Discovering Computers Fundamentals 2nd Edition by yaofenji

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									Chapter 8
Communications
and Networks
Chapter 8 Objectives


   Discuss the components required for         Describe various types of lines for
       successful communications           communications over the telephone network

                                                    Describe commonly used
Describe uses of computer communications
                                                    communications devices

                                                 Discuss different ways to set up
  Differentiate among types of networks
                                                        a home network

         Explain the purpose of               Identify various physical and wireless
        communications software                        transmission media




                                                                              Next
  Communications
  What are computer communications?




p. 296 Fig. 8-1                       Next
 Communications
 What is needed for successful communications?

              Sending           Communications            Communications
         device — initiates    device — connects          channel — media
           instruction to     the sending device to        on which data,
           transmit data,     the communications           instructions, or
          instructions, or           channel             information travel
            information


                    Communications              Receiving
                   device — connects        device — accepts
                  the communications      transmission of data,
                     channel to the          instructions, or
                    receiving device           information


p. 296                                                                    Next
 Uses of Computer Communications
  What are some uses of communications technology?


                                                           Instant
         Internet           Web            E-Mail         Messaging

                                                     Internet
              Chat Rooms          Newsgroups
                                                    Telephony
                                                         Fax Machine
                            Web            Video
          FTP                                            or Computer
                           Folders      Conferencing
                                                          Fax/Modem




p. 298                                                          Next
 Uses of Computer Communications
  What are wireless messaging services?

         Text messaging                       Wireless instant
      allows users to send                    messaging allows
        and receive short                      wireless mobile
       text messages on a                    devices to exchange
         smart phone or                           messages
              PDA          Picture messaging
                          allows users to send
                           graphics, pictures,
                           video clips, sound
                          files, and short text
                                 messages
p. 298 - 299                                              Next
     Uses of Computer Communications
     What are public Internet
     access points and
     cybercafés?
               Public Internet access
                point allows wireless
                connection to Internet
                in public location
               Cybercafé is coffee
                house that provides
                computers with
                Internet access
Click to view Web Link,
click Chapter 8, Click Web Link
from left navigation,
then click Hot Spots
below Chapter 8
   p. 300 Fig. 8-4                       Next
     Uses of Computer Communications
     What is a global positioning system (GPS)?

      Step 1.
      GPS satellites orbit                        Step 2.
      Earth. Every                                A GPS receiver
      thousandth of a                             (such as in a car,
      second, each satellite                      a PDA, a watch,
      sends a signal that                         a handheld
      indicates its current                       device, or a
      position to the GPS                         collar)
      server.                                     determines its
                                                  location on Earth
                                                  by analyzing at
                                                  least 3 separate
                                                  satellite signals
                                                  from the 24
                                                  satellites in orbit.

Click to view Web Link,
click Chapter 8, Click Web Link
from left navigation,
then click GPS
below Chapter 8
   p. 301 Fig. 8-5                                   Next
  Uses of Computer Communications

  What are collaboration and
  groupware?
            Collaboration is working
             with other users connected
             to a server
                 Microsoft Office 2003
                  allows collaboration
            Groupware is software
             that allows people
             to share
             information




p. 302 Fig. 8-6                           Next
 Uses of Computer Communications
  What are voice mail and web services?
        Voice mail is voice message
         converted to digital form
        Web services describe
         standardized software that
         enables programmers to
         create applications that
         communicate with other
         remote computers over the
         Internet



p. 302                                    Next
     Networks
     What is a network?
                 Collection of computers and devices connected
                  via communications devices and transmission
                  media
      What is a local area network (LAN)?
                 Network in limited geographical area such
                  as home or office building
                        Metropolitan area network (MAN) connects
                         LANs in city or town

Click to view Web Link,
click Chapter 8, Click Web Link
from left navigation,
then click Local Area Networks
below Chapter 8
   p. 303 - 304                                                     Next
  Networks
  What is a wide area
  network (WAN)?
            Network that covers
             large geographic
             area using many
             types of media
            Internet is world’s
             largest WAN




p. 304 Fig. 8-8                    Next
  Networks
  What is a client/server
  network?
            One or more computers
             act as server and other
             computers, or clients,
             access server




p. 305 Fig. 8-9                        Next
  Networks
  What is a peer-to-peer
  network?
            Simple network
             that connects
             fewer than 10
             computers
            Each computer,
             or peer, has equal
             capabilities




p. 305 Fig. 8-10                  Next
  Networks
  What is Internet peer-to-peer
  (P2P)?
    Enables users to
     connect to each other’s
     hard disks and
     exchange files directly




p. 306 Fig. 8-11                  Next
  Networks
  What is network topology?
          Layout of devices in a network
                  Popular topologies are bus, ring, and star
            Bus network
                  All computers and devices connect to a central cable,
                   or bus




p. 306 Fig. 8-12                                                           Next
  Networks
  What is a ring network?
           Cable forms closed
            ring, or loop, with all
            computers and devices
            arranged along ring
           Data travels from
            device to device
            around entire ring, in
            one direction




p. 307 Fig. 8-13                      Next
  Networks
  What is a star network?
           All devices connect to
            a central device, called
            hub
           All data transferred
            from one computer to
            another passes
            through hub




p. 307 Fig. 8-14                       Next
 Networks
 What is an intranet?

           Internal network that uses Internet technologies


           Makes information accessible to employees


           Typically includes connection to Internet


           Extranet allows customers or suppliers to access
           part of company’s intranet



p. 307                                                        Next
    Networks
    What are Ethernet and token ring?

                           Ethernet technology allows computers to contend
                           for access to network
                               If two computers send data at same time,
                                a collision occurs and computers must send again




                           Token ring technology controls access to network
                           by requiring devices to pass a special signal,
Click to view Web Link,    called token
click Chapter 8, Click
Web Link from left
navigation, then click
Ethernet below Chapter 8
   p. 308                                                                          Next
 Networks
  What are TCP/IP and 802.11?
              TCP/IP (Transmission Control Protocol/Internet
               Protocol) technology transmits data by breaking it up
               into small pieces, or packets
                  Commonly used for Internet transmissions
              802.11 is family of standards for wireless LANs




p. 308 - 309                                                       Next
 Networks
  What is Bluetooth?
        Short-range radio waves transmit
         data between Bluetooth devices




p. 309                                      Next
 Networks
  What are IrDA, RFID, and Wireless Applications
  Protocol (WAP)?
                                    Radio Frequency
                                    Identification (RFID)
                                    uses radio signals to communicate
          IrDA                      with a tag placed in an object
          specification allows
          data to be transferred
          wirelessly via infrared   Wireless Applications
          light waves               Protocol (WAP)
                                    allow wireless mobile devices
                                    to access Internet




p. 309                                                              Next
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                                                        Next
 Communications Software
 What is communications software?

         Programs that help users
         establish connection to
         Internet, other network,
         or another computer        Programs that help users
                                    manage transmission of
                                    data, instructions,
                                    and information
                                                           Programs that provide an
                                                           interface for users to
                                                           communicate with one
                                                           another




p. 310                                                                       Next
  Communications Over the Telephone Network

  What is the public switched
  telephone network (PSTN)?
           Worldwide telephone system that handles voice-
            oriented telephone calls




p. 310 Fig. 8-15                                             Next
 Communications Over the Telephone Network

  What is a dial-up line?
        Temporary connection using telephone line for
         communications
            Costs no more than making regular call
            Computers at any two locations can establish a
             connection using modems and telephone network




p. 311                                                        Next
  Communications Over the Telephone Network

  What is a dedicated line?
             Always-on connection
              between two
              communications
              devices
                  Four types are ISDN
                   line, DSL, T-carrier
                   line, and ATM




p. 311 Fig. 8-16                              Next
 Communications Devices
 What are examples of communications devices?

         Common types are dial-up modems, ISDN and
          DSL modems, cable modems, network cards,
              wireless access points, and routers


                 ISDN and DSL modems send
                  and receive data from ISDN
                         and DSL lines




p. 312                                               Next
     Communications Devices
     What is a dial-up modem?
               Converts digital signals to analog signals and vice versa
               Notebook computers often use PC Card modem




Click to view Web Link,
click Chapter 8, Click Web Link
from left navigation,
then click Dial-Up Modems
below Chapter 8
   p. 313 Fig. 8-18                                                   Next
 Communications Devices
 What are ISDN and DSL modems?


            Communications devices that send and
             receive digital ISDN and DSL signals


             Usually external devices in which one
         end connects to a telephone line and the other
           end connects to a port on the system unit



p. 314                                                Next
  Communications Devices
  What is a cable modem?
            Sends and receives
             data over cable
             television network
            Much faster than dial-
             up modem or ISDN
            Sometimes called a
             broadband modem




p. 314 Fig. 8-19                      Next
  Communications Devices
  What is a wireless modem?
            Allows access to the
             Web wirelessly from
             a notebook
             computer, a PDA, a
             smart phone, or
             other mobile device
            Typically use the
             same waves used by
             cellular telephones



p. 314 Fig. 8-20                    Next
  Communications Devices
  What is a network card?
            Adapter card, PC Card, or compact flash card
             that enables computer or device to access network




p. 315 Fig. 8-21                                             Next
 Communications Devices
 What is a wireless access point?
        Central
         communications
         device that allows
         computers and
         devices to transfer
         data wirelessly among
         themselves or to wired
         network




p. 315                              Next
  Communications Devices
  What is a router?
            Connects computers
             and transmits data
             to correct destination
             on network
            Routers forward data
             on Internet using
             fastest available path




p. 315 Fig. 8-22                      Next
     Home Networks

     What is a home network?
               Multiple computers
                connected in home
               Several types of home
                networks
                       Ethernet — connect
                        computers via cable
                       Powerline cable —
                        use electrical lines in house
                       Phoneline — use telephone lines
                       HomeRF (radio frequency) — wireless
Click to view Web Link,
click Chapter 8, Click Web Link
from left navigation,
then click Home Networks
below Chapter 8
   p. 316 Fig. 8-23                                           Next
 Communications Channel
  What is a channel?
              Transmission media on which data travels in
               communications system

               Transmission media
               are materials capable of
               carrying one or more
               signals                      Bandwidth is amount of
                                            data that can travel
                                            over channel




p. 317 - 318                                                  Next
  Communications Channel
  How is a request sent over the Internet using a
  communications channel?
                                Step 1. The sending device
                                requests information using either
                                a physical transmission media
                                or a wireless transmission media.


                         Step 2. When the request leaves
                         the ISP, it travels over T1 lines,
                         microwave stations, earth-based
                         stations, and communications satellites
                         until it reaches the Internet backbone.



                           Step 3. The request travels over T3
                           lines along the Internet backbone.



                   Step 4. The Request travels over T1 lines
                   until it reaches the destination network server.



p. 318 Fig. 8-24                                                      Next
 Physical Transmission Media
  What is physical transmission media?
        Wire, cable, and other tangible materials used
         to send communications signals




p. 319                                                    Next
 Physical Transmission Media
 What are twisted-pair cable and coaxial cable?
           Twisted-pair cable is used for telephone systems and network cabling
           Coaxial cable is often used for cable television wiring




p. 319 - 320 Figs. 8-25—8-26                                               Next
  Physical Transmission Media
  What is fiber-optic cable?
            Capable of carrying
             significantly more
             data at faster speeds
             than wire cables
            Less susceptible
             to interference
             (noise) and, therefore,
             more secure
            Smaller size (thinner
             and lighter)



p. 320 Fig. 8-27                       Next
 Wireless Transmission Media
 What is wireless transmission media?
        Used when inconvenient, impractical, or impossible to
         install cables
        Includes infrared, broadcast radio, cellular radio,
         microwaves, and communications satellites




p. 320                                                       Next
     Wireless Transmission Media
     What are broadcast radio and cellular radio?
               Broadcast radio distributes radio signals over
                long and short distances
               Cellular radio is form of broadcast radio used
                for mobile communications
                       A cellular telephone is a telephone device that uses
                        high-frequency radio waves to transmit voice and
                        digital data messages


Click to view Web Link,
click Chapter 8, Click Web Link
from left navigation,
then click Cellular
Communications below
Chapter 8
    p. 321                                                                     Next
 Wireless Transmission Media
 What is a microwave station?
        Earth-based reflective
         dish used for microwave communications
        Must transmit in straight line with no
         obstructions




p. 321                                            Next
 Wireless Transmission Media
 What is a communications satellite?
        Space station that receives microwave signals
         from earth-based station, amplifies signals, and
         broadcasts signals back to any number of earth-
         based stations




p. 321                                                      Next
Summary of Communications and Networks




    Communications terminology
        and applications
                                           Various communications
                                        devices, media, and procedures
 How to join computers into a network




Chapter 8 Complete

								
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