S-72.1120 Data Communications and Protocols – Spring 2008

Case 2: Virtual Private Network

A local area network (LAN) connects the computers of a company within a single building or a small group of buildings. The computers within the network can share files and devices, such as printers. Nowadays, practically all LANs are Ethernet networks.

However, the company may have a number of offices in several locations. In that case the separate netwoks at the scattered offices may be connected into one virtual private network. To the ordinary user the network appears to be a single LAN, but actually the local LANs are connected to each other by way of some wide area network, e.g. the public telephone network.

Find out what happens to a single message on its way from the sender in one subnetwork to the ultimate receiver in another subnetwork and what kind of services are available to connect the LANs to each other.