Which protocols are commonly used to secure a VPN tunnel?

• A. HTTPS and FTP
• B. SSH and SMTP
• C. IPsec and TLS/SSL
• D. POP3 and IMAP

Answer: (C)

VPNs rely on strong encryption and authentication at different layers, so two widely used families are IPsec and TLS/SSL. IPsec protects IP packets between gateways or hosts, operating at the network layer and enabling tunnel mode to create a secure path across untrusted networks; it uses mechanisms like IKE to negotiate keys and establish security associations. TLS/SSL protects the data channel for VPNs that ride above the transport layer, as seen in SSL VPNs where the tunnel is secured with TLS/SSL certificates and encryption and often accessed via a web browser or similar client. Together, these protocols cover the common approaches to securing VPN tunnels. The other protocols mentioned pertain to web, file transfer, mail, or secure remote access but do not, by themselves, define a VPN tunnel in the way IPsec or TLS/SSL do.