Transcript Chapter 1 - Introduction

Computer Networks and Internets, 5e
By Douglas E. Comer
Lecture PowerPoints
By Lami Kaya, [email protected]
© 2009 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.
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Chapter 2
Internet Trends
© 2009 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.
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Topics Covered
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2.1
2.2
2.3
2.4
2.5
2.6
Introduction
Resource Sharing
Growth of the Internet
From Resource Sharing to Communication
From Text to Multimedia
Recent Trends
© 2009 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.
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2.1 Introduction
• This chapter
– considers how data networking and the Internet have changed since
their inception
– gives a brief history of the Internet that highlights some of the early
motivations
– describes a shift in emphasis from sharing centralized facilities to
fully distributed information systems
• Later chapters in this part of the text
– continue the discussion by examining specific Internet applications
– describe the communication paradigms available on the Internet
– explain the programming interface that Internet applications use to
communicate
© 2009 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.
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2.2 Resource Sharing
• Early computer networks were designed when computers were large
and expensive, and the main motivation was resource sharing
– Networks were devised to connect multiple users
• each with a screen and keyboard, to a large centralized computer
– Later networks allowed multiple users to share peripheral devices
• early networks were designed to permit sharing of expensive, centralized resources
• Department of Defense for Advanced Research Projects Agency
(DARPA or ARPA) interested in finding ways to share resources (1960s)
– Researchers needed powerful computers
• but these computers were very expensive
• the ARPA budget was insufficient to fund many computers
– ARPA planned to interconnect all computers with a network
• and devise software that would allow a researcher to use whichever computer was
best suited to perform a given task
• ARPA did the following to achieve the visionary work:
– gathered some of the best minds available
– focused them on computer network research
– hired contractors to turn the designs into a working system: ARPANET
• The research turned out to be revolutionary
© 2009 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.
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2.3 Growth of the Internet
• In less than 30 years
– the Internet has grown from an early research prototype connecting
a handful of sites to a global communication system
– the rate of growth has been phenomenal
• Figure 2.1 illustrates the growth with a graph
– The graph in Figure 2.1 uses a linear scale in which the y-axis
represents values from zero through five hundred fifty million
– Linear plots can be deceptive because they hide small details
• To understand the early growth rate
– look at the plot in Figure 2.2, which uses a log scale
– It shows that Internet has had exponential growth for over 25 years
– Internet has been doubling in size every nine to fourteen months
© 2009 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.
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2.4 From Resource Sharing to Communication
• As it grew, the Internet changed in two significant ways:
– First, communication speeds increased dramatically
– Second, new applications arose that appealed to a broad crosssection of society
– Internet is no longer dominated by scientists and engineers, scientific
applications, or access to computational resources
• Two technological changes fueled a shift away from
resource sharing to new applications:
– Higher communication speeds
• enabled applications to transfer large volumes of data quickly
– The advent of powerful, affordable, personal computers
• provided the computational power needed for complex computation and
graphical displays, eliminating most of the demand for shared resources
© 2009 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.
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2.5 From Text to Multimedia
• One of the most obvious shifts has occurred in the data being sent
across the Internet
• Figure 2.3 illustrates one aspect of the shift
– As the figure indicates, Internet communication initially involved textual data
– By the 1990s, applications arose that allowed users to transfer images easily
– By the late 1990s, users began sending video clips and full-motion videos
• Figure 2.4 illustrates that a similar transition has occurred in audio
• Multimedia characterizes data that contains a combination of text,
graphics, audio, and video
• Much of the content available on the Internet now consists of multimedia
• Furthermore, quality has improved as higher bandwidths have made it
possible to communicate high-resolution video and high-fidelity audio
© 2009 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.
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2.5 From Text to Multimedia
© 2009 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.
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2.6 Recent Trends
• New technologies and new applications continue to emerge
• Some of the most significant transitions have occurred as
traditional communication systems
– such as the voice telephone network and cable television, moved
from analog to digital and adopted Internet technology
– In addition, support for mobile users is accelerating
• Figure 2.5 lists some of the changes
• One of the most interesting aspects of the Internet
– arises from the way that Internet applications change even though
the underlying technology essentially remains the same
• Figure 2.6 lists types of applications that have emerged
© 2009 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.
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2.6 Recent Trends
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2.6 Recent Trends
• The availability of high-quality teleconferencing systems
– such as Cisco's TelePresence, is significant for businesses because
such systems permit meetings to occur without travel expense
• in many businesses, reducing travel expenses lowers costs significantly
• Some social networking applications such as
– Facebook
– Second Life
– YouTube
• Social network apps are fascinating
– because they have created new social connections - sets of people
know each other only through the Internet
– sociologists suggest that such applications will enable more people
to find others with shared interests and will foster small social groups
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