LAN and MAN

Local Area Network: They are the privately-owned network within a single building or campus of upto a few kilometers in size. In the days before personal computers, a site might have just one central computer, with users accessing this via computer terminals over simple low-speed cabling. Networks such as IBM's SNA (Systems Network Architecture) were aimed at linking terminals or other mainframes at remote sites over leased lines—hence these were wide area networks. The first LANs were created in the late 1970s and used to create high-speed links between several large central computers at one site. It was the the time for the growth of LAN with the introduction of  CP/M and DOS based personel computers the requirement for such a kind of system began where the connectivity between the dozens of computers was needed. The initial attraction of networking then was generally to share disk space and printers, which were both very expensive at the time. There was much enthusiasm for the concept and for several years from about 1983 onward computer industry gurus would regularly declare the coming year to be “the year of the LAN”. LAN’s are distinguished from other kinds of networks by three characteristics: 1. their size 2. their transmission technology and 3. their topology. They are restricted in size which means that the worst case transmissiontime is bounded and known in advance. There are various standards set by IEEE for LAN for example IEEE 802.3 which I spopularly known as Ethernet. 

Metropolitan Area Network: 

Metropolitan Area Networks or MANs are large computer networks usually spanning a campus or a city. The best way to assume the picture of this type of network is to have example of the cable television network available in many cities. Also the universities and colleges may have many LAN connected among themselves to form a MAN situated in a site of a few square kilometers. These man could link among themselves to form a WAN. The technologies used for the puprose are ATM, FDDI and SMDS. The standard provided by IEEE for such a kind of network is IEEE 802.6 or popularly known as Distributed Queue Dual Bus (DQDB). Using this standard the network can extend upto 30 miles and the operating speed is 34 to 155 Mbps