LAN or local area network is one of the types of computer networks. This type lets you establish a network in a limited area such as in a school, laboratory, office or home using any of the communication technologies available.
Characteristics of Local Area Network
The characteristics that define a local area network and differentiate it from a wide area network are:
1. The rate of transfer of data is higher than the other networks. It typically lies in the range of 1 – 10 mbits per second when compared to the 100 kbits per second of wide area networks.
2. They can be implemented only over a small geographical area.
3. They do not require nay leased communication lines.
4. All the devices share one and the same transmission medium. For example, a common cable. Thus when one device transmits some data, it is received by all the others. Therefore it can also be considered to be a broadcast network.
5. In a local area network, transmission usually takes place in the form of data packets. For transmitting a message, it is split in to various small packets.
6. The distribution of the machines is limited i.e.., the machines should be located typically around 1 km and maximum up to 10 km.
7. The connections to a machine are restricted to one site.
8. Sharing of resources is possible. For example, the users use a site and access the common printer, file servers and so on.
9. The ownership of all the network elements is single.
10. Even incompatible networks can be connected to the network such as personal microcomputers, terminals, large mainframes and so on.
– The entire network is restricted to a certain diameter or a single private site.
– The connection of non-compatible equipment with the network is attained through an NIC or network interface controller.
– This is actually a protocol converter and a sophisticated emulator program.
– The device has to be connected to the port on the NIC.
– The input from the device is then translated by the NIC.
– But here it is required that the following communication characteristics of the devices should be specified:
1. Serial (whether synchronous or asynchronous) lines
2. Parallel lines
3. Physical handshake (whether software or hardware handshaking)
4. Data format (whether data is transferred as stream of bits or bytes)
5. Flow control (to prevent overrun)
6. Other protocols
– Earlier for LANs, technology standards such as the token ring and ARCNET were used.
– But nowadays technologies such as Wifi and Ethernet are preferred over twisted pair cabling for building a local area network.
– The initial networking was only limited to connections between the printers and storage devices and proved to be quite costly at that time.
– Later, a lot of enthusiasm was observed for the concept in the following years.
– Networking based up on TCP/IP was being used by the Unix computer workstations.
– A number of vendors had such workstations such as:
1. Sun microsystems
2. Hewlett Packard
3. Silicon graphics
– Though this area does not dominate the market these days, they still do affect the internet.
– AppleTalk, IPX, NBF have now been completely replaced by TCP/IP based networking.
– The grading of the LAN cable was done based up on grades of coaxial cable.
– The pattern in which the connections can be made is described by the network topology.
– For LANs mostly Ethernet has served as the physical layer and data link layer.