WIDE AREA NETWORK
WAN]:Wide area networking combines multiple LANs that are geographically separate. This is accomplished by connecting the different LANs using services such as dedicated leased phone lines, dial-up phone line (both synchronous and asynchronous), satellite link, and data packet carrier services. It can be as simple as a modem and remote access server for employees to dial into, or it can be as complex using special routing protocols and filters to minimize the expense of sending data sent over vast distances.
METROPOLITAN AREA NETWORK
MAN consists of a computer network across an entire city college campus or small region. A MAN is larger than a LAN. Depending on the configuration, this type of network can cover an area from miles to tens of miles. A MAN is often used to convert several LANs together to form a bigger network. It is specifically designed for security purpose.
VIRTUAL PRIVATE Network
[VPN]: VPN is a technology that allows a network administrator to create a secure connection over a loss-secure network between computer and the internet. It protects information privacy by allowing the administrator to anonymously appear to be in any network. A VPN is beneficial because it guarantees an appropriate level of security and privacy to the connected systems. This is extremely useful when the existing network infrastructure alone cannot support it.