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Computer Network is defined in the section 2 (1) (J) of IT Act 2000. “Computer network” means the inter-connection of one or more computers or computer systems or communication devices through:

1. the use of satellite, microwave, terrestrial line, wire, wireless or other communication media;
2. terminals or a complex consisting of two or more inter-connected computers or communication device whether or not the inter-connection is continuously maintained.

The aforesaid definition of computer network has to be understood in the light of the definition of computer 2 (1) (i) and communication devices [ section 1 (1) (ha) ] as it talks about inter-connection of one or more computers. It identifies both virtual and physical computer networks——whether wired or wireless.

Internet ,Satellite phones , mobile phones , net telephony, ATM machines , are examples of [2 (j) (i)] and LAN , WAN, VPN, Wi-Fi , are examples of [2 (j) (ii)].

Generally there are three types of computer networks based on their size , its ownership , distance it covers and its physical structure.

A group of computers which are connected to each other and follow similar usage protocols for the purpose of sharing information and having communications provided by the networking nodes is called a Computer Network.

A network may be small where it may include just one system Or maybe as large as what one may want. The nodes may further be classified into various types. These include:

• Personal Computers.
• Servers.
• Networking Hardware.
• General Hosts.

Networking can be classified into three types:

•  Types of Computer Networks.
• Topology.
• Interpreters.

Types of Computer Networks :

There are five main types of Computer Networks:

1.  LAN (Local Area Network) –

• Systems connected in a small network like in a building or a small office.
• It is inexpensive.
• It uses Ethernet or Token-ring technology.
• Two or more personal computers can be connected through wires or cables acting as nodes.
• Transfer of data is fast and is highly secure.

2.  PAN (Personal Area Network) –

• The smallest computer network.
• Devices may be connected through Bluetooth or other infra-red enables devices.
• It has a connectivity range of up to 10 metres.
• It covers an area of up to 30 feet.
• Personal devices belonging to a single person can be connected to each other using PAN.

3. MAN (Metropolitan Area Network) –

• A network that can be connected within a city, for example, cable TV Connection.
• It can be in the form of Ethernet, ATM, Token-ring and FDDI.
• It has a higher range.
• This type of network can be used to connect citizens with the various organisations.

4. WAN (Wide Area Network) –

• A network which covers over a country or a larger range of people.
• Telephonic lines are also connected through WAN.
• Internet is the biggest WAN in the world.
• Mostly used by Government Organisations to manage data and information.

5. VPN (Virtual Private Network): –

• A network which is constructed by using public wires to connect to a private network.
• There are a number of systems which enable you to create networks using the Internet as a medium for transporting data.
• These systems use encryption and other security mechanisms to ensure only authorised users can access.