This document describes version 2 of the Internet Key Exchange (IKE)
protocol. IKE is a component of IPsec used for performing mutual
authentication and establishing and maintaining security associations
(SAs).
This version of the IKE specification combines the contents of what
were previously separate documents, including Internet Security
Association and Key Management Protocol (ISAKMP, RFC 2408), IKE
(RFC 2409), the Internet Domain of Interpretation (DOI, RFC 2407),
Network Address Translation (NAT) Traversal, Legacy
authentication, and remote address acquisition.
Version 2 of IKE does not interoperate with version 1, but it has
enough of the header format in common that both versions can
unambiguously run over the same UDP port. [STANDARDS-TRACK]