Uses Of Computer Networks

Uses Of Computer Networks:- 

Before we start to examine Technical issues in detail, it is worth devoting some time to pointing

 out why people are intrested in computer networks and what they can be used for.

Networks For Companies:- 

Many organizations  have a substantial number of computers in operation, often located far apart 

For example a company with many factories may have a computer at each location to keep track 

of inventories monitor productivity and do the local payroll. intially each of these computers may 

have worked in isola-tion from of others but at some point managment may have decided to 

connect them to be able to extract to and correlate information about the entire company.

       Put in slightly more general from, the issue here is resource sharing  and the goal is to make 

all programs equipment and especially data available to anyone on the network without regard to

 the physical location of the resource and the users. in other words the mere fact that a user 

happens to be 1000 km away from his data should not prevent him from useing the Data as though

 they were local. This goal may be summarized by saying that it is an attempt to end the "tyranny of geography." 

      A Second Goal is to provide High reliability by having alternative source of supply. for 

example all files could be replicated on two or three machine so if one of them is unavailable (due

 to a hardware failure), the other copies could be used. In addition the presence of multiple CPUs 

means that if one goes down the others may be able to take over its work, although at reduced 

performance. for military baking air traffic control nuclear reactor safety and many other 

applications the ability to continue operating in the face of hardware problems is of utmost importance.

    Another Goal is saving money. small computers have a much better price/performance ratio 

then large ones. Mainframes (room size computers) are roughly a factor of then faster then 

personal computers, but they cost a thousand times more. This imbalace has caused many systems

 desiners to build system consisting of personal computers one per user with data kept on one or 

more shared file server machines. in this model the users all called clients and the whole

arrangement is called the client-server model. It is illustrated in fig. 1-1.

   In the client-server model, communication generally takes the from of a request message from 

the client to the server asking for some work to be done..

 

 

The server then does the work and sends back the reply. usually, there are many clients using a small number of servers.

     Another networking goal is scalabilty, the ability to increase system performance gradually as

the workload grows just by adding more processors. With centralized mainframes, when the 

system is full it must be  replaced by a larger one, usually at great expense and even greater

 disruption to the users. with the client-server model, new clients and new servers can be added as needed.

    Yet another Goal of setting up a computer network as little to do with technology at all a 

computer can provide a powerful communication  medium among widely separated employees   

  Using a network, it is easy for two or more people who live for apart to write a report together. 

when one worker makes to change to an online document, the others can see the change 

immediately, insted of waiting several days for a latter. such a speedup makes impossible. In the

long run, the use of networks to enhance human to human communication will probably prove 

more important then technical goal such as improved reliability....