Table Of ContentMatthew N. O. Sadiku
Cajetan M. Akujuobi
Fundamentals
of Computer
Networks
Fundamentals of Computer Networks
Matthew N. O. Sadiku
Cajetan M. Akujuobi
Fundamentals of
Computer Networks
Matthew N. O. Sadiku Cajetan M. Akujuobi
Prairie View A&M University Prairie View A&M University
Prairie View, TX, USA Prairie View, TX, USA
ISBN 978-3-031-09416-3 ISBN 978-3-031-09417-0 (eBook)
https://doi.org/10.1007/978-3-031-09417-0
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Preface
Computer networking is an exciting and fascinating field of study. It is the
fastest growing technology in our society. A computer network is a connec-
tion of two or more autonomous computers and other devices so that they can
communicate and share information. It enables sharing of files, data, and
devices such as printers. It facilitates interpersonal communications and
allows users to communicate via various means: email, instant messaging,
chat rooms, telephone, video telephone calls, and video conferencing.
Computer networking relies on the related discipline of electrical engineer-
ing, computer engineering, and computer science.
Earlier, computer networks consisted of mainframes in a building.
Computers became more powerful, smaller, and less expensive, to the point
that the typical desktop PC is equivalent to an early mainframe. This led to
the need to network those devices within the workplace to form a local area
network (LAN) that will allow PC users to share access to hosts, databases,
printers, etc.
The growth of computer networks from local area networks (LANs) to the
Internet has been rapid. Right now, we have many different types of computer
networks. They are often classified in terms of their geographical coverage:
• Local area network (LAN), which covers a building or campus
• Metropolitan area network (MAN), which covers a city
• Wide area network (WAN), which can cover a nation, continent, or any-
where on Earth
The most popular computer network is the Internet, which is a WAN. Global
Internet enables its users to access enormous amount of information
worldwide.
Computer networks have emerged as the integration of technologies in
computer and communication, and their evolution is tightly related to the
advances in these two areas. Our modern society has been greatly affected by
computer networks, especially the Internet. Computer networks have changed
how we live, educate, entertain, and do business. Within a short time, com-
puter communication networks have become an indispensable part of busi-
ness, industry, and entertainment. Industries, government agencies, military,
education, libraries, healthcare, law enforcement, justice, manufacturing,
financial services, insurance, transportation, aerospace, telecommunication,
energy, retail, and utilities are becoming increasingly dependent on the
vii
viii Preface
computer networks. People now can easily and conveniently connect to any-
body anywhere in the world, send emails, access information, do shopping,
and chat on the Internet without leaving their homes.
The major objectives of this book are:
• To introduce students to how computer networks work
• To familiarize students with international standards for computer
networks
• To bring to students’ awareness the newly emerging technologies in com-
puter networking
Most books on computer networks are designed for a two-semester course
sequence. Unfortunately, electrical and computer engineering has grown con-
siderably, and its curriculum is so crowded that there is no room for a two-
semester course on computer networks. This book is designed for a 3-hour
semester course on computer networks. It is intended as a textbook for senior-
level students in electrical and computer engineering. Their mathematical
background should include calculus and probability. But no advanced math-
ematics is required.
This book is intended to present computer networks to electrical and com-
puter engineering students in a manner that is clearer, more interesting, and
easier to understand than other texts. All principles are presented in a lucid,
logical, and step-by-step manner. As much as possible, we avoid wordiness
and giving too much detail that could hide concepts and impede overall
understanding of the material. Ten review questions in the form of multiple-
choice objective items are provided at the end of each chapter with answers.
The review questions are intended to cover the little “tricks” which the exam-
ples and end-of-chapter problems may not cover. They serve as a self-test
device and help students determine how well they have mastered the chapter.
A problem solution manual will be provided, and it will be available directly
from the publisher.
The book is organized to serve as a textbook for an undergraduate course
in computer networks. The book is divided into 12 chapters, with each chap-
ter self-contained.
Chapter 1: “Introduction.” The introductory chapter defines computer net-
works and provides examples. It covers common protocols, types of com-
puter network (LANs, MANs, and WANs), and popular applications of the
computer networks.
Chapter 2: “Digital Communications.” The idea of a digital communication
system and all of the various components that make up the entire system
are discussed in this chapter. This includes the transmission media, the
encoding techniques, bit/byte stuffing, multiplexing, and the different
types of switching techniques.
Chapter 3: “Network Models.” In this chapter, the network models such as the
Open Systems Interconnection (OSI) and the Transmission Control
Protocol/Internet Protocol (TCP/IP) models are presented. This chapter
Preface ix
also discusses the different networking applications—the internetworking
system devices and Signaling Systems No. 7 (SS7).
Chapter 4: “Local Area Networks.” This chapter covers the local area net-
works (LANs) and their different types. It mentions the advantages and
disadvantages of the different topologies of LAN. All of the operational
access methodologies including the controlled access devices are also
discussed.
Chapter 5: “The Internet.” This chapter introduces TCP/IP protocols and IP
addresses. It discusses important issues facing the Internet: privacy, secu-
rity, and safety. It also covers the next-generation Internet (IPv6) and
Internet2, which is the future of Internet.
Chapter 6: “Intranets and Extranets.” The excitement created by the Internet
(a public network) has been transferred to modern networks called
intranets and extranet. This chapter presents an introduction to intranets
and extranets as two of the growing applications of Internet.
Chapter 7: “Virtual Private Networks.” This chapter covers the main charac-
teristics of virtual private networks (VPN), different types of VPNs, vari-
ous applications of VPNs, and the benefits and challenges of VPNs.
Chapter 8: “Digital Subscriber Line.” The chapter discusses digital subscriber
line (DSL). DSL is a high-speed data technology which is also referred to
as a broadband telecommunication system and constitutes part of the
access technology network. The comparison between the different types
of DSL is also made.
Chapter 9: “Optical Networks.” This chapter gives an introduction to optical
networks. It discusses some of the main optical components. It covers
various optical networks: WDM-based networks, passive optical net-
works, SONET, all-optical networks, and free-space optics. It provides
some applications of optical networks.
Chapter 10: “Wireless Networks.” This chapter provides a brief overview of
wireless communication networks. It considers wireless local area net-
works (WLANs), wireless metropolitan area networks (WMANs), wire-
less wide area network (WWAN), and wireless personal area network
(WPAN). It explains cellular network, satellite networks, and wireless
sensor network (WSN).
Chapter 11: “Network Security.” In this chapter, the important aspects of net-
work security are discussed. The chapter describes malware, firewall,
encryption, digital signatures, intrusion detection and prevention, and
cybersecurity and how they relate to network security.
Chapter 12: “Emerging Technologies.” This chapter discusses some of the
major emerging technologies including Internet of Things (IoT), big data,
smart cities, blockchain technology, cloud computing, fog computing,
edge computing, 5G networks, and cybersecurity issues. Steganography,
an information security technique used in cybersecurity related issues, is
also covered.
Appendix A covers old technologies such as X.25, Frame Relay, ISDN
and BISDN, ATM, and MPLS, while Appendix B gives a short introduction
to queuing theory.
x Preface
This book provides a comprehensive introduction to the key concepts of
computer networks in a manner that is easily digestible for a beginner in the
field or undergraduate students. The textbook is primarily intended for major
universities and colleges offering courses on computer networks. It is written
for a one-semester senior-level course on computer networks. It may also
serve as a reference or a quick review of fundamentals of computer networks
to people in industry. A practicing engineer who needs an overview of com-
puter networks can also benefit. We are grateful for the support of Dr.
Annamalia Annamalai, the department head of the Department of Electrical
and Computer Engineering, and Dr. Pamela Obiomon, the dean of the College
of Engineering at Prairie View A& M University, Prairie View, Texas.
Prairie View, TX, USA Matthew N. O. Sadiku
Cajetan M. Akujuobi
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 What Are Computer Networks? . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Short History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.4 Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Digital Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2 Transmission Media . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2.1 Guided Media. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2.2 Unguided Media. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.3 Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.3.1 Summary of Digital Signal Encoding Formats . . . . . . 13
2.4 Bit/Byte Stuffing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.5 Multiplexing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.6 Switching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3 Network Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.2 OSI Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.2.1 The Physical Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.2.2 The Data Link Layer . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.2.3 The Network Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.2.4 The Transport Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.2.5 Session Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.2.6 Presentation Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.2.7 Application Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.3 TCP/IP Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.3.1 Physical Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.3.2 Network Interface Layer . . . . . . . . . . . . . . . . . . . . . . . 23
3.3.3 Internet Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.3.4 Transport Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.3.5 Application Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.4 Application I: Internetworking Devices . . . . . . . . . . . . . . . . . . 27
3.4.1 Repeaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.4.2 Hubs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.4.3 Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.4.4 Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
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