Virtual Private Network (VPN) technology is a popular way of using a public telecommunication network infrastructure (like the worldwide Internet) to interconnect private & remote networks and to provide secure (remote) access to offices or networks. This can be done by using various tunneling protocols and by encrypting, decrypting and authenticating traffic. It provides more or less the same capabilities as (e.g.) a leased line but at a lower cost.
Today, VPN technology is often related with the word “IPSEC” or IP Security which is an industrial standard for establishing VPN communications on the network layer. IPSEC is often considered to be a technology that has a relatively steep learning curve for new users and might not be so easy to setup and maintain in all situations (e.g. filtered networks, networks that deal with some kind of Network Address Translation or NAT).
This document is in PDF format. To view it click here.