Which of the following is a VPN protocol mentioned in the secure network protocols?

• A. WEP
• B. SIP
• C. HTTPS
• D. IPSec

Answer: (D)

VPNs secure IP traffic by tunneling and protecting packets across untrusted networks, and IPSec is a foundational protocol for this purpose. It operates at the IP layer and can create encrypted tunnels (tunnel mode) that wrap whole IP packets between endpoints, enabling both remote-access and site-to-site VPNs. IPSec provides confidentiality, integrity, and authentication, with ESP handling encryption and integrity, and AH offering authentication and integrity (without encryption). This makes IPSec well-suited for protecting all traffic between networks or hosts, which is exactly what VPNs require.

WEP is an old wireless encryption method for protecting 802.11 frames and does not create VPN tunnels. SIP is a signaling protocol used to establish, modify, and terminate multimedia sessions, not to secure IP traffic. HTTPS is HTTP over TLS/SSL, securing web traffic at the application layer rather than providing a VPN tunnel for all IP traffic.