Oleary2012Comp ppt ch09
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Chapter 9
Communications and
Networks
McGraw-Hill
Copyright © 2012 The McGraw-Hill Companies, Inc. All rights
reserved.
mputing Essentials 2012: Making IT Work for You
Introduction
• We live in a truly connected
society.
• Increased connectivity potentially
means increased productivity,
especially in business.
• You will learn more about the
concept of connectivity and
the impact of the wireless
revolution in this chapter.
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mputing Essentials 2012: Making IT Work for You
Communications
• Computer communications is the
process of sharing data, programs, and
information between two or more
computers
• Numerous applications depend on
communication systems, including
–
–
–
–
–
Instant messaging
Internet telephone
Electronic commerce
Global positioning systems (GPS)
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mputing Essentials 2012: Making IT Work for You
Communications Today
• Connectivity uses computer
networks to link people and
resources
• The Wireless Revolution
– Single most dramatic change in
connectivity and communications
has been widespread use of mobile
telephones with wireless Internet
connectivity
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mputing Essentials 2012: Making IT Work for You
Communication
Systems
• Four basic elements
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–
–
–
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Sending and receiving devices
Communication channel
Connection devices
Data transmission specifications
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mputing Essentials 2012: Making IT Work for You
Communication
Channels
• Communication channels carry
the data from one computer to
another
• Two categories of
communication channels
– Physical connection
– Wireless connection
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mputing Essentials 2012: Making IT Work for You
Physical Connections
• Ethernet cable
(Twisted pair cable)
ã Coaxial cable
ã Fiber-optic cable
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mputing Essentials 2012: Making IT Work for You
Wireless Connections
• Radio frequency (RF)
– Wi-Fi (wireless fidelity)
– Bluetooth (short-range)
– WiMax (extends Wi-Fi)
• Microwave
• Satellite
– Global positioning system (GPS)
• Infrared
– Short distances and line of sight
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Communication Channels
Summary
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mputing Essentials 2012: Making IT Work for You
Connection Device
Signals
• Types of signals
– Analog
– Digital
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mputing Essentials 2012: Making IT Work for You
Connection Devices
• Types of modems
– Telephone modem
– DSL
(digital subscriber line)
– Cable modem
– Wireless modem
(WWAN)
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mputing Essentials 2012: Making IT Work for You
Connection Services
• Dial-Up services
– Uses phone lines
• Leased lines
– Replaced by
optical carrier
(OC) lines
• Digital
subscriber line
(DSL)
– Uses phone lines
– ADSL is most
widely used
type of DSL
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• Cable
– Uses existing TV
cable
– Speeds as fast as DSL
• Satellite connection
services
– Use almost anywhere
– Slower than DSL and
cable modem
• Cellular Services
– Use 3G and 4G
cellular network to
provide wireless
connectivity
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mputing Essentials 2012: Making IT Work for You
Connection Costs and
Speeds
• Typical user connection costs,
bandwidth speeds, and
comparable time required to
download an image in the USA
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Bandwidth
• Measurement of the width or
capacity of the communication
channel
• Categories
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–
–
–
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Voice band (or low bandwidth)
Medium band
Broadband
Baseband
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mputing Essentials 2012: Making IT Work for You
Protocols
• Communication rules for
exchanging data between
computers
• Internet standard: TCP/IP
(Transmission control
protocol/Internet protocol)
– Identification – unique IP address
– Packetization – broken down and
reassembled
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mputing Essentials 2012: Making IT Work for You
Networks
• A computer network is a
communication system that
connects two or more computers
• Allows exchange of information
and resources
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Computer Networks
•
•
•
•
•
•
•
Node
Client
Server
Directory server
Host
Switch
Network interface
cards (NIC)
ã Network operating
systems (NOS)
ã Network administrator
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mputing Essentials 2012: Making IT Work for You
Network Types
• Local area network (LAN)
• Home network
• Wireless LAN (WLAN)
• Metropolitan area
network (MAN)
ã Wide area network
(WAN)
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mputing Essentials 2012: Making IT Work for You
Network Architecture
• Arrangement is called topology
• Types of network topology
– Legacy
• Bus
• Ring
– Current
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ã Star
ã Tree
ã Hybrid
ã Mesh
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mputing Essentials 2012: Making IT Work for You
Bus Network
• Each device is connected to a
common cable, called a bus or
backbone
• All communications travel along
this bus
• There is no host; messages are
passed device-to-device in a
sequence
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