IPsec operates at the ________ layer.

• A. Data link
• B. Internet
• C. Transport
• D. Application

Answer: (B)

IPsec secures IP communications by protecting IP packets at the Internet layer of the TCP/IP model. It works directly on the IP packets themselves, providing encryption and/or authentication (via ESP and AH) so that the data remains confidential and integrity-protected as packets travel between hosts or gateways. Because it protects the IP payload regardless of what transport protocol is used (TCP, UDP, etc.), its role sits at the Internet layer rather than the data-link, transport, or application layers. It can operate in transport mode (protecting the payload) or tunnel mode (protecting the entire IP packet by encapsulating it in a new IP packet). Data-link security secures a single link hop, which is not the scope of IPsec, and application-layer security (like TLS) operates at higher layers, not on IP packets themselves.