Networks
                 Based on 
               geographical 
               distribution
         Local Area         Metropolitan          Wide Area 
       Network (LAN)        Area Network       Network (WAN)
                                (MAN)
   Local Area Network (LAN)
   • A Local Area Network (LAN) is a group of interconnected computers, 
    printers and other devices that are situated within a radius of 1 km 
    and normally they belong to a single organisation.
   • All the computers in the network need to have a Network Interface 
    Unit (NIU) which performs interface functions while data transmission. 
   • Whenever some data is sent from one computer to another computer 
    in the network, the data is sent to NIU along with the address of that 
    computer. 
   • After sending the command to NIU the computer becomes free and 
    the NIU delivers the data safely to the destined computer’s NIU and 
    then the other computer receives the data received by its NIU.
   The following are the salient features of a LAN:-
   1) LAN is limited by distance.
   2) The rate at which data is transferred between two computers in the network 
   is very high.
   3) Cables are used as primary medium of data transmission.
   4) The users share hardware as well as software resources through LAN.
   Metropolitan Area Network (MAN) 
  • A Metropolitan Area Network (MAN) is a data network that 
   interconnects the users with computer resources, usually with a spread 
   of a town or a city, using fiber-optical cable or other digital media.
  • MAN covers a larger geographical area than LANs but a smaller 
   geographical area than Wide Area Network (WANs).
  • The commonly used technologies for MANs are Asynchronous Transfer 
   Mode (ATM), Distributed Que Dual Bus (DQBS), Switched Multi 
   megabit Data Service (SMDS) etc. 
       The following are the features of MANs: 
       1.   The connections between computers are through the local 
            telephone network.
       2.   Usually a dedicated leased line is provided by the telephone 
            company to each user, so that, no one else can make 
            unauthorised use of the network.
       3.   The network size remains between LAN and MAN.
       4.   A MAN acts as a high speed network to enable users share 
            regional resources.
       5.   Unlike LAN, a MAN is not generally owned by a single 
            organisation. It may be owned by either a consortium of users or a 
            single network service provider who sells the services to the users.