In this era of globalization, companies are now introducing world wide services. They not only deal with local and regional services, but with international services. What these companies need, in order to render their services properly, is a way to maintain reliable, fast, and secure communication among their offices no matter where it is located.
A solution to this is WAN or wide area network by which a company is able to expand its private network beyond its immediate geographical region by using leased lines such as ISDN (integrated digital network) or OC3 (optical carrier-3). The problem of WAN is its cost. WAN is quite expensive and the cost usually increases with the increasing distance among the offices. As an alternative to WAN, companies are now using a recent technology called VPN, or virtual private network. VPN is basically a private network which exploits internet or another public network instead of the leased lines. By using a virtual connection, VPN connects the distant employee to the company’s private network. By using virtual private network colleagues around the world can work together.
There are some certain features including security, scalability, reliability, network management, and policy management which are needed to be well-designed in a VPN. Mainly, there are two types of virtual private networks. One is virtual private dial-up network, which is also called remote access. It is a user-to-LAN connection used by a company to connect the remote employees to the company’s private network. The companies who need a larger network use ESP, or enterprise service provider. ESP provides the distant clients with desktop user software for their computers and builds up network access servers, or NAS. Suppose a company has hundreds of sales people around the world who need to communicate with the company’s private network for sales purpose, they can use ESP for remote access. Another type of VPN is site-to-site VPN, which can be of two types: Internet-based & External-based. Virtual private networks give the opportunity of encrypted and secure connections between the distant users and the company’s private network by means of a third-party service provider.