LAN and MODEM for internet

The Internet is a vast network of computers all over the world.In fact,the internet is actually a collection of smaller networks called local area networks or LANs.LANs connect computers across a very small geographical region,usually not more than a few kilometers wide.A network within a university would be a good example.In a LAN,all computers have access to a common channel of communication,usually a set of wires or a cable.Any computer that wishes to communicate with some other computer,uses this common cable.The main communication channel itself is independent of the computers that use it.This ensures that even if some computers malfunction,the rest of the LAN continues to operate.This also ensures that the speed of the LAN does not depend on the speeds of individual computers.Traditional LANs have speeds of 10 to 100 megabits per second or Mbps.Newer LANs are capable of speeds if hundreds of Mbps.

The Internet is somewhat similar to a LAN in the sense that it too is just a common communication channel independent of the communicating computers.but in addition to using simple cables,communication is carried out over conventional communication media like telephone networks and satellites.Another difference between a LAN and the internet that the internet uses special computers called is routers to direct the flow of information through its elaborate network.To send information to its destination using the most suitable path,routers use complex routing schemes called routing algorithms.Another very important role played by routers is the integration of different LANs.

The term 'internet' is derived from the more general term inter-network.To differentiate between the two,let us state that while an inter-network is a theoretical concept referring to a vast network of computers,the internet is its practical application; a vast network that exists in our times to link strategic organisations and private individuals all over the world.

The most popular way a distant or remote computer is connected to a LAN is by the use of conventional telephone lines.The distant computer connects to the telephone network using a special device called a modem.There must be a modem connected to the remote computer as well to the LAN.

The modem is required for a special reason.The reason is that telephone lines do not transmit information in the format used by the computer.Telephone lines have their own format to transmit information.So a device is needed which can translate between the format as understood by the computer and the one understood by the telephone lines.Such a device is the modem.Modems at both the ends of the network are capable of both modulation and demodulation,and thus,two-way communication is possible.In fact the term modem is short for MOdulator-DEModulator.

thus,using modems,computers that are not in the proximity of the LAN,may be effectively connected to it.Hence,because they can connect to a LAN,computers may connect to the internet if the LAN itself is connected to one of the internet's routers.