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Roots of Computer Networks


Computer Networks as a Result of the Computing and Communication Technologies Evolution

The computer networks covered on my site are obviously not the only type of networks created throughout human civilization. Possibly the oldest example of a network covering large territories and serving multiple clients is the water supply system of ancient Rome. But no matter how remote and distinct by nature different networks can seem, they all have something in common. For example, it is possible to draw a clear analogy between the components of electric networks and those of any large scale computer networks. That is, the information resources found in computer networks correspond to Power Stations; communication links of computer networks are analogous to high voltage transmission lines, and access networks are similar to transforming stations.  Finally, both in computer networks and electric networks, one can find client terminal—End-user workstations in computer network and household electric appliances in electric network.

Computer networks are also known as datacom or data transmission networks, represent a logical result of the evolution of two of the most important scientific and technical branches of modern civilization—Computing and Telecommunication technologies.

On one hand, computer networks represent a particular case of distributed computer systems in which a group of computers operate in a coordinated manner to perform a set of interrelated tasks by exchanging data in an automated mode. Computer networks can also be considered a means for transmitting information over long distances. To do so, computer networks implement various methods of data encoding and multiplexing that are widely adopted in telecommunication systems.

Batch-Processing System

First consider the origins of computer networks. The computers of 1950s – large, bulky and expensive – were intended for a small number of privileged users. Quite often, these monstrous constructions occupied entire buildings. Such computers were not able to serve users interactively. Instead they batched jobs and delivered results later.

Batch-processing systems were usually based on mainframes and were powerful and reliable universal computers. Users would prepare punched cards containing data and program code and then transfer these cards to the computing centre. Operators would enter these cards into the computer and users would receive results a day later in the form of printout. Thus a single punch card containing error would mean a delay of at least 24 hours.

Fig. 1.2. Centralized system based on a mainframe

Obviously, from end users’ point of view, an interactive mode of operating that allows them to manage the processing of their data on the fly from the terminal is more convenient. The interests of end users were substantially neglected at earliest stages of the evolution of computer systems. The efficiency of the operations of the most expensive component of the computer — The Processor—was regarded as of paramount importance, even at the expense of the user productivity.

Multi-terminal Systems: Prototype of the Computer Network

As processors became cheaper, in the early 1960s, new methods of organizing computer processing appeared. These methods provided the possibility of taking end user convenience into account. Thus multi-terminal systems evolved. In such time-sharing systems, the computer was at disposal of several users. Users had their own terminals from which they could communicate with the computer. The response time of the computer was short enough to mask that the computer served multiple users in parallel.

Terminals moved out of computing centres and onto desktops over entire organizations. Although processing power remained fully centralized, multi-terminal systems looked like Local Area Networks (LANs). End user perceived working at the terminal, practically the same way that most people now view working at the PC connected to the network. User could access shared files and peripheral devices and maintain the illusion of using the computer in an exclusive mode, since the user could start any required program at any moment and receive the results almost immediately. (Some people were even convinced that all calculations were made somewhere inside the computer display.)

Multi-terminal systems, working in time-sharing mode, became the first step towards the developments of LANs.

However, the evolution still had a long way to go before LANs appeared, because multi-terminal systems retained the essential features of centralized data processing despite superficial resemblance to distributed systems.

Organization didn’t feel a pressing need for LANs. Within a single building, there was nothing to connect to using a network. Most companies could not afford the luxury of purchasing more than one computer. During this period, the so called Grosch’s Law (named after Herbert Grosch) was universally true. It represented empirically the technological level at that time. According to this law, the cost of computer system increases as the square root of the computational power of the system. Hence it was more profitable to purchase one powerful machines rather than two less powerful ones, because their total computational power proved to be significantly lower than that of the expensive machine.

Source: Internet

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