Joe, a security administrator, needs to extend the organization's remote access functionality to be used by staff while travelling. Joe needs to maintain separate access control functionalities for…

RADIUS typically combines authentication and authorization into a single process, making it less flexible than TACACS+ for defining separate and granular authorization policies for distinct services.

TACACS+ explicitly separates authentication, authorization, and accounting into distinct processes, allowing an administrator to define different, granular authorization policies for various services (e.g., internal, external, VOIP) even after a user has been authenticated. This distinct separation of authorization is ideal for meeting the requirement of maintaining separate access control functionalities for specific services.

While Diameter is a modern and more robust AAA protocol than RADIUS, it generally does not offer the same distinct separation of authorization from authentication for service-specific granularity as TACACS+.

Kerberos is primarily an authentication protocol that issues tickets for service access and does not inherently provide the comprehensive, separate authorization and accounting functionalities for network access services required for this scenario.