What is Computer Network ?

What is Computer Network

During the 1950's, all the computer were similar in the one respect. They had a main memory, a Central Processing Unit (CPU) and peripherals. The CPU and memory were central to the system. Since then a new generation of computing has emerged in which computation and data storage not require to be centralized. A user can retrieve a program from one place, run it on any of a variety of processors and transmit the result to the third location.

A computer network is an interconnected connection of autonomous computers. Here the word interconnected means that computers are linked with each other via some media (Guided or Unguided Media). The guided media includes copper wire, coaxial or fiber optics cable. The wireless communication (unguided media) can be either through microwave, radio communication or satellite.

A network allows many users to share a common pathway to communicate with each other. Networks can be used between people, between computers and people between computers and equipment or between computers.

Categories of Networks / Types of Networks

Generally, networks can be categorized into the following main types - LAN, MAN and WAN. The network category is determined by its size, its ownership, distance it covers and its physical structure.

1. Local Area Network (LAN) --

A local area network (LAN) is a computer network covering a small physical area, like a home, office, or small group of buildings, such as a school, or an airport. The defining characteristics of LAN's in contrast to Wide Area Networks (WAN's), include their usually higher data-transfer rates, smaller geographic place, and  lack of need for leased telecommunication lines. A networked office building, school, or home usually contains a single LAN, though sometimes one building will contain a few small LANs (perhaps one per room), and occasionally a LAN will span a group of nearby buildings.

A LAN is useful for sharing resources like files, printers, games or other applications. Most local area networks are built with relatively inexpensive hardware such as Ethernet cables, network adapters, and hubs. In addition to operating in a limited space, LANs are also typically owned, controlled, and managed by a single person or organization. They also tend to use certain connectivity technologies, primarily Ethernet and Token Ring.

2. Metropolitan Area Network (MAN) -

Metropolitan  area networks or MANs, are large computer networks usually spanning a city. They typically use wireless infrastructure such as microwave, radio, or infra-red laser link or Optical fiber connections to link their sites. This networks spans a physical area larger than a LAN but smaller than a WAN. A MAN is typically owned an operated by a single entity such as a government body or large corporation.

3. Wide Area Network (WAN) --

A computer network that spans a relatively large geographical area i.e., any network whose communication links cross metropolitan, regional, or national boundaries. In other words, WAN is a digital communication system used nationwide or worldwide. In this network, computers and small networks are inter-connected without cables but with the help of telephone lines, microwave and satellite links. The largest and most well-known example of a WAN is the Internet.

Other types of Area Networks

While LAN, MAN, and WAN are by far the most popular network types mentioned, you may also commonly see references to these others-

(a) Wireless Local Area Network (WLAN) :-

LAN stands for Local Area Network, so a wireless LAN is simply a network linking two or more computers without wires (cables). This links two or more computers or devices using spread-spectrum or OFDM modulation technology to enable communication between devices in a limited area. This gives users the mobility to move around within a board coverage area and still be connected to the network.

(b) System Area Network (SAN) :-

It is also known as Storage Area Network, Server Area Network, or sometimes Small Area Network. It connects servers to data storage devices through a technology like Fiber Channel.

(c) Campus Area Network (CAN) :-

It is also called Controller Area Network, or sometimes Cluster Area Network. This type of network spans multiple LANs but smaller than a MAN, such as on a university or local business campus. It links high-performance computers with high-speed connections in a cluster configuration.

(d) Personal Area Network (PAN) :-

It is a computer network organized around an individual person. Personal area network 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 wirelessly. USB and FireWire technologies often link together a wired PAN while wireless PANs Typically use Bluetooth or sometimes infrared connections. Bluetooth PANs are also called piconets. Personal area networks generally cover a range of less than 10 meters (about 30 feet).

(e) Desk Area Network (DAN) :-

A Desk-Area Network (DAN) is a small local system in which devices, such as multimedia devices, are taken out of the workstation and connected directly to the network. Workstations access these devices over the network and coordinate the movement of information streams among the different parts of the system.