Models of Network Computing

After you have the necessary prerequisites for network communication, a structure must be put in place that organizes the way communication and sharing occur. Many models are recognized. We will discuss very basic two models:

1. Centralized Computing
2. Distributed Computing

Various types of network are derived from these two basic models of computing. (Some people may include 'Collaborative Computing', but this type of computing is the subtype of 'Distributed Computing').

Centralized Computing

The earliest computers were large, expensive, and difficult to manage. Originally, these large mainframe computers were not networked in the sense you are familiar with today. Jobs were entered into the system by reading commands from card decks. The computer would execute one job at a time and generate a printout when the job was complete. Terminals, which came later, enabled users to interact with the centralized computer, but terminals were merely input / output devices that had no independent processing power. All processing still took place on the mainframe, hence the name centralized computing. Networks, therefore, served little purpose other than to deliver commands to and results from the powerful centralized processing device. Large IBM and Digital (DEC) networks often still operate on this model, but Microsoft has largely ignored it.

In summary, the centralized computing model involves the following:

1. All processing takes place in the central, mainframe computer.
2. Terminals are connected to the central computer and function only as input / output devices.
3. Networks may be employed to interconnect two or more mainframe computers. Terminals connect only to the mainframe, never to each other.

This early computing model worked well in large organizations, but was not flexible and did not scale down to meet the needs of smaller organization. As such, new ways to sharing information were needed to allow computing power to be shared efficiently on smaller networks.

Distributed Computing

As personal computers were introduced to organizations, a new model of distributed computing emerged. Instead of concentrating computing to a central device, PCs made it possible to give each worker an independent, individual computer. Each of these PCs can process and store data locally, without assistance from another machine. This meant that groups who previously had found the cost of a mainframe environment prohibitive were able to gain the benefits of networking at far-reduced cost. Under the distributed computing model, networking has evolved to enable the many distributed computers to exchange data and share resources and services among themselves. Note that these machines need not be considered equals. A Windows NT file server, for instance, is considered to be a part of a distributed network. This server stores and retrieves files for other machines, but doesn't do the thinking for these machines as a mainframe would have done in the centralized computing model.

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