Which of the following is a client/server protocol designed to allow network access servers to authenticate remote users?

The choice of RADIUS is appropriate because it is specifically designed as a client/server protocol to facilitate the authentication of remote users by network access servers. RADIUS, which stands for Remote Authentication Dial-In User Service, integrates user authentication, authorization, and accounting into a single solution, making it ideal for managing remote access.

When a remote user tries to connect to a network, the access server sends the user's credentials to a RADIUS server. The RADIUS server then verifies these credentials against a user database and sends a response back to the access server to allow or deny access. This makes RADIUS a critical component in environments where secure remote access is necessary, such as VPNs and wireless networks.

The other options do not perform the same function as RADIUS. For instance, SSL (Secure Sockets Layer) is primarily a cryptographic protocol used to secure communications over a computer network. NTLM (NT LAN Manager) is a Microsoft authentication protocol used for network authentication in Windows environments but is not specifically designed for remote user authentication through network access servers. LDAP (Lightweight Directory Access Protocol) is primarily used for directory services to read and modify directory information such as user accounts, rather than directly authenticating remote users.

Therefore, RADIUS stands out