Chapter 9
Communications and
Networks
9-1
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Competencies (Page 1 of 2)
• Discuss connectivity, the wireless revolution, and
communication systems.
• Describe physical and wireless communications
channels.
• Discuss connection devices, and services including dialup, DSL, cable, satellite/air, and cellular.
• Describe data transmission factors, including bandwidths
and protocols.
9-2
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
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.
9-3
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Communications
The process of sharing data, programs, and
information between two or more computers
9-4
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Communications Today
• Numerous applications depend on communication
systems—E-mail, Instant messaging (IM), Internet
telephone, and Electronic commerce
• Connectivity uses computer networks to link
people and resources
• Going wireless has been the most dramatic
change
9-5
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Communication Systems
• Four basic elements
–
–
–
–
9-6
Sending and receiving devices
Communication channel
Connection devices
Data transmission specifications
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Communication Channels
• Channels carry data from one computer to
another
• Two categories of communication
channels
– Physical connection
– Wireless connection
9-7
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Physical Connections
• Ethernet cable
(Twisted pair cables)
• Coaxial cable
• Fiber-optic cable
Return
9-8
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Wireless Connections
• Radio frequency (RF)
– Wi-Fi (wireless fidelity)
802.11
– Bluetooth
• Microwave
– Line of sight
• Satellite
– GPS
• Infrared
– Short distances
– Line of sight
9-9
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Communication Channels
Summary
9-10
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Connection Device Signals
• Types of signals
– Analog
– Digital
9-11
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Connection Devices
• Types of modems
– Telephone
– DSL
– Cable
– Wireless
Transfer Speeds
9-12
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Connection Services
• Dial-Up services
• Leased lines – T1
– T3 and DS3 have higher capacity
• Digital subscriber line (DSL)
– Uses existing phone lines
– One type widely used is ADSL
• 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
• Cellular Services - use 3G cellular network
9-13
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Typical User Connection Costs
& Speeds
9-14
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Bandwidth
• Measurement of the capacity of the
channel
• Categories
– Voice band also known as low bandwidth
– Medium band
– Broadband
– Baseband
9-15
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Protocols
• Set of communication rules
• Standard for Internet: TCP/IP
(Transmission control protocol/Internet
protocol)
– Identification
– Packetization
9-16
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Networks
• A computer network is a communication
system
• Connects two or more computers
• Allows information exchange
9-17
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Computer Networks
•
•
•
•
Node
Client
Server
Directory server
• Host
• Switch
• Network interface
cards (NIC)
• Network operating
system (NOS)
• Network administrator
9-18
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Network Types
•
•
•
•
•
•
Local area networks
Home networks
Wireless LAN
Personal Area networks
Metropolitan area networks
Wide area networks
LAN
9-19
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Network Architecture
• Arrangement is called topology
• Types of network topology
– Legacy
• Star
• Bus
– Current
•
•
•
•
9-20
Ring
Tree
Hybrid
Mesh
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Star Network
• Smaller computers
linked to a central unit
• Central unit is called
the network switch
• Control is maintained
by routing
Return
9-21
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Bus Network
• Each device handles its own communication
control
• There is no host
• Has a common connecting cable called a
backbone or bus
• All communications travel along this bus
Return
9-22
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Ring Network
• Each device is
connected to two
other devices
• No central file server
or computer
• Useful in a
decentralized
environment
Return
9-23
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Tree Network
• Several computers
linked to a central
node
• Also known as a
hierarchical network
• Useful in centralized
organizations
Return
9-24
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Hybrid Network
• Combination of different
topologies
• Large organizations have
a complex of smaller
networks
– Smaller networks use a
variety of configurations
– Connected together they
form a hybrid
Return
9-25
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Mesh Network
• Newest type of topology
• Does not use a specific
type of layout
• Requires that each node
have more than one
connection to other
nodes
• Wireless technologies
are frequently used
9-26
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Principal Network
Configurations
9-27
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Network Strategies
•
•
•
•
9-28
Terminal
Client/Server
Peer-to-peer
Distributed
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Organizational Networks
• Intranets
– Private network within an organization
– Provides information to
employees
• Extranets
– Private network that connects organizations
– Used to allow suppliers and others access
9-29
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Network Security
• Firewalls
– Hardware & software
– Protects against external threats
• Intrusion detection systems (NIDS)
• Virtual private networks (VPN)
9-30
Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved.