A Virtual Private Network (VPN) utilises public telecommunications networks to conduct private data communications.  Most VPN implementations use the internet as the public infrastructure and a variety of specialised protocols to support private communications through the internet. VPNs tend to follow a client/server approach whereby VPN clients authenticate users, encrypt data and otherwise manage sessions with VPN servers utilising a technique called tunnelling. The session between two users can only be conducted once the tunnel has been opened up between the two users concerned.

VPN Clients and Servers are typically used in the following three scenarios-

• To support remote access to an intranet
• To support connections between multiple intranets within the same organisation
• To join networks between two organisations, forming an extranet

The main benefit of a VPN is the lower cost needed to support this technology compared to alternatives like traditional leased lines or remote access servers. VPN users typically interact with simple graphical client programs. These applications support creating tunnels, setting configuration parameters, and connecting to and disconnecting from the VPN server. VPN solutions utilize several different network protocols including PPTP, L2TP, IPsec, and SOCKS.  VPN servers can also connect directly to other VPN servers. A VPN server-to-server connection extends the intranet or extranet to span multiple networks.

From an EDI perspective VPN related connections are ideal for smaller size companies who wish to connect to trading partners via a single internet connection.  Many companies have invested in a single internet connection that is used by all of the PCs on a network.  In the case of GXS, VPN software can be installed on a single PC that is connected directly to the internet, or on a PC that is connected to a company network of a network or PCs can be connected via VPN software that is placed on the firewall of the company.  These are illustrated below, connected to GXS Trading Grid Messaging Service.