Data sent across the internet is generally not protected from from prying eyes,but to make the internet connection secure and extend the private network virtual private network(VPN) connect can be use.This private network uses a public network(usually internet) to connect remote sites or or users together.Instead of using a dedicated,real-world connection (such as leased line) a VPN uses 'virtual' connection routed through the internet through the company's private to the remote site or employee.
A well design VPN can greatly benefit a company.For example


Extend geographic connectivity
Improve security
Reduce operational costs versus traditional WAN
Improve productivity
Simplify network topology
Provide global networking opportunities
Provide telecomputer support
Provide broadband networking compatibility
Provide faster ROI(return of investment)than traditional WAN

There are two common type of VPN

1.Remote-Access VPN -- Remote access also called a virtual private dial-up network (VPDN), is a user to LAN connection used by company that has employee who need to connect to the private network from various remote locations.Typically, a corporation that wishes to set up a large remote access VPN will out source to an enterprise service provider(ESP).The ESP sets up a network access server(NAS) and provides remote user with desktop client software for there computers.The telecomputer can then dial a toll-free number to reach the NAS and use their VPN client software to access the corporate network.

2.Site-to-Site VPN--Through the use of dedicated equipment and large scale encryption, a company can connect multiple fixed sites over a public network (such as internet).Site to Site VPN can be two types
  • Intranet based-- If a company has one or more remote locations that the use to join single private network, they can create an intranet VPN to connect LAN -to- LAN.
  • Extranet based--When company has close relationship with another company (for example a partner,supplier) they can build an extranet VPN that connects LAN -to- LAN and allows the all various companies to work in a share environment.