that is issued on a device.
Unlike RADIUS, which combines authentication and authorization in a less flexible manner, TACACS+ separates these functionalities to allow more tailored access control. Furthermore, TACACS+ encrypts the entire body of the packet, providing a higher degree of security for authentication and authorization communications over a network compared to RADIUS which only encrypts the password. Therefore, TACACS+ would be an excellent choice for Beatrix's requirements in a professional context for higher security measures.