Telecomunicaciones

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CHAPTER 1

EVOLUTION OF COMPUTER NETWORKS

EVOLUTION
OF COMPUTER
NETWORKS
CHAPTER OUTLINE

1.1 INTRODUCTION
1.2 ROOTS OF COMPUTER NETWORKS
1.2.1 Computer Networks
as a Result of the Computing
and Communications Technologies
1.2.2 Batch-Processing Systems
1.2.3 Multiterminal Systems: Prototype
of the Computer Network
1.3 FIRST COMPUTER NETWORKS
1.3.1 First Wide Area Networks (WANs)
1.3.2 FirstLocal Area Networks (LANs)
1.4 CONVERGENCE OF NETWORKS
1.4.1 Convergence of LANs and WANs
1.4.2 Convergence of Computer
and Telecommunications Networks
CHAPTER SUMMARY
REVIEW QUESTIONS
PROBLEMS

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N ETWORKING B ASICS

1.1 INTRODUCTION

Studying the evolution of any area of science or technology will not only stimulate your
natural curiosity, it will also give you a deeperunderstanding of the main achievements in
this area, make you aware of the existing trends, and help you to evaluate the prospects of
specific developments. Computer networks emerged relatively recently, in the late 1960s.
They have inherited many useful properties from their predecessors, namely, older and
more widely adopted telephone networks. This is not surprising, since both computers
and telephonesare universal instruments of communications.
However, computer networks have brought something new into the world of communications — namely, the practically inexhaustible store of information accumulated by
human civilization during the several thousand years of its existence. This information
store is continuing to grow at a steadily increasing rate. This became especially noticeable
in themid-1990s, when the rapid growth of the Internet clearly demonstrated that free
and anonymous access to information and instant, written communications were highly
valued by most individuals.
The influence of computer networks on other types of telecommunications networks
resulted in network convergence, a process that started long before the Internet. Digital
voice transmission in telephone networkswas one of the first signs of that convergence.
More recent indications of convergence are the active development of new services in
computer networks that previously were the prerogatives of telephone, radio, and TV
networks, such as Voice over IP (VoIP), radio broadcasts, and TV services. The process of
convergence is continuing, though without offering clear signs of its future. However,
knowingthe evolution of computer networks, which is described in this chapter, makes it
easier to understand the main problems that developers of computer networks must face.

1.2 ROOTS OF COMPUTER NETWORKS

KEY WORDS: mainframe, batch-processing systems, time-sharing systems, multiterminal systems, computer network, datacom network or data-transmission network, Grosch’s Law, Local Area Networks (LANs),standard LAN technologies:
Ethernet, Arcnet, Token Ring, FDDI

1.2.1 Computer Networks as a Result of the Computing and Communications
Technologies Evolution
The computer networks covered in this book 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 thewater-supply sys-

CHAPTER 1

Telecommunications

EVOLUTION OF COMPUTER NETWORKS

Computing

Computer networks

Figure 1.1 Evolution of computer networks at the interfaces of the computing and
communications technologies

tem of ancient Rome. But no matter how remote and distinct by their nature different
networks can seem, they all have something in common. For example, it is possible to
draw a clearanalogy between the components of electric networks and those of any largescale computer network. That is, the information resources found in computer networks
correspond to power stations; communications 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 in electric networks,...