StrongSwan is direct descendant of the discontinued FreeS/WAN project.
As an IPsec based VPN solution which is focused on security and ease of
use, it fully implements the IKEv1/IKEv2 protocols, MOBIKE, NAT-Traversal
via UDP encapsulation (incl. port floating) and Dead Peer Detection. It
also fully supports the Linux 2.6 IPsec stack, IPv6, certificates/keys on
Smartcards and virtual IP address pools.