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5/26/2011
• “The hardest thing to learn in life is which bridges to cross, and which to burn”
Discovering
Computers 2012
Your Interactive Guide
to the Digital World
Communications
Communications
What is needed for successful communications?
What are computer communications?
¾
Process in which two or more computers or devices transfer data,
instructions, and information
Sending
device — initiates
instruction to
transmit data,
instructions or
instructions,
information
Communications
device — connects
the sending device to
the communications
channel
Communications
device — connects
the communications
channel to the
receiving device
Next
Communications
channel — media
on which data,
instructions, or
i f
information
i travell
Receiving
device — accepts
transmission of data,
instructions, or
information
Next
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Uses of Computer Communications
Blogs
Chat rooms
E‐mail
Fax
FTP
Instant messaging
Internet
Newsgroups
g p
RSS
Video conferencing
VoIP
Web
Web 2.0
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Web folders
Uses of Computer Communications
• A cybercafé is a coffeehouse, restaurant, or other location that provides personal computers with Internet access to its customers Wikis
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Uses of Computer Communications
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Uses of Computer Communications
Collaboration and groupware
¾ Collaboration is working
with other users connected
to a server
ƒ
A document management
system provides for storage
and management of a
company’s documents
¾ Groupware is software
that allows people to
work together and share
information
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Next
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Networks
Networks
What is a network?
¾ Collection of
computers and
devices connected
via communications
devices and
transmission
media
• A local area network
(LAN) is a network that connects computers and devices in a limited geographical area
• A wireless LAN (WLAN) is a LAN that uses no physical wires
Page 472 Figures 9‐10 – 9‐11
Next
Discovering Computers 2012: Chapter 9
Networks
Networks
• A metropolitan area network (MAN) connects LANs in a metropolitan area
• A wide area network (WAN) is a network that covers a is a network that covers a
large geographical area
• The design of computers, devices, and media on a network is sometimes called the network architecture
Page 473 Figure 9‐12
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Client/server network
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Pages 473 – 474
Figures 9‐13 – 9‐14
10
Peer‐to‐peer network
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Networks
Networks
What is a star network?
• A network topology refers to the layout of the computers and devices in a communications network
Star network
Pages 475 – 477
Figures 9‐16 – 9‐18
Bus network
¾
Ring network
Discovering Computers 2012: Chapter 9
¾
All devices connect to
a central device (hub
or switch)
All data transferred
from one computer to
another passes
through hub or switch
Next
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Networks
Networks
What is a ring network?
What is a bus network?
¾ All computers and devices connect to central
cable or bus
¾
¾
Next
Cable forms closed
ring, or loop, with all
computers and devices
arranged along ring
Data travels from
device to device
around entire ring, in
one direction
Next
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Networks
Communications Software
• Communications software consists of programs that:
An intranet is an internal network that uses Internet technologies
Page 477
Help users establish a connection to another computer or network
An extranet allows customers or suppliers to access part of its intranet
Discovering Computers 2012: Chapter 9
Manage the transmission of data, instructions, and information
Provide an interface for users to communicate with one another
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Communications Over the Telephone Network
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Communications Over the Telephone Network
• The public switched telephone network (PSTN) is the worldwide telephone system
Dial‐up lines
Dedicated line
ISDN line
DSL
FTTP
T‐carrier line
ATM
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Pages 483 ‐ 485
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Communications Over the Telephone Network
Communications Devices
• A communications device is any type of hardware capable of transmitting data, instructions, and information between a sending device and a receiving device
receiving device
• A dial‐up modem converts signals between analog and digital
Page 483 Figure 9‐24
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Communications Devices
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Communications Devices
• A network card enables a computer or device to access a network
• Available in a variety of styles
• Wireless network cards often have an antenna
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Page 485
• A router connects multiple computers or other routers together and transmits data to its correct destination on a network
• Many are protected by a hardware firewall
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Page 488 Figure 9‐31
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Communications Devices
Home Networks
• A hub or switch connects several devices in a network together
• Types of wired home networks:
Ethernet
Powerline cable
Phoneline
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Communications Channel
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Physical Transmission Media
• The amount of data that can travel over a communications channel sometimes is called the bandwidth
• Latencyy is the time it takes a signal to travel from one location to another on a network
• Transmission media carries one or more signals
• Broadband media transmit multiple signals simultaneously
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Page 492 Figure 9‐35
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Physical Transmission Media
Wireless Transmission Media
Twisted‐pair cable
Fiber‐optic cable
Coaxial cable
Page 493
Figures 9‐36 – 9‐38
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Wireless Transmission Media
Wireless Transmission Media
• Cellular radio is a form of broadcast radio that is used widely for mobile communications
• Microwaves are radio waves that provide a high‐
speed signal transmission
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Wireless Transmission Media
• A communications satellite is a space station that receives microwave signals from an earth‐based station, amplifies it, and broadcasts the signal over a wide area
Discovering
Computers 2012
Your Interactive Guide
to the Digital World
Page 496 Figure 9‐42
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Chapter 9 Complete
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