brown_mit7_ch03

Report
MANAGING INFORMATION TECHNOLOGY
7th EDITION
CHAPTER 3
TELECOMMUNICATIONS AND NETWORKING
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PART 1: IT BUILDING BLOCKS
Building Blocks of Information Technology
Hardware
Software
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Network
Data
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NETWORKING AND TELECOMMUNICATIONS
.
NETWORKING:
The electronic linking of geographically dispersed devices
TELECOMMUNICATIONS:
Communications at a distance, including voice and data
- Also referred to as: data communications, datacom,
teleprocessing, telecom, and networking
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OVERVIEW OF TELECOMMUNICATIONS AND
NETWORKING
• Telecommunications and networking have become
increasingly important to businesses because of
distributed processing and globalization
Early 1990s prediction came true:
“ …networks will change everything"
- Paul Saffo
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THE TELECOMMUNICATIONS INDUSTRY
Three Major Segments of Telecom Industry:
• Carriers who own or lease physical plant & sell the
service of communications transmission
• Equipment vendors who manufacture and sell
telecommunications equipment
• Service providers who operate and deliver network
services or provide access to or deliver services via the
Internet
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THE TELECOMMUNICATIONS INDUSTRY
Example: AT&T
• One of largest carriers in U.S. industry
• In 1984, AT&T split into several companies as a result of a
US Department of Justice antitrust lawsuit
• Breakup of AT&T led to greater innovation through
competition
• But recent trend has been consolidation in the industry
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REASONS FOR NETWORKING
Five primary reasons for networking
1.
2.
3.
4.
5.
Sharing of technology resources
Sharing of data
Distributed data processing and client/server systems
Enhanced communications
Marketing outreach
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REASONS FOR NETWORKING
1. Sharing of technology resources:
• Prior to networking capabilities, computers could not even share
printers….
• Today, PCs share software, mainframes share storage devices, etc.
2. Sharing of data:
• Enables retrieval of data stored on other nodes in the network
• Allows efficient transactions between businesses, their suppliers,
and their customers, based on up-to-date data
• Some businesses share many terabytes of data per day
• Sharing of data via Internet users
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REASONS FOR NETWORKING
3. Distributed data processing and client/server systems:
Distributed data processing
• Information processing that uses multiple computers at multiple
sites that are tied together through telecommunication lines
Client/server systems
• A type of distributed system in which the processing power is
distributed between a central server and a number of client
computers
Client
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Transfer of Data
Server
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REASONS FOR NETWORKING
4. Enhanced communications:
• Telecommunication networks provide the ability to communicate
through Email, Bulletin Boards, Blogs, Instant Messaging, Wikis,
Social network sites, Videoconferencing
• Links between organizations can lead to strategic alliances
o SABRE airline reservation system
o Electronic data interchange (EDI)
5. Marketing outreach:
• Sharing data via the Internet with consumers = an important
marketing and sales channel
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FUNCTIONS OF A TELECOMMUNICATIONS NETWORK
• A telecommunications network is more than a series of
wires or wireless signals…
Table 3.1
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ANALOG AND DIGITAL SIGNALS
• Analog Signals
A signal in which some physical property continuously varies
across time
• Digital Signals
A signal that is not a continuous function of time, but rather
a series of discrete values that represent ones and zeros
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ANALOG AND DIGITAL SIGNALS
• Representation of digital and analog signals
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ANALOG AND DIGITAL SIGNALS
• Digital computer data does not naturally mesh with analog
transmission; it must be converted from ones and zeros to
analog signals
• Solutions:
• Modem (Modulator/Demodulator)
• Digital networks
• Advantages of lower error rates and higher speeds
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TYPES OF TRANSMISSION LINES
 Private (dedicated physical lines)
• Advantage:
- Ensures quality of transmission
• Disadvantage:
- Costly
 Switched (such as public telephone network)
• Advantage:
- Less costly
• Disadvantages:
- Message may take many different routes
- Quality of transmission may degrade
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TYPES OF TRANSMISSION LINES
• Simplex
Data can only travel in one direction
• Half Duplex
Data can travel in both directions, but not simultaneously
• Full Duplex
Data can travel in both directions at once
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TRANSMISSION MEDIA
Twisted Pair
• Literally, wires that are twisted to reduce interference
• Can be shielded (STP) or unshielded (UTP), but the most
commonly used is UTP
• Medium used for public telephone networks
• Transmission speeds vary greatly
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TRANSMISSION MEDIA
Coaxial (Coax) Cable
• Baseband
- Inexpensive, designed for digital transmission
• Broadband
- Originally for analog, now used for digital
- Commonly used in television cable
Figure 3.2
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TRANSMISSION MEDIA
 Wireless
• Not truly a transmission medium, but rather a broadcast
technology in which radio signals are sent through the air
• Cordless telephones and cellular telephones now widely used
• Wireless technologies:
• Wireless LANs
• Microwave
– Line of sight
• Satellite
– Long distances
– Line of sight
• RFID
• Bluetooth
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Wireless Cards
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TRANSMISSION MEDIA
Wireless
• Wireless LANs
- Growing in popularity
- Useful when wiring is not possible
- Slower than some wired solutions
- Allow mobile devices to connect to network
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TRANSMISSION MEDIA
Wireless
• Microwave
- Widespread use for several decades
- Line of sight transmission
- Limited to 25-50 mile distances because of curvature of
the earth
- Expensive, but less costly than fiber optic cables
Microwave Tower
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TRANSMISSION MEDIA
Wireless
• Satellite
1. Geostationary Earth Orbit (GEO)
- Remains stationary relative to earth
2. Low Earth Orbit ( LEO)
- 400 to 1000 miles above earth
Figure 3.3
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TRANSMISSION MEDIA
LEO projects beginning in 1990s
• Iridium
-
First major LEO project with 66 satellites
- Faced high operating costs which resulted in bankruptcy
- Mostly military subscribers
• Globalstar
- LEO project with 40 satellites that does not provide global coverage
• Teledesic
- Ambitious project with original plans to launch 840 satellites
- This was later cut to 288 satellites, then 30, and then the program
was cancelled
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TRANSMISSION MEDIA
Wireless
• RFID
- Acronym for Radio Frequency Identification
- An old technology that became popular in business after
Wal-Mart required the use of RFID by some of its
suppliers to improve inventory and supply chain
management
Wal-Mart and RFID
Wal-Mart CIO on RFID
Wal-Mart gets tough with suppliers about RFID
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TRANSMISSION MEDIA
Wireless
• RFID
• Two Broad Types of RFID tags:
- Active – these tags have their own power supply and can
transmit messages continuously, on request, or on a schedule
Cost over $1.00
- Passive – these tags only send a response to an incoming
radio signal
Cost in the $0.08 - $0.20 range
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TRANSMISSION MEDIA
Wireless
• Bluetooth
• Named after Danish King who united Denmark
• Short-range radio technology
• Designed to consume very little electrical power and be
produced at a low cost
• Found in a growing number of devices such as cell phones,
laptops, headsets, keyboards, mice, and home appliances
- Thousands of Bluetooth products in use today
Bluetooth Devices
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TRANSMISSION MEDIA
Fiber Optics
• Light pulses through a thin fiber of glass or silica
• Faster and more reliable than other media
• Large diameter fiber is multimode (multiple light rays at the
same time) while smaller diameter is single mode
• But smaller diameter fiber has larger capacity due to light
rays bouncing less….
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NETWORK ACCESS FOR INDIVIDUALS
• Internet Service Providers (ISPs) sell access to the Internet
• Consumers now have more options including faster broadband connections
- Digital Subscriber Line (DSL) is a connection through a telephone company
- Cable modem is a connection through a cable television company
- Satellite
• With one-way service, individuals must obtain uplink service from another
provider
- Other Wireless access may be through a municipal carrier or a private
company
• Pricing methods for personal Internet access
- Fixed price (usually monthly plans)
- But hotels, airports, cafes, etc. now offer Internet access for short periods of time
- Cost based on usage (data transferred)
- Also offered “free” to customers in various locations
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NETWORK TOPOLOGY
Network topology = configuration or arrangement of the devices
• Bus
- All devices are attached to one cable
- Single-point failure
• Ring
- Similar to bus, but ends are attached
- Not susceptible to single-point failure
• Star
- All nodes are attached to central device
- Susceptible to failure of central device, but easy to
identify cable failure
• Tree
- Similar to the star, but with a hierarchical structure
• Mesh
- Devices link to multiple other devices
- A failure has little impact on the network, but costly
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Figure 3.4
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NETWORK TYPES
Six types:
1.
2.
3.
4.
5.
6.
Computer Telecommunications Networks
Local Area Networks (LANs)
Backbone Networks
Wide Area Networks (WANs)
The Internet
Internet2
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NETWORK TYPES
1. Computer Telecommunications Networks:
•
•
This was the only type of network until the 1980s
Commonly used in mainframe architectures
Figure 3.5
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NETWORK TYPES
2. Local Area Networks (LANs)
- Standards developed by the Institute for Electrical and
Electronic Engineering (IEEE)
IEEE 802 is a family of standards for LANs and metropolitan area networks
- Five types of LANs in common use today – 3 wired, 2 wireless
o Contention Bus (IEEE 802.3)
o Token Bus (IEEE 802.4)
o Token Ring (IEEE 802.5)
o Wi-Fi (IEEE 802.11)
o WiMAX (IEEE 802.16e)
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NETWORK TYPES - LAN
o Contention Bus (IEEE 802.3)
- Developed by Xerox
- Usually called Ethernet after the original Xerox version
- Half-duplex
- All devices must contend to use
• CSMA/CD protocol for collisions
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NETWORK TYPES - LAN
o Token Bus (IEEE 802.4)
- A token (special message) is passed among devices
- Only the device with the token can transmit a message
- Important for Manufacturing Automation Protocol (MAP)
o Token Ring (IEEE 802.5)
- Developed by IBM
- Combination of ring topology with use of tokens (used the
same way as in token bus)
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NETWORK TYPES - LAN
o Wi-Fi (IEEE 802.11)
- Short for Wireless Fidelity
- Most common wireless LAN type today
- Uses a shared Ethernet design
- CSMA/CA Protocol
• Similar to CSMA/CD, but with less collisions
- Commonly used in offices to supplement wired Ethernet
networks and support mobile devices, or in areas where
adding hardwiring is problematic
- Many U.S. cities are offering Wi-Fi networks
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NETWORK TYPES
o WiMAX (802.16e)
- Newest of the network types
- Similar to Wi-Fi, but operates over longer distances and at
higher speeds
- Can use both licensed and non-licensed frequencies
- Clearwire = leading vendor at this time
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NETWORK TYPES
Wireless Local Area Networks: Some Implementation Problems
- More difficult to secure than other network types
- Organizations that offer wireless access to entice customers
have problems with non-customers or unprofitable customers
overusing the network
- Unauthorized wireless use is also problematic in condos and
apartments
Multiple Unsecured Wireless Networks
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NETWORK TYPES
3. Backbone Networks
•
•
Connect LANs
Key to internetworking
Figure 3.8
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BACKBONE NETWORK DEVICES
Hardware devices for backbone (middle-distance) networks
•Hub: Simple device that forwards all messages to every device
attached to it
•Wireless Access Point: Central device that connects wireless LAN to
other networks
•Bridge: Connects two LAN segments and only forwards messages
that need to go to other segment
•Switch: A multiport bridge; connects two or more LAN segments
•Router: Connects two ore more LANs and only forwards messages
that go to the other LAN
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NETWORK TYPES
4. Wide Area Networks (WANs)
• Similar to LANs, but cover greater distances (“long-haul”)
• We will consider the following three general types of WANs
because they each have advantages and disadvantages:
- Switched Circuit
- Dedicated Lines
- Packet-switched
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NETWORK TYPES - WAN
Switched Circuit (or circuit-switched):
•
A single physical path is temporarily created between two nodes for
their exclusive communication
• Most widely available means of implementing a WAN using a switched
circuit connection is to use the ordinary telephone network
• Advantages
- Easy to set up
• Disadvantages
- Low speed
- High error rates
• There are two different pricing schemes available for this service
- Direct Distance Dialing (DDD) - pay for usage
- Wide Area Telephone Service (WATS) - fixed rate
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NETWORK TYPES - WAN
Dedicated Lines:
•
These are permanent channels exclusive to
the business
• Advantages
- High capacity
- Low error rates
• Disadvantages
- Expensive
•
Two different types of dedicated circuits:
- Leased lines are cable, microwave, or fiber
connections
- Satellite circuits are popular for organizations
with many global locations
- SONET lines are high-capacity leased fiber lines
Table 3.3
Wide Area Networks
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NETWORK TYPES - WAN
Packet-switched:
•
•
•
Multiple connections exist simultaneously over the same physical
circuit
Messages are broken up into packets
Businesses use PADs (Packet assembly/disassembly devices) to
connect their networks to a common carrier network
• Advantages
- Efficient use of network
- Can be high capacity
• Disadvantages
- Packets may arrive in different
order or with delay
Figure 3.9
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NETWORK TYPES
5. The Internet
-
Network of networks that use the TCP/IP protocol
Similar to an enormous WAN
733 million hosts as of January 2010
-
Began with ARPANET and NSFNET
• ARPANET (Advanced Research Projects Agency Network)
was created by the US Department of Defense
• NSFNET (National Science Foundation Network) was
created to link supercomputers for research
• Each of these were largescale, packet-switching networks
that led to the creation of the Internet
ARPANET
NSFNET
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NETWORK TYPES
Internet Applications
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NETWORK TYPES
6. Internet2
-
-
Not-for-profit consortium made up of over 200 universities, as
well as industry and government partners, to develop and deploy
advanced network applications and technologies for research and
commercial purposes
Goals
• Create a leading-edge network capability for the national
research community
• Enable revolutionary Internet applications based on a much
higher-performance Internet than we have today
• Ensure the rapid transfer of new network services and
applications to the broader Internet community
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NETWORKING PROTOCOLS
• Network Protocols
– An agreed-upon set of rules or
conventions governing communication
among elements of a network
– Open Systems Interconnection (OSI)
Reference Model
• Skeleton for standards developed by
International Organization for
Standardization (ISO)
• Conceptual framework to understand
how communications in networks
take place
Figure 3.11
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NETWORKING PROTOCOLS
• Transmission Control Protocol/Internet Protocol (TCP/IP)
• Created to link different types of networks (e.g., satellite and
ground packet networks) together into a network of networks
• Has become de facto standard protocol for networking
-TCP is responsible for the reliable and ordered transmission of
messages
- IP is responsible for routing individual packets based on their
individual addresses (IP addresses)
• Roughly corresponds to network and transport layers of OSI
model
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NETWORKNG HAS BECOME CRITICAL TO DO BUSINESS
• Networking and Telecommunications have become necessary
for businesses to function
• Increasing access to the Internet in developing countries due to
new lines being funded by private and public organizations
Impact of cut Internet cables in Middle East - 2008
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COPYRIGHT
All rights reserved. No part of this publication may be reproduced, stored in a retrieval
system, or transmitted, in any form or by any means, electronic, mechanical,
photocopying, recording, or otherwise, without the prior written permission of the
publisher. Printed in the United States of America.
Copyright © 2012 Pearson Education, Inc.
Publishing as Prentice Hall
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