In general, the VPN - an association of local networks or individual machines that are connected to the public network into a single virtual (overlay) network that provides privacy and integrity of the transmitted information on it (transparent to the use
Many large and medium-sized companies who care about their information security, probably faced with the problem of detecting unauthorized access to your local network.
Obviously, the main reason for the rapid introduction of switches is lower compared to traditional routers, the cost of the devices and a significant reduction in the costs of the organization and support networks.
The Internet is a network of virtual networks. In 1991, we (then the USSR) knew about it a few dozen people who have just mastered e-mail (via RELCOM) and try what FidoNet. The first e-mail message was sent to US President Bill Clinton March 2, 1993.
Today is becoming increasingly urgent problem of congestion cable ducts that can be solved with the help of mikrotransheynoy laying fiber-optic cables.