Chapter 6 by w3QJ0p6

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									Chapter 6



       Telecommunications &
                  Networks
Communication Model

 Message is communicated via a signal
 Transmission medium (communication channel)
  “carries” the signal



            Encode          Decode




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Telecommunications

 Electronic transmission of signals, e.g., telephone,
  radio, television
 Telecommunication medium: Anything that
  carries an electronic signal & interfaces between a
  sending device & a receiving device
 Data Communications: A subset of
  telecommunications referring to the sending,
  transmission, & receiving of data -- typically
  between computer systems
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Communications & Telecommunications
In human speech, signals are transmitted through the
   air; in telecommunications, signals are transmitted
   through various media




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Elements of Telecommunications




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Types of telecommunication Media (1)
             Twisted Pair
                Insulated copper wire
                Electrical signals
             Coaxial Cable
                Inner wire core surrounded by shielding
                Electrical signals
                Higher transmission speeds than twisted
                 pair
             Fiber-optic Cable
                Extremely thin strands of glass bound
                 together
                Light pulse signals
                Very high transmission speeds
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Types of Telecommunication Media (2)

 Microwave          Satellite




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Types of Telecommunication Media (3)

Cellular transmission signals are transmitted to
  receivers & integrated into the regular network.




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Modems
Translate digital signals to analog for transmission
  over the Public Switched Telephone Network
  (PSTN)




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Carriers & Services (1)
 Common Carriers: Long distance telephone
  companies (AT&T, Sprint)
 Value-Added Carriers: Private telecom systems
  offering enhanced services for a fee
 Switched Lines: Circuits that use switching
  equipment to allow one device to connect to other
  devices (typical phone lines)
 Dedicated Lines: Point-to-point circuits with no
  switching or dialing

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Carriers & Services (2)

 Private Branch Exchange (PBX)
      Telecommunications switching equipment that allows
       users within an organization to share outside lines
      Capable of handling both voice & data traffic
 Integrated Services Digital Network (ISDN)
      Uses existing telecommunications infrastructure to
       simultaneously transmit digital voice, data, & video
      Being phased out in North America (cable & ADSL are
       replacing this service)
 T1 Circuits
      High speed dedicated lines (1.54 Mbps)
      Equivalent to 24 regular voice lines

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Types of Network Configurations

       Ring                       Bus




  Hierarchical
                             Star



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LANs & WANs

 Local Area Network (LAN): Connects computer
  systems & devices in the same geographic area
  (can be ring, bus, hierarchical, star, hybrid)
 Wide Area Network (WAN): Ties together large
  geographic regions using microwave & satellite
  transmission or telephone lines
 International Network (Global Area Network:
  GAN): Links systems between countries

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Types of Computing Connectivity (1)
 Terminal-to-Host                        File Server
      Applications & databases             File server transfers data &
       reside on host mainframe                programs to PCs on the
       computer
                                               network where the PCs
      User accesses applications              perform most processing.
       via a “dumb” terminal


             “Dumb”
             terminal




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Types of Computing Connectivity (2)
 Client/Server
       Applications & databases reside on specialized host
        computers (servers)
       Processing is shared between the host server & the
        client
       Client & server may be different types of computers




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Advantages & Disadvantages of
Client/Server Computing
 Advantages                    Disadvantages
      Reduced costs              Increased costs
      Improved performance       Loss of control
      Increased security         Complex multi-vendor
                                   environment




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Communication Software

 Communications Software: Provides error
  checking, message formatting, communication
  logs, data security/privacy, & translation
  capabilities for networks
 Network Operating System (NOS): Systems
  software that controls the devices on a network &
  allows them to communicate with each other
 Network Management Software: Monitors the
  use of network resources, scans for viruses, &
  ensures compliance with software licenses


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Communication Protocols
 Protocol: Rules that ensure communications
  among different types of computers from multiple
  manufacturers
      Open Systems Interconnection (OSI): Leading
       protocol “model”; comprised of 7 layers
      Transmission Control Protocol/Internet Protocol
       (TCP/IP): Two communication protocols of the
       Internet that work together (rapidly overtaking OSI)
      Systems Network Architecture (SNA): IBM’s
       proprietary communication protocol
      Ethernet: Protocol standard developed for LANs
       using a bus topology
      X.400 & X.500: Standards for message handling
            & network directories
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Bridges, Routers, Gateways, &
Switches
             Bridge: Connects two or more networks
              that use the same protocol at the media
              control sublayer of the data link layer
             Router: Operates at the network level of
              the OSI model with more sophisticated
              addressing software than bridges; can
              determine preferred paths
             Gateway : Operates at or above the OSI
              transport layer & links LANs or networks
              that employ different architectures & use
              dissimilar protocols
             Switch: Switches data to its destination
              by a point-to-point (rather than shared)
              connection

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Telecommunications Applications (1)
 Linking computers & data terminals: Download &
  upload information
 Voice Mail: Enables users to send, receive, &
  save verbal messages, including sending the same
  message to a “group”
 E-mail: Enables users to send, receive, & save
  text messages & attached documents
 Telecommuting: Enables employees to work
  away from the office using PCs & networks to
  communicate electronically
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Telecommunications Applications (2)

 Videoconferencing
     Allows participants to
       conduct long-
       distance meetings
       “face to face” while
       eliminating travel




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Telecommunications Applications (3)

 Electronic Data
  Interchange (EDI)
     Uses networks to allow
          output from one
          organization’s system
          to be processed
          directly as input to
          another organization’s
          systems, without
          human intervention;
          follows standards &
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 Case: Nav Canada, pages 284-285

 Next Class: Chapter 7




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