A virtual private network (VPN) is a network that uses a public telecommunication infrastructure, such as the Internet, to provide remote offices or individual users with secure access to their organization's network. A virtual private network can be contrasted with an expensive system of owned or leased lines that can only be used by one organization. The goal of a VPN is to provide the organization with the same capabilities, but at a much lower cost.
What Makes a VPN?
A well-designed VPN can greatly benefit a company. For example, it can:

* Extend geographic connectivity
* Improve security
* Reduce operational costs versus traditional WAN
* Reduce transit time and transportation costs for remote users
* Improve productivity
* Simplify network topology
* Provide global networking opportunities
* Provide telecommuter support
* Provide broadband networking compatibility
* Provide faster ROI (return on investment) than traditional WAN

What features are needed in a well-designed VPN? It should incorporate:

* Security
* Reliability
* Scalability
* Network management
* Policy management
A typical VPN might have a main LAN at the corporate headquarters of a company, other LANs at remote offices or facilities and individual users connecting from out in the field. VPN solutions support remote access and private data communications over public networks as a cheaper alternative to leased lines. VPN clients communicate with VPN servers utilizing a number of specialized protocols.