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Copyright © 2003 Prentice Hall, Inc
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Copyright
Copyright©©2003
2003Prentice
PrenticeHall,
Hall,Inc
Inc
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COMPUTERS IN YOUR FUTURE 2004
by Bryan Pfaffenberger and Bill Daley
Chapter 7
Networks: Communicating and Sharing Resources
Chapter 7
What You Will Learn
Networks: Communicating and Sharing
Resources
 Major types of computer networks
 How computer connections increase the value of an





organizations information technology investment
The importance of protocols in a computer network
Contrast between circuit switching and packet switching,
as well as their strengths and weaknesses
Differences between peer-to-peer and client/server LANs
The most popular LAN protocol and its benefits
Business applications of WANs
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Introducing Computer Networks
 A computer network consists of two or more
computers linked together to exchange data and
share resources.
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Types of Computer Networks
Local area network (LAN)
 Links computers within a
building or group of
buildings
 Uses direct cables, radio,
or infrared signals
Wide area network
 Links computers
separated by a few miles
or thousands of miles
 Uses long-distance
transmission media
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Metropolitan area network
(MAN)
 Links computers within a
major metropolitan area
 Uses fiber-optic cables
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Networking Synergies in a Nutshell
Reduced hardware
costs
 Users share
equipment
Connected people
 People can work
together without being
at the same location
 Groupware enables
sharing of schedules
and communications
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Shared applications
 Users share software
 File server enables all
users to work with the
same application
program
Building information
resources
 Users create common
pools of data that can
be accessed by
employees
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Network Fundamentals
 Physical media used in networks:
 Cables– Telephone lines, coaxial cable,
microwave, satellites, wireless, and fiber optic
cables connect computers.
 Routers– Devices that examine the data
transmitted and send it to its destination.
 Switches– High speed electronic switches
maintain connections between computers.
 Protocols– Standards that specify how network
components communicate with each other.
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Switching and Routing Techniques
Packet switching
Circuit switching
 Network creates an endto-end circuit between the
sending and receiving
computers
 Same as voice networks
 Suited to voice and realtime videoconferencing
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 Outgoing message is
divided into fixed-size
data units called packets
 Packets are numbered and
addressed to receiving
computer
 Routers examine the
packets and send them to
their destination
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Advantages and Disadvantages of Circuit
and Packet Switching
Advantages
Disadvantages
Circuit switching
Voice and real-time
transmission
No delivery delays
Costly
Need to have direct
electrical connection
between computers to
communicate
Packet switching
Efficient, less
expensive, reliable
Will function if part of
the network is down
Delays in receiving
packets
Not ideal for real-time
voice communication
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Protocols

Protocols are fixed, formalized exchanges that
specify how two dissimilar network components can
establish communication.

Proprietary protocols– Are standards developed and
protected by hardware manufacturers. All hardware
is bought from same manufacturer for the network to
function.

Open protocols– Are nonproprietary protocols. They
are established by independent organizations. Any
hardware supporting the protocols will operate on
the network.

Protocol suite–The total package of protocols that
specify how a network functions.
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Network Architecture

Network architecture is the overall design of a
network.
 The network design is divided into layers, each of
which has a function separate from that of the other
layers.
 Protocol stack– The vertical (top to bottom)
arrangement of the layers. Each layer is governed by
its own set of protocols.
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Local Area Networks (LANs)
 LANs connect computers and peripherals within a
building or group of buildings.
 Users can access software, data, and peripherals.
 LANs require special hardware and software.
 Computers connected to a LAN are called
workstations or nodes.
 Different types of LANs:
 Peer-to-peer
 Client-server
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LAN Hardware and Software
Hardware
 Network interface card
(NIC)– Inserted into a
computer’s expansion slot
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Software
 Operating system that
supports networking
(Unix, Linux, Windows,
Mac OS)
 Additional system
software
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Peer-to-Peer Networks
 All computers on the network are treated as equal.
 There are no file servers.
 Users decide which files and peripherals to share.
 They aren’t suited for networks with many
computers.
 They are easy to set up. Example: Home networks
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Client-Server Networks
 Typical corporate networks are client-server.
 They use various topologies or physical layouts.
 The network requires file servers, networked computers
(clients), and a network operating system (NOS).
 Clients send requests to servers for programs and data,
and to access peripherals.
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Network Media
LANs use a variety of media to carry network signals.
 Twisted pair–Two insulated wires twisted around each
other. The same type of wire as that used for telephones.
 Coaxial cable– Consists of an insulated center wire
surrounded by a layer of braided wire. The same type of
wire as that used for cable TV.
 Fiber-optic cable– A type of fiber glass cable that transmits
data in the form of light impulses. It can carry more data for
longer distances than other wire.
 Infrared– A wireless system that includes a transmitter and
receiver for sending and receiving signals.
 Radio– A wireless system that uses radio signals to send
and receive data.
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LAN Topologies
 The physical layout of a LAN is called its topology.
 Topologies resolve the problem of contention, which
occurs when multiple users try to access the LAN at the
same time.
 Collisions or corrupt data occur when different
computers use the network at the same time.
Bus topology
Star
Ring
topology
 All
Called
Contains
workstations
daisy
a hub
chain
or
attached
central in a
 circular
Every workstation
wiring
concentrator
arrangement
connected
A
tospecial
Easy
a single
to add
unit
bus
workstations
ofcable
data called a
 token
Resolves
travels
collisions
aroundthrough
the ring
 Workstations
contention management
can only
 transmit
Difficult to
data
addwhen
workstations
they
possess a token
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LAN Technologies
LAN protocols are standards that govern the layers of
the protocol stack.
 Lower-layer protocols deal with contention between
computers.
 Lower-layer protocols:
• Ethernet
• LocalTalk
• Token ring
 Higher-layer protocols handle the network functions.
 Higher-layer protocols:
•
•
•
•
AppleTalk
IPX/SPX
NetBeui
TCP/IP
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Wide Area Networks (WANs)
 WANs are similar to long-distance telephone systems.
 They have a local access number called a point of
presence (POP).
 They contain long-distance trunk lines called backbones.
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Point of Presence (POP)
 A point of presence is a WAN network connection
point that enables customers to access the WAN by
making a local telephone call.
 Media used to create a connection from an
organization to a POP include:
 56 Kbps leased line
 ISDN
 ADSL
 T1 line
 Permanent virtual circuit (PVC)
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Backbones

Backbones are high-capacity transmission lines that
carry WAN traffic.
 They are regional, continental, or transcontinental.
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WAN Organization
Internet
 Backbone providers charge
fees to Internet Service
Providers (ISPs).
 ISPs sell subscriptions to
users.
 Not secure
 Not ideal for businesses
Public Data Network (PDN)
 A for-profit data
communications network
 Fees paid on a per-bytetransferred basis
 Good security
 High bandwidth
 Used by corporations, banks and
governments
 Not open to the public
Private Data Network  Most secure type of WAN
 Virtual private network– Lines are leased
to a single company
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WAN Protocols

X.25– Oldest packet switching protocol. It is used by
automated teller machines and credit card
authorization devices.

Switched Multimegabit Data Service (SMDS)–
Designed for digital phone lines. Faster data transfer
rates than X.25.

Asynchronous Transfer Mode (ATM)– Newer type of
protocol. It is designed for digital lines.
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WAN Applications
LAN-to-LAN
 WANs used to connect LANs
at two or more geographic
locations
 Used to connect branches of
a company into one network
system
Transaction Acquisition
 Information about
transaction instantly relayed
to corporate headquarters
 Uses point-of-sale (POS)
terminal as cash register
Electronic Data Interchange (EDI)
 Standards that specify how companies set up
business-to-business transactions
 Speeds ordering, invoicing, and payments
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Chapter 7 Summary
1. Computer networks link two or more computers to
exchange data and share resources.
2. Three types of computer networks:
A. Local area network (LAN)
B. Metropolitan area network (MAN)
C. Wide area network (WAN)
3. Computer networks:
A. Reduce hardware costs
B. Enable users to share applications
C. Provide a means to pool an organization’s data
D. Foster teamwork
4. Computer networks require physical media such as
telephone wire, coaxial cable, infrared, and radio
signals to connect the computers.
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Chapter 7 Summary cont.
5. Network protocols enable the network to function
smoothly.
6. Data is sent through the network by switching and
routing techniques.
7. LAN topologies include:
A. Bus topology
B. Star topology
C. Ring topology
8. Wide area networks are used to link computers
throughout the world.
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THE
END
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