FreeS/WAN is an ideal solution for the overworked, harassed network admin who needs to bring together branch offices, telecommuters, and road warriors from anywhere over the Internet, and it does it all for the price of the hardware, with requirements that are surprisingly low.
S/WAN is short for Secure Wide Area Network. FreeS/WAN is a free Linux implementation of IPsec (IP security) protocols. IPsec is built into IPv6, and is optional for IPv4, the current IP (Internet Protocol) deployment. IPsec provides two levels of protection: encryption and authentication, at the IP level of the network protocol stack. Because IPsec operates at the network layer, it secures nearly any type of Internet traffic.