D-Link DFL-2500 User Guide - Page 212

20 CHAPTER VPN Basics 20.1 Introduction to VPN Long gone is the time when corporate networks were separate isles of local connectivity. Today, most networks are connected to each other by the Internet. Issues of protecting the local networks from Internet-based crime and intrusion are being solved by firewalls, intrusion detection systems, anti-virus software and other security investments. However, business is increasingly often being done across the Internet as a means of efficient and inexpensive communication. As we all have learned the hard way, not all parts of the Internet can be trusted in our time. Private interests as well as corporate communication requirements necessitate a means for data to be able to travel across the Internet to its intended recipient without allowing anyone else to read or alter it. It is equally important that the recipient can verify that no one is falsifying information, i.e. pretending to be someone else. VPNs, Virtual Private Networks, provide a very cost efficient means of establishing secure links to parties that wish to exchange information in a trustworthy manner. 20.1.1 VPNs vs Fixed Connections Using leased lines or other non-public channels to exchange data between organizations is not a new concept. It has been done since the first 193