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Chapter 9
Communications and
Networks
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Computing 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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Communications
• Computer communications is the process of
sharing data, programs, and information
between two or more computers
• Numerous applications depend on
communication systems, including
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E-mail
Instant messaging
Internet telephone
Electronic commerce
Global positioning systems (GPS)
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Computing 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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Computing Essentials 2012: Making IT Work for You
Communication Systems
• Four basic elements
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Sending and receiving devices
Communication channel
Connection devices
Data transmission specifications
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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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Physical Connections
• Ethernet cable
(Twisted pair cable)
• Coaxial cable
• Fiber-optic cable
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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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Computing Essentials 2012: Making IT Work for You
Communication Channels Summary
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Connection Device Signals
• Types of signals
– Analog
– Digital
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Computing 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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Connection Services
Computing Essentials 2012: Making IT Work for You
• 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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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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Computing Essentials 2012: Making IT Work for You
Bandwidth
• Measurement of the width or capacity of
the communication channel
• Categories
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Voice band (or low bandwidth)
Medium band
Broadband
Baseband
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Computing 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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Computing 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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Computing Essentials 2012: Making IT Work for You
Computer Networks
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Node
Client
Server
Directory server
Host
Switch
Network interface
cards (NIC)
• Network operating
systems (NOS)
• Network administrator
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Computing Essentials 2012: Making IT Work for You
Network Types
• Local area network (LAN)
• Home network
• Wireless LAN (WLAN)
• Metropolitan area
network (MAN)
• Wide area network
(WAN)
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Network Architecture
• Arrangement is called topology
• Types of network topology
– Legacy
• Bus
• Ring
– Current
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Star
Tree
Hybrid
Mesh
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Computing 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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Computing Essentials 2012: Making IT Work for You
Ring Network
• Each device is connected to two other
devices
• No central file server or computer
• Useful in a decentralized environment
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Computing Essentials 2012: Making IT Work for You
Star Network
• Most widely used network topology for
both homes and large businesses
• Each device connects directly to a central
network switch
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Tree Network
• Each device is connected to a central node,
either directly or through subordinate nodes
• Also known as a hierarchical network
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Hybrid Network
• Combination of different topologies
• Large organizations have a complex
network of smaller networks
– These smaller networks use a variety of
configurations
– When connected together, they form a hybrid
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Mesh Network
• Does not use a specific physical layout, but
requires that each node have more than
one connection to other nodes
• Wireless technologies are frequently used
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Network Topologies
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Network Strategies
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Terminal server network
Client/server network
Peer-to-peer (P2P) network
Distributed processing network
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Terminal Server
Client/Server
Peer-to-Peer
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Computing Essentials 2012: Making IT Work for You
Organizational Networks
• Intranets
– Private network within an organization
– Works like the Internet, where employees use
browsers to access Web sites and Web pages
• Extranets
– Private network that connects organizations
– Works like the Internet, but provides suppliers
and other trusted partners with limited access
to the organization’s networks
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Network Security
• Firewalls
– Combination of hardware and software
– Proxy server provides pass-through access
– Protects against external threats
• Intrusion detection systems (NIDS)
• Virtual private networks (VPN)
– Creates a secure private network connection
between your computer and the organization
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Chapter 9
Communications and Networks
STUDY p274 – 279
VISUAL SUMMARY
MULTIPLE CHOICE Q’s
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KEY TERMS
MATCHING Q’s
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