Virtual private networks are point-to-point connections across a private or public network such as the Internet. A VPN client uses special TCP/IP-based protocols, called tunnelling protocols, to make a virtual call to a virtual port on a VPN server. In a typical VPN deployment, a client initiates a virtual point-to-point connection to a remote access server over the Internet. The remote access server answers the call, authenticates the caller, and transfers data between the VPN client and the organization’s private network.
There are two types of VPN connections:
Remote access VPN connections enable users working to home or on the road to access a server on a private network using the infrastructure provided by a public network, such as the Internet. From the user’s perspective, the VPN is a point-to-point connection between the computer (the VPN client) and an organizations server. The exact infrastructure of the shared or public network is irrelevant because it appears logically as if the data is set over a dedicated private link.
Site-to-site VPN connections (also known as router-to-router VPN connections) enable organizations to have routed connections between separate offices or with other organization over a public network while helping to maintain secure communication. A routed VPN connection across the Internet logically operates as a dedicated WAN link. When networks are connected over the internet, as shown in the following figure, a router forwards packets to another router across a VPN connection. To the routers, the VPN connection operates as a data-link layer link.
A site-to-site VPN connection connects two portion of a private network. The VPN server provides a routed connection to the network to which the VPN server is attached. The calling router (the VPN client) authenticates itself to the answering router (the VPN server), and for mutual authentication, the answering router authenticates itself to the calling router. In a site-to-site VPN connection, the packets sent from either router across the VPN connection typically do not originate at the routers.
A salesman has been given a company laptop computer. They are currently attending a conference in another country but need to access their company’s network and servers. Explain how; if they have access to the Internet, they could use a VPN to gain secure access their company’s network. You may assume that the company network is also connected to the Internet via a Firewall.