IPsec
RFC 2367: PF_KEY Interface
RFC 2412: The OAKLEY Key Determination Protocol
RFC 3706: A Traffic-Based Method of Detecting Dead Internet Key Exchange (IKE) Peers
RFC 3715: IPsec-Network Address Translation (NAT) Compatibility Requirements
RFC 4621: Design of the IKEv2 Mobility and Multihoming (MOBIKE) Protocol
RFC 4809: Requirements for an IPsec Certificate Management Profile