Telecommunications, the Internet, Intranets, and Extranets

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Telecommunications, the Internet, Intranets, and
Extranets

• Chapter 4

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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.

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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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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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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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Elements of a Telecommunications System
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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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Common Wiring and Cabling Types
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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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Carriers and Services

• Common carriers Turk Telecom, ATT
• 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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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 500Kbps-1.5Mbps 20-120 Use standard line Expensive not available ew.
Cable modem 500Kbps-1.5Mbps 20-120 Use existing cable
T1 1.544 Mbps 600-1200 FAST used by corporations EXPENSIVE
Satellite 60-800Kps 30-120 Instead of cable or DSL 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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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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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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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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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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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) Wireless communication for cell phones, handheld computers
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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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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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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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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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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.