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Computers Are Your Future Chapter 8
Computers Are
Your Future
© 2008 Prentice-Hall, Inc.
Computers Are Your Future Chapter 8
Computers Are Your Future
Chapter 8
Networks: Communicating and
Sharing Resources
© 2008 Prentice-Hall, Inc.
Slide 2
Computers Are Your Future Chapter 8
Network Fundamentals
A computer network
consists of two or more
computers linked together to
exchange data and share
resources.
•LAN – local area network
(small geographic area)
•WAN – wide area network
(large geographic area)
© 2008 Prentice-Hall, Inc.
Slide 3
Computers Are Your Future Chapter 8
Communication Devices
 Convert data into signals.
 Transform data from
analog into digital signals
and back.
 Computers, modems,
routers, switches,
wireless access points,
and network interface
cards are all
communication devices.
© 2008 Prentice-Hall, Inc.
computers
modems
routers
switches
Network
Interface Cards
Slide 4
Computers Are Your Future Chapter 8
Communication Devices
Workstations – computer connected to a network
 Called clients
 Contains a network interface card (NIC)
© 2008 Prentice-Hall, Inc.
Slide 5
Computers Are Your Future Chapter 8
Communication Devices
Routers – connect two or more LANs or WANs
 Can determine the best path to route data.
 LANs often use switches which are similar to routers.
© 2008 Prentice-Hall, Inc.
Slide 6
Computers Are Your Future Chapter 8
Communication Devices
File server
 High capacity, high speed computer
 Large hard drive
 Contains a network operating system (NOS)
© 2008 Prentice-Hall, Inc.
Slide 7
Computers Are Your Future Chapter 8
Network Fundamentals
Network administrators
 Install
 Maintain
 Support
 Interact with users
 Troubleshoot problems
© 2008 Prentice-Hall, Inc.
Slide 8
Computers Are Your Future Chapter 8
Advantages of Networks
 Reduced hardware costs
 Application sharing
 Sharing information
resources
 Centralized data
management
 Connecting people
© 2008 Prentice-Hall, Inc.
Slide 9
Computers Are Your Future Chapter 8
Disadvantages of Networks
 Loss of autonomy
 Lack of privacy
 Security threats
 Loss of productivity
© 2008 Prentice-Hall, Inc.
Slide 10
Computers Are Your Future Chapter 8
Local Area Networks (LANs)
 Network access is controlled by a network administrator.
 Users can access software, data, and peripherals.
 LANs require special hardware and software.
 Computers connected to a LAN are called workstations
or nodes.
 Types of LANs:
• Peer-to-peer
• Client-server
© 2008 Prentice-Hall, Inc.
Slide 11
Computers Are Your Future Chapter 8
LAN Hardware and Software
Networking Hardware
Networking Software
Network interface card
Operating system that
(NIC) – Provides the
connection between the
computer and the network
Inserted into a computer’s
expansion slot
supports networking
(Unix, Linux, Windows,
Mac OS)
Additional system
software
NIC
© 2008 Prentice-Hall, Inc.
Slide 12
Computers Are Your Future Chapter 8
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.
 Peer-to peer is not suited for networks with many
computers.
 Peer-to-peer is easy to set up; example: home
networks.
© 2008 Prentice-Hall, Inc.
Slide 13
Computers Are Your Future Chapter 8
Client-Server Networks
 Typical corporate networks are client-server.
 Client-server requires 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.
© 2008 Prentice-Hall, Inc.
Slide 14
Computers Are Your Future Chapter 8
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.
 Click to see examples.
Bus
Ring
Startopology
topology
•
•
•
•
•
•
All workstations
Called
Contains
a daisy
a hubchain
orare
central
attached
wiring
in a
Every workstation
concentrator
circular
arrangement
is connected to a
single
Easy
A
special
tocable
add
unit
workstations
of data called a
Resolves
token
travels
collisions
aroundthrough
the ring
contention management
Workstations
can only transmit data
Difficult
when
theytopossess
add workstations
a token
© 2008 Prentice-Hall, Inc.
Slide 15
Computers Are Your Future Chapter 8
Protocols
 Protocols
are fixed, formalized standards that specify
how computers can communicate over a network.
A
protocol suite is the total package of protocols that
specify how a network functions.
© 2008 Prentice-Hall, Inc.
Slide 16
Computers Are Your Future Chapter 8
Network Layers
user
layer
physical media
receiving
sending
protocol
user
stack
physical media
 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.
 The protocol stack is the vertical (top to bottom)
arrangement of the layers; each layer is governed by its
own set of protocols.
© 2008 Prentice-Hall, Inc.
Slide 17
Computers Are Your Future Chapter 8
Ethernet Protocol

Ethernet uses a protocol called Carrier Sense Multiple Access/
Collision Detection (CSMA/CD)
 CSMA/CD works as follow:
1.
Sender senses the media for a fixed time
2.
Sender computer place a data unit with fixed size (packet), the
packet contains the address of the receiver plus the data, now
two possibilities
3.
If no other computer were sending at the same time, The
packet will reach the destination, the distention will confirm by
sending an acknowledgement back to the sender. If another
computer was sending at the same time, collision will occur
and both packets will not reach their destinations.
4.
As a result of collision, no acknowledgement is sent to the
sender . The sender in this case will assume the packet has
not reached the distention and resend it again after waiting for
some random time interval.
© 2008 Prentice-Hall, Inc.
Slide 18
Computers Are Your Future Chapter 8
Ethernet Protocol
No collision
© 2008 Prentice-Hall, Inc.
Slide 19
Computers Are Your Future Chapter 8
Ethernet Protocol
C
A
B
A and
C transmit
at athe
same time => Collision
collision avoidance
A and C will
re-transmit
after
random
© 2008 Prentice-Hall, Inc.
Slide 20
Computers Are Your Future Chapter 8
Wi-Fi
 Wireless-fidelity
 Wireless LAN
 Uses a central access point
 Advantages
• Fast (11 Mbps)
• Reliable
• Long range
• Integrates with existing networks
© 2008 Prentice-Hall, Inc.
Slide 21
Computers Are Your Future Chapter 8
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.
© 2008 Prentice-Hall, Inc.
Slide 22
Computers Are Your Future Chapter 8
Backbones
 Backbones,
high-capacity transmission lines, can be
regional, continental, or transcontinental.
 Internet backbones can carry 2.5 gigabits of data per
second.
© 2008 Prentice-Hall, Inc.
Slide 23
Computers Are Your Future Chapter 8
The internet protocol
 The internet protocols collectively called
Transmission Control Protocol/Internet Protocol
TCP/IP
 IP enables direct and immediate contact between one
computer another. A computer can contact another by
dialing the other computer’s IP address.
 TCP defines how the connection is established
between 2 computers
© 2008 Prentice-Hall, Inc.
Slide 24
Computers Are Your Future Chapter 8
TCP/IP Protocol
© 2008 Prentice-Hall, Inc.
Slide 25
Computers Are Your Future Chapter 8
Switching and Routing Techniques
Packet switching
Circuit switching
 Networks create an endto-end circuit between the
sending and receiving
computers.
 Electronic switches
establish and maintain the
connection.
© 2008 Prentice-Hall, Inc.
Outgoing messages are
divided into fixed-size
data units called packets.
Packets are numbered and
addressed to the receiving
computer.
Routers examine the
packets and send them to
their destination.
Slide 26
Computers Are Your Future Chapter 8
Circuit Switching
© 2008 Prentice-Hall, Inc.
Slide 27
Computers Are Your Future Chapter 8
Packet Switching
© 2008 Prentice-Hall, Inc.
Slide 28
Computers Are Your Future Chapter 8
Advantages and Disadvantages of Circuit and
Packet Switching
Advantages
Disadvantages
Circuit switching
Voice and real-time
transmission
No delivery delays
Costly
A direct electrical
connection between the
computers is required
Packet switching
Efficient, less
expensive, and reliable
Will function if part of
the network is down
Delays in receiving
packets
Not ideal for real-time
voice communication
© 2008 Prentice-Hall, Inc.
Slide 29
Computers Are Your Future Chapter 8
WAN Protocols
 X.25
is the oldest packet switching protocol; it is used
by automated teller machines and credit card
authorization devices.
 New protocols designed for digital lines and faster
data transfer rates are:
•
•
Switched Multimegabit Data Service (SMDS)
Asynchronous Transfer Mode (ATM)
© 2008 Prentice-Hall, Inc.
Slide 30
Computers Are Your Future Chapter 8
WAN Applications
LAN-to-LAN
WANs are used to connect
LANs at two or more
geographic locations.
Companies use WANs to
connect their branches to
one network system.
© 2008 Prentice-Hall, Inc.
Transaction Acquisition
Information about
transactions is instantly
relayed to the corporate
headquarters.
Point-of-sale (POS)
terminals relay
transactions to central
computers through WANs.
Slide 31
Computers Are Your Future Chapter 8
Chapter 8 Summary
 Computer networks link two or more computers to
exchange data and share resources.
 Two types of computer networks:
• Local area network (LAN)
• Wide area network (WAN)
 Computer networks:
• Reduce hardware costs
• Enable users to share applications
• Provide a means to pool an organization’s data
• Foster teamwork
 Peer-to-peer uses no file server.
© 2008 Prentice-Hall, Inc.
Slide 32
Computers Are Your Future Chapter 8
Chapter 8 Summary continued
 Network topologies are the physical layout of a LAN.
 LAN topologies include:
• Bus topology
• Star topology
• Ring topology
 Protocols define how devices communicate with each
other.
 Ethernet is the most widely used LAN protocol.
© 2008 Prentice-Hall, Inc.
Slide 33
Computers Are Your Future Chapter 8
Chapter 8 Summary (continued)
Point of presence (POP) is a WAN
connection point.
Circuit switching creates permanent end-toend circuit that is optimal for voice and realtime data.
Packet switching does not require a
permanent switched circuit.
© 2008 Prentice-Hall, Inc.
Slide 34