VIRTUAL PRIVATE NETWORK

Large organisation will usually have to employ two types of network.
1.PRIVATE NETWORK
2.GLOBAL NETWORK

PRIVATE NETWORK
This type of network doesnt require internet connection and it is used only to share information between the computers in a organisation.These organisation which have branches all over the world have to be connected through wires which constitute a WAN.

GLOBAL NETWORK
This internet connection is required for connecting to external world.

HYBRID NETWORK
To accomplish the above two needs the organisation employs two routers one to connect to the private and another to connect to external world.

NEED FOR VPN
The above method has major disadvantage that using a private network with WAN is very costly since it requires connection to branches in all parts with wires.Also the global network requires monthly payment.To integrate both the cost ICANN introduced VPN which provides both the private and global connection with a single connection.The data packets destined for private computer is encapsulated with IPsec such that it will be deciphered only by private computer.This process is called tunneling.As the network seem to be private it is not but it make use of global line for communication.Thats why the name VIRTUAL PRIVATE NETWORK.