Telecommunications, the Internet,
Intranets, and Extranets
Chapter 4
Fundamentals of Information
Systems, Second Edition
1
Learning Objectives
– Define the term telecommunications and
identify and describe the function of the
components of a telecommunications system.
– Identify and briefly describe three basic data
processing strategies, including their
advantages and disadvantages.
Fundamentals of Information
Systems, Second Edition
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Learning Objectives
– Briefly describe how the Internet works,
including alternatives for connecting to it and
the role of Internet service providers.
– Identify and briefly describe common Internet
services.
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Systems, Second Edition
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Learning Objectives
– Describe the World Wide Web and the way it
works, including the use of Web browsers,
search engines, Java, and other Web tools.
– Define the terms intranet and extranet and
discuss how organizations are using them.
– Identify several control and management
issues associated with the use of networks.
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Systems, Second Edition
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Telecommunication
– Electronic transmission of signals for
communications
– Telecommunications device is a hardware
component that allows electronic
communication to occur
– Telecommunications medium carries an
electronic signal and interfaces between a
sending device and a receiving device
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Systems, Second Edition
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Elements of a Telecommunications
System
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Systems, Second Edition
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Media Types (1)
– Twisted-pair wire cable: Twisted pairs of copper wire
• Used in telephone service
• Slow transmission
– Coaxial cable: Conductor wire is insulated
• Faster than twisted-pair
– Fiber-optic cable: Thin strands of glass bound
together
• Uses light beams
• Faster than coaxial cable
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Media Types (2)
– Microwave transmission: High-frequency
radio signal
• Must have unobstructed line of sight between
sender and receiver
• Possible to intervene
– Cellular transmission: Divide area into cells
• Each cell has a mobile telephone subscriber unit
• Possible to intervene
– Infrared transmission: Signals as light waves
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Systems, Second Edition
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Common Wiring and Cabling Types
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Systems, Second Edition
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Common Telecommunications Devices
– Modem: Translates data from digital form into
analog form (for ordinary phones) and back
• MOdulation and DEModulation
– Fax modem: Facsimile device but also a
modem
– Multiplexer: Allow several signals to be
transmitted over the same line
– PBX: Manages both voice and data transfer
• Switching equipment routes phone calls and
messages within the building
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Systems, Second Edition
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Carriers and Services
• Common carriers: Turk Telecom, AT&T
• Switched lines
– Use switching equipment to connect one phone to
another
– Switch: Special purpose circuit that directs messages
in certain directions
• Digital subscriber lines (DSL)
– Use existing lines to transmit signals over 500Kbps
– Faster Internet access
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Systems, Second Edition
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Costs, Advantages, and Disadvantages of
Several Line and Service Types
Line/Service
Speed
Cost per
month
Advantages
Disadvantages
Standard
phone line
56Kbps
$10-40
Broadly
available
Too slow
ISDN
64-128Kbps
$50-150
Faster
Not available
everywhere
DSL
500Kbps1.5Mbps
$20-120
Use standard Expensive; not
line
available ew.
Cable
modem
500Kbps1.5Mbps
$20-120
Use existing
cable
T1
1.544 Mbps
$600-1200 FAST; used by
“”
EXPENSIVE
corporations
Satellite
60-800Kps
$30-120
Instead of
cable or DSL
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Systems, Second Edition
Expensive
installation
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Networks and Distributed Processing
• Computer network - communications media, devices, and software
needed to connect two or more computer systems.
• Centralized processing - processing occurs in a single location or
facility.
• Decentralized processing - processing devices are placed at
various locations.
• Distributed processing - computers are placed at remote locations
but are connected to each other via telecommunications devices.
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Systems, Second Edition
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Terminal-to-Host Connection
• Host computer has the data and the processing
power
• Dumb terminal contacts host computer for jobs
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File Server Connection
• The application and database reside in host
computer.
• Files transferred as a whole and processed by
the user
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Client/Server Connection
• Servers have special functionalities (database
server, program execution, etc.)
• Clients request services from servers
• Clients process service results
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Systems, Second Edition
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Network Types
• Local area network (LAN)
– Same geographic area
– Wired into office buildings (unshielded twisted-pair)
• Wide area network (WAN)
– Microwave and satellite transmission
– Long-distance calls
• International network
– Transborder data flow
– International laws
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Systems, Second Edition
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A Typical LAN
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A Wide Area Network
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Connecting Computing Devices Using a Home
Network
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Systems, Second Edition
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Communications Software and
Protocols
• Communications software - provides a number of
important functions in a network
• Network operating system - controls the computer
systems and devices on a network and allows them to
communicate with each other
• Network management software - a manager can
monitor the use of individual computers and shared
hardware
• Communications protocol - rules and standards that
make communications possible
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Systems, Second Edition
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Common Communications Protocols
Protocol
Description
Open Systems Interconnection
(OSI)
Divides data communication into
seven layers for maintenance
Transport control
protocol/Internet Protocol
(TCP/IP)
Primary communication protocol of
the Internet
Ethernet
Used in LANs
Asynchronous transfer mode
(ATM)
Organizes data into 53-byte cells for
fast transmission
802.11a
Supports wireless ATM devices
Bluetooth
Wireless communication for cell
phones, handheld computers
802.11b (Wi-fi)
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Use and Functioning of the
Internet
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Routing Messages Over the Internet
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How the Internet Works
• Internet Protocol (IP): Set of rules to pass
packets from one computer to another
• Transport Control Protocol (TCP): Set of
rules to establish and break connections
• Internet Protocol Address: Unique address
for each computer on the Internet
• Static vs. dynamic
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U.S. Top-Level Domain Affiliations
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Three Ways to Access the Internet
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Internet Service Providers
• Organizations that provide access to the
Internet
• Choose based on price, reliability, other
features (e-mail address)
• Examples: Superonline, E-kolay
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Internet and
Telecommunications Services
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Summary of Internet Services (1)
•
•
•
•
•
•
•
E-mail
Instant messaging
Telnet/SSH
FTP
Chat rooms
Internet phone
Internet video conferencing
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Summary of Internet Services (2)
•
•
•
•
Shop on the Web:
Auctions: http://www.gittigidiyor.com/
Distance learning
Music, radio on the Internet
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Systems, Second Edition
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Common Abbreviations Used in Personal
E-Mail
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Two Approaches to Electronic Data
Interchange
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Public Network and Specialized Services
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The World Wide Web
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The World Wide Web
An Internet service comprising tens of thousands
of independently owned computers that work
together as one.
– Home page: Cover page with text and graphics
– Hypertext markup language (HTML): Standard
language to describe Web pages
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Systems, Second Edition
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Several Interesting Web Sites
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Sample HTML
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Search Engine
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Intranets and Extranets
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Intranets and Extranets
• Intranet – an internal corporate network built using
Internet and WWW standards and products
• Extranet - a network that links selected resources of the
intranet of a company with its customers, suppliers, or
other business partners
• Virtual private network - a secure connection between
two points across the Internet
• Firewall - a device that sits between your internal
network and the outside Internet
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Systems, Second Edition
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Summary of Internet, Intranet, and
Extranet Users
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Virtual Private Network
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Net Issues
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Privacy and Security
• Cookie: Text that is put on user computer to
track Web site usage
• Cryptography: Converting a message into a
secret code and then back into the message
• Encryption
• Digital Signature: Who sent the message, did
the message change on the way?
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Cryptography
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Systems, Second Edition
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Summary
• Networks - used to share hardware, programs,
and databases across the organization.
• Internet - transmits data from one computer
(called a host) to another.
• The Web - a collection of tens of thousands of
independently owned computers that work
together as one in an Internet service.
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Systems, Second Edition
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