A network may be a small group of interlinked computers to a chain of a few hundred computers of different types (for example personal computers, minicomputers , mainframes etc.). These computers may be localised or spread around the world. Thus networks vary in terms of their size and complexity. Various types of networks are discussed below:
PAN (Personal Area Network)
A Personal Area Network is a computer network organized around an individual person. Personal area networks typically involve a mobile computer, a cell phone and/or a handheld computing device such as a PDA. You can use these networks to transfer files including email and calendar appointments, digital photos and music. Personal area networks can be constructed with cables or be wireless. USB and FireWire technologies often link together a wired PAN, while wireless PANs typically use bluetooth or sometimes infrared connections. Bluetooth PANs generally cover a range of less than 10 meters (about 30 feet). PANs can be viewed as a special type (or subset) of local area network (LAN) that supports one person instead of a group.
LAN (Local Area Network)
In a LAN, network devices are connected over a relatively short distance. They are generally privately owned networks within a single building or campus, of up to a few kilometres in size. LANs can be small, linking as few as three computers, but often link hundreds of computers used by thousands of people. This means that many users can share expensive devices, such as laser printers, as well as data on the LAN. Users can also use the LAN to communicate with each other, by sending mails or engaging in chat sessions.
MAN (Metropolitan Area Network)
This is basically a bigger version of LAN and normally uses similar technology. It might cover few buildings in a city and might either be private or public. This is a network which spans a physical area ( in the range of 5 and 50 km diameter) that is larger than a LAN but smaller than a WAN. MANs are usually characterized by very high-speed connections using optical fibres or other digital media and provides uplink services to wide area networks (WANs) and the Internet. For example in a city, a MAN, which can support both data and voice might even be related to local cable television network.
WAN (Wide Area Network)
As the term implies, WAN spans a large geographical area, often a country or a continent and uses various commercial and private communication lines to connect computers. Typically, a WAN combines multiple LANs that are geographically separated. This is accomplished by connecting the different LANs using services such as dedicated leased phone lines, dial-up phone lines, satellite links, high speed fibre optic cables and data packet carrier services. Wide area networking can be as simple as a modem and remote access server for employees to dial into, or it can be as complex as hundreds of branch offices globally linked using special routing protocols and filters to minimize the expense of sending data sent over vast distances.