OpenBSD


OpenBSD is an operating system based on 4.4BSD

The IPsec stack has been present since 1997 (OpenBSD 2.1):
Written by John Ioannidis, Angelos D. Keromytis and Niels Provos

Very stable and robust implementation

Key management daemons:
IKE (called isakmpd) 
Photuris

Support for hardware cryptography since version 2.7