IPsec (Internet Protocol Security) is a protocol suite that encrypts and authenticates data packets at the network layer (Layer 3). IPsec operates in two modes: transport mode encrypts only the payload; tunnel mode encrypts the entire packet including headers. Typical use cases include site-to-site VPNs between locations and remote access VPNs for mobile workers. In your ISMS, define which connections must be IPsec-protected and which algorithms are permitted. Remove deprecated algorithms (e.g., DES, MD5) from configurations. Key management via IKE (Internet Key Exchange) should also be documented.