Which of the following is the best way to securely access a network appliance from an external location?

Remote Desktop Protocol (RDP) is primarily used for graphical remote desktop access to Windows machines. While it can be secured with encryption, it is not as universally applicable as SSH for command-line access across various operating systems and devices. Additionally, RDP can be more vulnerable if not properly configured.

Telnet is an older protocol used for text-based communication over the internet. However, it transmits data in plaintext, making it highly insecure for accessing network appliances, especially over public networks. This lack of encryption exposes sensitive information to interception and eavesdropping.

FTPS (File Transfer Protocol Secure) is used for secure file transfers over the network. While it provides encryption for data in transit, it is not designed for remote management or command-line access to network appliances. Its primary function is to ensure secure file transfers rather than access control.