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Communications andNetworks
Chapter 9
9-1 Copyright 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
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Discuss connectivity, the wireless revolution, andcommunication systems.
Describe physical and wireless communicationschannels.
Discuss connection devices, and services including dial-up, DSL, cable, satellite/air, and cellular.
Describe data transmission factors, including bandwidthsand protocols.
Competencies (Page 1 of 2)
9-2 Copyright 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
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Competencies (Page 2 of 2)
Discuss networks and key network terminologies.
Describe different types of networks, including local, home,wireless, personal, metropolitan, and wide area networks.
Describe network architectures, including topologies, and
strategies. Describe organization issues related to Internet
technologies and network security.
9-3Copyright 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
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We live in a truly connected society.
Increased connectivity potentially meansincreased productivity
especially in the businessworld.
You will learn more about theconcept of connectivity andthe impact of the wirelessrevolution in this chapter.
Introduction
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Communications
9-5
The process of sharing data, programs, and
information between two or more computers
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Communications Today
Numerous applications depend on communicationsystemsE-mail, Instant messaging (IM), Internettelephone, and Electronic commerce
Connectivity uses computer networks to link
people and resources Going wireless has been the most dramatic
change
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Communication Systems Four basic elements
Sending and receiving devices
Communication channel
Connection devices
Data transmission specifications
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Channels carry data from one computer to
another
Two categories of communication
channels
Physical connection
Wireless connection
Communication Channels
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Ethernet cable
(Twisted pair cables)
Coaxial cable
Fiber-optic cable
Physical Connections
9-9Return
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Wireless Connections
Radio frequency (RF) Wi-Fi (wireless fidelity)
802.11
Bluetooth
Microwave Line of sight
Satellite
GPS
Infrared Short distances
Line of sight
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Communication ChannelsS
ummary
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Types of signals
Analog
Digital
Connection Device Signals
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Types of modems
Telephone
DSL
Cable
Wireless
Connection Devices
9-13
Transfer Speeds
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D
ial-Up services Leased lines T1 T3 and DS3 have higher capacity
Digital subscriber line (DSL) Uses existing phone lines
One type widely used isADSL Cable
Uses existing TV cable
Provides speeds as fast as DSL at a lower cost
Satellite/air connection services Seven times faster than dial-up
Slower than DSL & cable modem
CellularServices - use 3G cellular network
Connection Services
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Typical User Connection Costs
&S
peeds
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Measurement of the capacity of thechannel
Categories Voice band also known as low bandwidth
Medium band
Broadband
Baseband
Bandwidth
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Set of communication rules
Standard for Internet: TCP/IP(Transmission control protocol/Internet
protocol) Identification
Packetization
Protocols
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A computer network is a communicationsystem
Connects two or more computers
Allows information exchange
Networks
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Computer Networks
Node Client
Server
Directory server
Host Switch
Network interfacecards (NIC)
Network operatingsystem (NOS)
Network administrator
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Local area networks
Home networks
Wireless LAN
Personal Area networks Metropolitan area networks
Wide area networks
Network Types
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LAN
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Arrangement is called topology
Types of network topology
Legacy Star
Bus
Current
Ring Tree
Hybrid
Mesh
Network Architecture
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Star Network
Smaller computerslinked to a central unit
Central unit is called
the network switch
Control is maintainedby routing
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Bus Network Each device handles its own communication
control
There is no host
Has a common connecting cable called abackbone or bus
All communications travel along this bus
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Ring Network
Each device isconnected to twoother devices
No central file serveror computer
Useful in adecentralizedenvironment
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Tree Network
Several computerslinked to a centralnode
Also known as ahierarchical network
Useful in centralizedorganizations
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Return
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Combination of differenttopologies
Large organizations havea complex of smallernetworks
Smaller networks use a
variety of configurations Connected together they
form a hybrid
Hybrid Network
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Newest type of topology
Does not use a specifictype of layout
Requires that each nodehave more than oneconnection to other
nodes Wireless technologies
are frequently used
Mesh Network
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Principal Network
Configurations
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Terminal
Client/Server
Peer-to-peer
Distributed
Network Strategies
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Organizational Networks
Intranets Private network within an organization
Provides information toemployees
Extranets
Private network that connects organizations
Used to allow suppliers and others access
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Network Security
Firewalls
Hardware & software
Protects against external threats
Intrusion detection systems (NIDS)
Virtual private networks (VPN)
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Careers In IT
Network Administrator Manage a companys LAN
andWAN networks
Maintain hardware and
software Diagnose and repairproblems
Candidates usually have abachelors degree incomputer science and
practical experience Annual salary is typically
between $48,500 and$79,000
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Telepresence Lets You Be There
Seeks to create the illusion that you areactually at a remote location
Early implementations mainly focus on anextension of video-conferencing
Someday couldbeyond simplevoice
A Look to the Future
9-33 Copyright 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
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Define and discuss connectivity, thewireless revolution, and communications.
Identify and describe the various physicaland wireless communication channels.
Identify the standard Internet protocol anddiscuss its essential features.
Open-Ended Questions (1 of 2)
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Discuss past and present networktopologies.
Define and discuss four common networkstrategies.
Discussion Questions (2 of 2)
9-35 Copyright 2011 by The McGraw-Hill Companies, Inc. All rights reserved.