NIST SP 800-41
NIST SP 800-46
IPsec - An IEEE standard, RFC 2411, protocol that provides security capabilities at the Internet Protocol (IP) layer of communications. IPsec's key management protocol is used to negotiate the secret keys that protect VPN communications, and the level and type of security protections that will characterize the VPN. The most widely used key management protocol is the Internet Key Exchange (IKE) protocol.