Download Business Data Communications and Networking

Business Data
Communications and
Networking, 6th ed.
FitzGerald and Dennis
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Copyright © 1999 John Wiley & Sons, Inc.
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Chapter 1
Introduction to Data
Communications
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Objectives
Become familiar with…
 the history of communications and
information systems,
 the applications of data communication
networks,
 the major components of networks,
 the importance of standards,
 three key trends in communications and
networking,
Understand the role of network layers.
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INTRODUCTION
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Why Study Data
Communications?
We have moved into an information society
dominated by computers, data
communications, and highly skilled
individuals...
At no other time in our history, has success
(whether individual, corporate, or national)
depended so heavily on intelligence and
information.
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Why Study Data
Communications?
The key technology of the information age is
communications.
Data communications and networking is a
truly global area of study, both because the
technology enables global communication,
and because new technologies and
applications often emerge from a variety of
countries and spread rapidly around the
world.
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A Brief History of
Communications in the U.S.
 1837
- Samuel Morse exhibited a working
telegraph system.
 1843 - Alexander Bain patented a printing
telegraph.
 1876 - Alexander Graham Bell, invented the
first telephone capable of practical use.
 1879 - first private manual telephone
switchboard
 1880 - first pay telephone
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A Brief History of
Communications in the U.S.
 1892
- Canadian government began
regulating telephone rates.
 1910 - ICC regulated interstate telephone
business.
 1915 - first transcontinental telephone serve
and first transatlantic voice connections.
 1934 - Communications Act transferred
regulation of interstate telephone traffic from
ICC to FCC.
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A Brief History of
Communications in the U.S.
 1947
- transistor invented in Bell Labs
 1951 - first direct long distance dialing
 1962 - first international satellite telephone
call
 1968 - Carterfone court decision allowed
non-Bell equipment to connect to Bell
System Network
 1969 - Picturefone service began
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A Brief History of
Communications in the U.S.
 1970
- permitted MCI to provide limited long
distance service in competition to AT&T.
 1984 - deregulation of AT&T
 1980s - public service of digital networks
 1990s - cellular telephones commonplace
 1996 - U.S. Congress enacted the
Telecommunications Act of 1996
 1997 - International agreement signed by
68 countries to reduce regulation in TC
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markets
A Brief History of
Communications in the U.S.
Telecommunications Competition and
Deregulation Act of 1996
Practically overnight, the local telephone industry
in the U.S. went from a highly regulated and
legally restricted monopoly to open competition.
Local service in the U.S. is now open for
competition.
RBOCs are now permitted to provide long
distance services.
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A Brief History of
Communications in the U.S.
The Internet has been a different story.
Virtually all RBOCs, LECs, and IXCs, have
aggressively entered the Internet market.
Today, there are more than 5000 Internet
Service Providers (ISPs) who provide dial-in
access to the Internet to millions of small
business and home users.
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A Brief History of Information
Systems in the U.S.
 1950s
- computer systems used batch
processing with discrete files.
 1960s
- data communication across
telephone lines became more
commonplace.
 1960s-1970s
- online real-time systems
were developed.
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A Brief History of Information
Systems in the U.S.
 1980s
- widespread adoption of personal
computer.
 1990s - more than 60 percent of all PCs in
the U.S. were networked.
As we move into the new century, the most
important aspect of computing is
networking.
Networks already have had a dramatic impact
on the way business is conducted.
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DATA COMMUNICATIONS
NETWORKS
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Data Communications
 Data
Communications
The movement of computer information from one
point to another by means of electrical or
optical transmission systems.
Such systems are often called data
communications networks.
 Telecommunications
Includes the transmission of voice and video as
well as data.
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Components of a Network
 Server
(or Host computer)
Central computer in the network, storing data or
software that can be accessed by the clients.
 Client
The input/output hardware device at the other
end of a communications circuit.
 Circuit
The pathway through which the messages travel.
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Components of a Network
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Components of a Network
 Peer-to-peer
networks
Do not need a server or host, but are designed to
connect similar computers which share their
data and software with each other.
Microcomputer networks are connected by a
hub and cables (circuit).
A router is used to connect two or more
networks, enabling computers on one
network to communicate with computers on
other networks (e.g. the Internet).
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Types of Networks
Networks can be classified in many different
ways. One of the most common is by
geographic scope:
•
•
•
•
Local Area Networks (LAN)
Backbone Networks (BNs)
Metropolitan Area Networks (MANs)
Wide Area Networks (WANs)
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Types of Networks
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Types of Networks
 Local Area
Networks (LAN)
A group of microcomputers of terminals located
in the same general area and connected by a
common circuit.
Covers a clearly defined small area, such as
within or between a few buildings,
Support data rates of 10 to 100 million bits per
second (Mbps).
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Types of Networks
 Backbone
Network (BN)
A larger, central network connecting several
LANs, other BNs, metropolitan area networks,
and wide area networks.
Typically span up to several miles.
Support data rates from 64 Kbps to 45 Mbps.
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Types of Networks
 Metropolitan Area
Network (MAN)
Connects LANs and BNs located in different
areas to each other and to wide area networks.
Typically span from 3 - 30 miles.
Supports data rates of 100 to 1000 Mbps.
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Types of Networks
 Wide Area
Network (WAN)
Connects BNs and MANs and are usually leased
from inter-exchange carriers.
Typically span hundreds or thousands of miles.
Supports data rates of 28.8 Kbps to 2 Gbps.
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NETWORK MODEL
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Network Model
A method of describing and analyzing data
communications networks, by breaking the
entire set of communications functions into
a series of layers, each of which can be
defined separately.
This allows vendors to develop software and
hardware to provide the functions
separately.
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Networking Model
Open System Interconnection (OSI) Model,
developed in 1984, helped change the face
of network computing.
Other models like TCP/IP have become more
prominent in the design of networks and
network technology.
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Networking Model
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Simplified Network Model
 Application
layer (Layer 4)
The application software used by the network
user, allows the user to define what message
are sent over the network.
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Simplified Network Model
 Network
layer (Layer 3)
Takes the message generated by the application
layer and performs three functions before
passing them to the data link layer.
1. Translates the destination of the message into an
address understood by the network.
2. If multiple routes possible, it decides which routes
to take.
3. Collects message accounting information that can
be used to identify how many messages each user
has sent and to track errors.
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Simplified Network Model
 Data
link layer (Layer 2)
Takes the message generated by the network
layer and performs three functions before
passing the message on the physical layer.
1. It controls the physical layer by deciding when to
transmit messages over the media.
2. It formats the message by indicating where
messages start and end, and which part is the
address. (It may break it into smaller packets).
3. It detects and corrects any errors that have
occurred in the transmission of the message.
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Simplified Network Model
 Physical
layer (Layer 1)
The physical connection between the sender
and receiver.
It transfers a series of electrical, radio, or light
signals through the circuit from sender to
receiver.
It specifies the type of connection, and the
signals that pass through it.
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Network Models
For Communications to be successful, each
layer in one computer must be able to
communicate with its matching layer in the
other computer.
This is accomplished by standards.
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NETWORK STANDARDS
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The Importance of Standards
Standards are necessary in almost every
business and public service entity.
The primary reason for standards is to ensure
that hardware and software produced by
different vendors can work together.
The use of standards makes it much easier to
develop software and hardware that link
different networks because software and
hardware can be developed one layer at a
time.
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The Standards Making
Process
Two types of standards:
• Formal standards are developed by an official
industry or government body.
• Defacto standards emerge in the marketplace
and supported by several vendors, but have no
official standing.
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The Standards Making
Process
Formal standardization process has three stages
1. Specification stage: developing a
nomenclature and identifying the problems to
be addressed.
2. Identification of choices stage: those working
on the standard identify the various solutions
and choose the optimum solution from among
the alternatives.
3. Acceptance, the most difficult stage: defining
the solution and getting recognized industry
leaders to agree on a single, uniform solution
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Telecommunications
Standards Organizations
 International
Organization for Standards
(ISO)
Member of the ITU, makes technical
recommendations about data communications
interfaces.
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Telecommunications
Standards Organizations
 International
Telecommunications Union Telecommunication Standardization Sector
(ITU-TSS)
Technical standard setting organization of the UN
ITU. Formerly called the Consultative
Committee on International Telegraph and
Telephone (CCITT)
Comprised of representatives of over 150 Postal
Telephone and Telegraphs (PTTs), like AT&T,
RBOCs, or common carriers.
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TC Standards Organizations
• American National Standards Institute (ANSI)
• Institute of Electrical and Electronics Engineers
(IEEE)
• Electronic Industries Association (EIA)
• National Institute of Standards and Technology
(NIST)
• National Exchange Carriers Association (NECA)
• Corporation for Open Systems (COS)
• Electronic Data Interchange -(EDI) of Electronic
Data Interchange for Administration Commerce
and Transport (EDIFACT).
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FUTURE TRENDS IN
COMMUNICATIONS AND
NETWORKING
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Future Trends
Between now and the year 2010, data
communications will grow faster and
become more important than computer
processing itself.
There are three major trends driving the
future of communications and networking:
• Pervasive Networking
• The Integration of Voice, Video and Data
• New Information Services
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Pervasive Networking
In the future, communications networks will
be everywhere.
This pervasive networking means that
virtually any computer will be able to
communicate with any other computer in
the world.
This will increase telecommuting in which
employees perform some or all of their work
at home instead of going to the office each
day.
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Pervasive Networking
Cellular telephone networks will begin to
compete directly with the current wired
telephone network.
Pervasive networking will also increase the
use of electronic data interchange (EDI),
the paperless transmission of business
documents between companies.
The Internet has experienced such rapid
growth that it now connects millions of
computers in virtually every country in the
world.
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The Integration of Voice,
Video and Data
The integration of voice and data is largely
complete in wide area networks.
The integration of video into computer
networks has been much slower, partly due
to past legal restrictions, and partly due to
the immense communications needs of
video.
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New Information Services
The World Wide Web has changed the nature
of computing so now that almost anyone
with a computer can be their own publisher.
Never before in the history of the human race
has so much knowledge and information
been available to ordinary citizens.
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End of Chapter 1
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