VPN (Virtual Private Network)
VPN or Virtual Private Network describes a network that includes secure remote access for client computers. It can be explained best by looking at its parts. Virtual describes the fact that the network doesn't need to be physically connected. The Private confirms that the data is encrypted and can only be viewed by a defined group. The last word, Network, means that the users configured for VPN can be connected and share files or information.
For instance, field representatives for a company can work on the "home offices" network over the Internet. This access will have the same look and feel as if they are back at the office physically connected to their network, except the reps are working at the speed of their local modem. The data is sent to and from the reps (or to and from the network) encrypted, so it's extremely difficult for anyone to snoop on confidential information.
IPSEC is one of the best VPN solutions. It connects networks via the Internet using encrypted traffic, so an office in San Francisco can share different files and data with an office in Boston in a secure fashion. IPSEC also allows Windows 2000 or Windows XP client machines, which support IPSEC by default, to connect to Real Time's Linux Firewall.
Another option for VPN is PPTP or Point to Point Tunneling Protocol. PPTP works best connecting Real Time's Firewall Solution with remote client machines running Windows 95/98/ME via encrypted network traffic.