The VPN as a Secure Environment
One of the most popular approaches to establishing a secure computing and network environment is the virtual private network (VPN). VPNs enable organizations to use Internet transport to connect remote offices and remote users to the main corporate site, thus eliminating expensive dedicated WAN links and modem banks. A growing number of business owners are embracing teleworking for their workers, and for good reasons. Some employers use it to save on office space as a company grows. Others see it as a way to give workers the flexibility to extend their day, communicating with coworkers in time zones around the world. By helping employees avoid a long commute or better manage their personal responsibilities. In a tight job market, many entrepreneurs use telecommuting as a means of recruiting and retaining top talent. Furthermore, with the advent of cost-effective, high-bandwidth technologies like DSL, organizations can use VPNs to reduce their connectivity costs while simultaneously increasing remote connection bandwidth. Businesses that run their VPNs over a shared or public infrastructure enjoy the same security, quality of service (QoS), reliability, and manageability as they do in their own private networks. VPNs allow the end customer to realize the cost advantages of shared network.

Site-to-site VPNs are an alternative WAN infrastructure that are used to connect branch offices, home offices, or business partners' sites to all or portions of a company's network. VPNs do not inherently change private WAN requirements, such as support for multiple protocols, high reliability, and extensive scalability - but instead meet these requirements more cost-effectively and with greater flexibility. VPNs provide a comprehensive feature set to meet diverse networking requirements, including support for routing, multiprotocol, and multicast across the VPN.

The two basic types of VPN services are Access VPNs and Site-to-Site VPNs. The three main applications are for remote access, intranet and extranet connectivity.