What family of protocols provides remote authentication in a server environment?

The correct choice is TACACS, which stands for Terminal Access Controller Access-Control System. TACACS provides remote authentication, especially in networked environments such as servers. It allows clients to communicate securely with a centralized server to authenticate users. This protocol is particularly designed to handle authentication, authorization, and accounting (AAA) for users accessing network services and devices. TACACS can offer more granular control compared to some other protocols, making it a preferred choice in many enterprise environments.

While Kerberos is also used for authentication purposes, it operates differently and is typically used within a domain environment where it relies on ticket-based authentication. LDAP, which stands for Lightweight Directory Access Protocol, is used for querying and modifying directory services but does not inherently provide authentication solely on its own. On the other hand, FTP (File Transfer Protocol) is primarily designed for transferring files and does not focus on authentication in a server environment. Hence, TACACS stands out as the most appropriate option for remote authentication within a server context.