At which layer does the IPSec protocol operate to encrypt and protect communications between two parties?

IPSec (Internet Protocol Security) operates at the Network layer (Layer 3) of the OSI model, providing security services like authentication and encryption to IP packets. It works directly with IP traffic, protecting entire IP datagrams or IP payloads, which is why it is integral to Virtual Private Networks (VPNs).

The Application layer (Layer 7) is where applications interact with the network, far above where IPSec operates to secure underlying IP communications.

The Transport layer (Layer 4) handles end-to-end communication and data segmentation (e.g., TCP, UDP), but IPSec functions below this layer to secure the IP packets themselves.

The Data link layer (Layer 2) is responsible for local network communication and MAC addressing, which is below the scope of IPSec, an IP-level protocol.