VIRTUAL PRIVATE NETWORK

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The proliferation of the networked economy has spawned fundamental change in how corporations conduct business. Corporate staff is no longer defined by where they do their jobs as much as how well they perform their job functions. Competitive pressures in many industries have spawned alliances and partnerships among enterprises, requiring separate corporations to act and function as one when facing customers. While such developments have increased productivity and profitability for many corporations, they have also created new demands on the corporate network. A network focused solely on connecting fixed corporate sites is no longer feasible for many companies. Remote users, such as telecommuters or road warriors, and external business partners now require access to enterprise computing resources. The classic wide-area network must be extended to accommodate these users. Consequently, many enterprises are considering virtual private networks (VPNs) to complement their existing classic WAN infrastructure.

There is much hype in the industry currently concerning VPNs, their functionality, and how they fit in the enterprise network architecture. Simply defined, a VPN is an enterprise network deployed on a shared infrastructure employing the same security, management, and throughput policies applied in a private network. VPNs are an alternative WAN infrastructure that replace or augment existing private networks that utilize leased-line or enterprise-owned Frame Relay/ATM networks. VPNs do not inherently change 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. A VPN can utilize the most pervasive transport technologies available today: the public Internet, service provider IP backbones, as well as service provider Frame Relay and ATM networks. The functionality of a VPN, however, is defined primarily by the equipment deployed at the edge of the enterprise network and feature integration across the WAN, not by the WAN transport protocol itself.

VPNs are segmented into three categories: remote access, intranets, and extranets. Remote access VPNs connect telecommuters, mobile users, or even smaller remote offices with minimal traffic to the enterprise WAN and corporate computing resources. An intranet VPN connects fixed locations, branch, and home offices, within an enterprise WAN. An extranet extends limited access of enterprise computing resources to business partners, such as suppliers or customers, enabling access to shared information. Each type of VPN has different security and bandwidth management issues to consider.

Thanks to Cisco Systems for wording.