Which protocol is most commonly used for secure remote terminal connections?

The most commonly used protocol for secure remote terminal connections is SSH, which stands for Secure Shell. SSH provides a secure channel over an unsecured network by using strong encryption methods. This ensures that any data transmitted between the client and the server is protected from eavesdropping and tampering.

SSH is widely preferred for remote management of servers and network devices because it not only allows for secure logins but also supports secure file transfers and tunneling of other protocols. Its robustness and versatility make it the standard choice for system administrators when accessing servers remotely.

In contrast, HTTP is not secure, as it transmits data in plaintext, which can be intercepted easily. DTP, or Dynamic Trunking Protocol, is mainly used in networking for managing VLANs and has no role in secure remote access. SFTP, while it supports secure file transfers, is not primarily used for terminal access; it operates on top of SSH to provide secure file transfer capabilities. Thus, SSH's focus on secure terminal connections solidifies its status as the correct answer.