Which protocol is commonly used to secure VPN communications at the IP layer?

• A. TLS
• B. TLSv1.2
• C. SSH
• D. IPsec

Answer: (D)

Securing VPN traffic at the IP layer means protecting the IP packets themselves as they travel across an untrusted network. IPsec is built for this purpose: it operates at the network layer and can authenticate, encrypt, and ensure the integrity of each IP datagram, enabling secure tunnels between endpoints. In VPN use, IPsec often runs in tunnel mode, encapsulating entire IP packets so all traffic between the sites or users is protected regardless of the applications in use.

Protocols like TLS and SSH work at higher layers. TLS protects specific application sessions (for example, HTTPS or mail), not the entire IP stream, and SSH secures remote access and file transfers rather than providing a network-layer VPN. TLS v1.2 is simply a version of TLS and remains a transport-layer security protocol rather than a network-layer VPN mechanism.

So, IPsec is the protocol designed to secure VPN communications at the IP layer.