COMPUTER NETWORKS - DEFINITION AND EXAMPLE                       

what is a computer network?
A group of two or more computer systems linked together. There are many types of computer networks,mainly including:

  • Local Area Network (LANs) : The computers are geographically close together (that is, in the same building).
  • Metropolitan Area Network (MAN) : The computers which are designed to work together within a data range which spans a city or a town.
  • Wide Area Network (WAN) : The computers are farther apart and are connected by telephone lines or radio waves.

    The protocol determines the following in a network:

    the type of error checking to be used..

     data compression method, if any.

     how the sending device will indicate that it has finished sending a message.

     how the receiving device will indicate that it has received a message.

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    local-area network
     

    A computer network that spans a relatively small area. Most LANs are confined to a single building or group of buildings. However, one LAN can be connected to other LANs over any distance via telephone lines and radio waves. A system of LANs connected in this way is called a wide-area network (WAN).

    Most LANs connect workstations and personal computers. Each node (individual computer ) in a LAN has its own CPU with which it executes programs, but it is also able to access data and devices anywhere on the LAN. This means that many users can share expensive devices, such as laser printers, as well as data. Users can also use the LAN to communicate with each other, by sending e-mail or engaging in chat sessions.

    There are many different types of LANs Ethernets being the most common for PCs. Most Apple Macintosh networks are based on Apple's AppleTalk network system, which is built into Macintosh computers.

    The following characteristics differentiate one LAN from another:

  • topology : The geometric arrangement of devices on the network. For example, devices can be arranged in a ring or in a straight line.
  • protocols : The rules and encoding specifications for sending data. The protocols also determine whether the network uses a peer-to-peer or client/server architecture.
  • media : Devices can be connected by twisted-pair wire, coaxial cables, or fiber optic cables. Some networks do without connecting media altogether, communicating instead via radio waves.
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    LANs are capable of transmitting data at very fast rates, much faster than data can be transmitted over a telephone line; but the distances are limited, and there is also a limit on the number of computers that can be attached to a single LAN.

    metropolitan-area network
     

    Short for Metropolitan Area Network, a data network designed for a town or city. In terms of geographic breadth, MANs are larger than local-area networks (LANs), but smaller than wide-area networks (WANs). MANs are usually characterized by very high-speed connections using fiber optical cable or other digital media.

    wide-area network
     

    A computer network that spans a relatively large geographical area. Typically, a WAN consists of two or more local-area networks (LANs).

    Computers connected to a wide-area network are often connected through public networks, such as the telephone system. They can also be connected through leased lines or satellites. The largest WAN in existence is the Internet.

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