LECTURE NOTES – CHAPTER 7 by pengxiuhui


									                     CSC 1113 – Introduction to Computers


     I.   INTRODUCING COMPUTER NETWORKS: SYNERGY AT WORK                                   CIYF 7.03
Introduce students to the concept of synergy by expanding upon the examples in the textbook.
The idea that the sum of the parts working together exceeds the same components working alone
is a powerful metaphor.

       A.      Types of Computer Networks: LANs and WANs
          As you begin this section, define computer network and briefly explain each type of
   1. Local Area Network (LAN) uses direct cables, wireless radio, or infrared signals to link
      computers within a small geographic area.
   2. Metropolitan Area Network (MAN) uses high speed fiber-optic lines to connect
      computers within a major urban region.
   3. Wide Area Network (WAN) uses long-distance transmission media to connect
      computers separated by a few miles or thousands of miles. The Internet is a WAN open
      to public use. Public Data Networks (PDNs) are WANs that are leased to business and
      government customers.

       B.      Networking Synergies in a Nutshell
          Summarize the four major gains realized by having a computer network:
   1. Reducing hardware costs. Give examples of various resources which can be shared in a
   network environment, such as printers, scanners, and speedy processors.
   2. Enabling shared applications. Give examples of the network versions of software
   applications, such as Microsoft Office, which are distributed from the file server to each
   user’s workstation.
   3. Building massive information resources. Give examples of the power of a database
   when it is readily accessible and updated in real time.
   4. Connecting people. Define the term groupware and give examples of how shared
   applications such as calendars can benefit organizations.

          Teaching Tip: If your campus is currently using a groupware application such as
          Microsoft Exchange or GroupWise as an administrative tool, take time to demonstrate
          the use of shared calendars, distributed lists, and shared resources.
          Web         Link:         Walla       Walla        College       uses      GroupWise
          (www.wwc.edu/services/is/groupwise/) to share information on the campus. Encourage
          students to visit the site and explore the options available to GroupWise users on the

    II. NETWORK FUNDAMENTALS                                                                 CIYF 7.05
Lay the groundwork for this discussion by categorizing the two basic components of a computer
network: physical media that guide messages to their destination, and standards (protocols) that
specify the form required for those messages to be communicated over the network.
CSC 1113 –Introduction to Computers                                                        Page 2
Chapter 7 Lecture Notes

      A.      Physical Media
        Explain to students that while the physical medium used on a network only impacts
        the speed at which data travels, it is helpful to understand the terms that describe how
        physical media transfer a message to its intended destination.

      B.      Switching and Routing Techniques
        Describe the two basic technologies responsible for routing messages to their correct
        destination: circuit switching and packet switching.
        Class Exercise: Which is best? Create two lists on the board entitled “circuit” and
        “packet.” Ask students to list the pros and cons of each. Ask them to reach a
        conclusion as to which technology is most efficient for a data network and which is
        most efficient for a voice network.
        Teaching Tip: Use a postal analogy to describe how packet switching works. Liken
        the distribution of messages on a network to the mail system. Suppose that a message
        to be sent is like a letter being dropped off at the local post office. The letter would be
        opened and cut into little pieces. Then each piece would be put into a separate
        envelope, addressed to the recipient, and reposted. The postman then collects the mail,
        including our letter which may be in a number of different envelopes. The envelopes
        are taken to the post office and added to all of the other mail to be sorted. Our
        envelopes may end up in different bags, and the bags may be put in different trucks.
        Now our envelopes travel to the destination taking a variety of routes. Eventually all of
        the envelopes (packets) begin arriving at the recipient’s local post office. They are
        progressively collected until all of the envelopes are received. Once all of the
        envelopes are received, the post office opens the envelopes and pieces our message
        back together again. The restored document is then given to the recipient who is then
        able to read it. The local post office is the ISP. The postal system is the carrier. The
        sender is the publisher, and the recipient is the reader.
        Web Link: Encourage students to visit the Web site of Cisco Systems
        (www.cisco.com), the worldwide leader in networking equipment for the Internet.

      C.      Protocols
        Explain to students that a protocol is a set of standards or code of behavior that
        specifies network functions. Refer to the exchange in the text on page 8 that relates
        networking protocols to manners. Compare and contrast proprietary protocols and
        open protocols, and their importance on the growth and success of networking.
        Introduce the term protocol suite as a collection of protocols which dictate the overall
        design of a network, called the network architecture.
        Web Link: The Destinations section discusses Web spiders. To enhance students’
        experience,   encourage     them     to    visit   The     Web      Robots   Pages
        (www.robotstxt.org/wc/robots.html) for more information on related programs.

      D.      Network Layers
        Using the metaphor of a layer cake, explain a protocol stack and how a message
        moves through the stack.
        Teaching Tip: The information covered in this section is fairly technical. Depending
        upon the level of your class, it may not be advisable to go into too much detail on
        network switching and routing techniques because students may feel “information
CSC 1113 –Introduction to Computers                                                     Page 3
Chapter 7 Lecture Notes

         overload.” However, if you have students who already show a fair understanding of the
         networking concept, encourage them to expand their knowledge by delving deeper into
         the topics covered in this section.

   CONNECTIONS                                                                               CIYF 7.10
        Explain that the thing that sets the LAN apart from other types of networks is that it is
        limited in geographic reach to about one mile. Most LANs are located within one
        building. Networks for home use are typically LANs. The speed of LANs continues to
        increase, with technology called Gigabit Ethernet allowing data transfer at the rate of
        1 gigabit per second.

      A.      Networking Hardware: Network Interface Cards (NICs)
         Using Figure 7.5, describe that an NIC (Network Interface Card) is necessary to
         enable a computer to work with a LAN. When an NIC is installed and a computer is
         connected to a LAN, the computer is called a workstation. Any device connected to a
         LAN (including a computer) is called a node. Explain that every node on the LAN has
         its own unique numeric address, and that this addressing scheme is important to
         understand when we learn about the Internet.
         Teaching Tip: If you have an NIC in your box of demonstration hardware, pass it
         around the room so students can see first-hand what one looks like.

      B.      Networking Software
         Explain that each computer on the LAN must have system software installed that
         enables it to “talk” with the other computers on the network. Explain that most modern
         operating systems contain this type of software in their standard installations.
         1.   Peer-to-Peer Networks (P2PNs) are the simplest types of networks in that all
         computers are equal—there is no file server. These simple LANs can be set up by
         using operating system software such as Windows or Mac OS with no additional
         software. These are the easiest LANs to set up, and are often used in the home to
         connect two or three computers together.
         2.    Client/Server Networks are used for connecting many computers together and
         require one or more file servers and a network operating system in addition to the
         operating system on each client computer. Use Figure 7.6 to help describe the
         components of a client/server network.

      C.      Media
         Teaching Tip: If you have a box of hardware samples, be sure to include the various
         types of physical media used in a LAN. Ask the IT department of your local cable
         company for foot-long pieces of twisted pair, cat-5, coaxial cable, and fiber-optic
         cable for demonstration use in your class. You may also want to include an old remote
         control as an example of an infrared device. Since wireless radio transmission
         devices are fairly new, you may not be able to get a physical example. However, use
         what students already know about cell phones to explain how wireless connections
         Teaching Tip: Wireless LANs are on the rise. Engage students in a conversation about
         the possible uses of wireless technology for connecting computers, sharing resources
         and transferring data.
CSC 1113 –Introduction to Computers                                                        Page 4
Chapter 7 Lecture Notes

          Web Link: To gain understanding about the rapid proliferation of wireless LANS,
          encourage students to visit www.hotspot.com for lists of sites where computers
          outfitted with wireless LAN cards can connect to networks around the world.

         D.    LAN Topologies
          Define topology as the physical layout of a local area network.
          Teaching Tip: As with the discussion on switching and routing techniques, this may
          be too detailed for some of your students. If time is short, display graphical
          representations of bus, star, and ring topologies as shown in Figure 7.7 a-c, and
          briefly describe the benefits of each.

         E.    LAN Technologies
          Refer to Figure 7.8 to illustrate discussion on popular LAN technologies. Focus your
          discussion on Ethernet because it is by far the most popular LAN standard.

         F.    LAN Protocols
          Explain that the LAN technologies discussed above provide the physical properties and
          data links for the network’s lower layers. It is the LAN protocols in this section which
          handle transporting of data in the higher layers.
          Teaching Tip: Briefly mention IPX/SPX and NetBEUI (pronounced “net-boo-ee”),
          but reserve most of your discussion for the TCP/IP LAN protocol.
          TCP/IP (Transmission Control Protocol/Internet Protocol) is the core of the
          Internet, but can also be used with a variety of lower-level LAN technologies like
          Ethernet. Mention that a LAN that uses TCP/IP is called an intranet.

   IV.    WIDE AREA NETWORKS (WANs): LONG-HAUL CARRIERS                                  CIYF 7.17
          Ask students to recall that a LAN is limited in geographic reach to about one mile.
          Explain that if you need to link computers separated by two miles or thousands of
          miles, you would use a WAN (Wide Area Network).
          Class Exercise: Be sure students read the Currents section “Sharing Wireless
          Communities.” Engage students in the debate over the ethical question of sharing
          bandwidth as introduced in the article. Beyond ethics, discuss the convenience of
          having wireless access points, or “hotspots,” available throughout the world. Imagine
          traveling through Europe with your laptop configured with a wireless NIC. Anywhere
          you found a hotspot, you could connect to the Internet, check your e-mail, make
          reservations, and upload images from your digital camera. Ask if anyone has had
          experience with a wireless Internet community.

         A.    How WANs Work
          Introduce students to the concept of a WAN by drawing their attention to the
          similarities between WANs and long-distance telephone systems as shown in Figure
          1. Point of Presence (POP) Explain that in order to obtain data to carry, the WAN
          must be accessible from a local connection, much like the telephone in your house
          enables you to connect to telephones all over the world. Connections can be made in a
          variety of ways:
CSC 1113 –Introduction to Computers                                                        Page 5
Chapter 7 Lecture Notes

                Modem: Uses a standard local analog telephone line.
                56Kbps Leased Line: A specially conditioned telephone line that enables
                 continuous, end-to-end communication between two points.
                ISDN Services: Connections using ordinary twisted-pair telephone lines.
                ADSL Services: Connections expected to provide 1Mbps access using
                 ordinary twisted-pair telephone lines.
                T1 Lines: A fast, dedicated connection service that is expensive and usually
                 only used by larger organizations, corporations, and universities.
                PVC (permanent virtual circuit) connections: A new local connection
                 service using a type of packet switching known as frame relay.
        Explain to students that this is just a introduction to the types of connections available,
        and that in Chapter 10 we will discuss this topic in greater detail.
        2. Backbones. Discuss the fact that backbones are the high-capacity transmission lines
        that carry WAN traffic. Some are regional while others are continental or
        transcontinental in scope. The main purpose of a backbone is to carry huge amounts of
        data traffic.

      B.        How WANs Are Organized
        Explain to students that the Internet is the mother of all WANs. Most WAN traffic
        travels over connections leased by backbone providers who charge fees to local
        Internet service providers (ISPs), who in turn sell connections to individuals and
        1. PDN (Public Data Network) is a for-public data communications network that
        assures good security and adequate guaranteed bandwidth for a fee.
        2. VPNs (Virtual Private Networks) are networks that are constructed by using public
        wires to connect nodes. These nodes are not open to the public or to any other users
        and are exclusively leased to a single company, ensuring excellent security.

      C.        WAN Protocols
        Ask students to recall that one of the components of a network is the protocol used for
        communications. Because WANs are networks, they also use protocols. Because this
        chapter uses quite a few acronyms and contains a large amount of technical
        information, it is not important that students remember the names and types of
        protocols commonly used for WANs.

      D.        WAN Applications
        WANs enable companies to use many of the same applications we use on the Internet,
        such as e-mail, conferencing, document exchange, and remote database access.
        Emphasize the concept that the reason for using a company-wide WAN for providing
        these applications rather than the Internet is because WANs can be made more secure.
        1.    LAN-to-LAN Connections: WANs are often used to connect LANs that are
        located in separate geographic locations.
        2.    Transaction Acquisition: Computers such as point-of-sale (POS) terminals
        collect data and relay the information to central computers through WANs.
CSC 1113 –Introduction to Computers                                                         Page 6
Chapter 7 Lecture Notes

         3.  Electronic Data Interchange (EDI): EDI is a set of standards that specify how
         companies communicate information about their financial transactions.
         Class Exercise: Lead students in a discussion about how the use of WANs has made it
         easier for businesses to manage business and meet customer needs. Ask if anyone has
         gone into a retail store for a certain item only to have the item unavailable at that
         location. The salesperson then looks the item up on the company-wide WAN and finds
         the item in question at a store nearby. Are there other examples where a shared
         database can save time and energy tracking down an item? Discuss the possibilities of
         sharing a system-wide database in a university or state library system.
         Class Exercise: Before embarking upon discussion, direct students to read the Impacts
         section entitled “The PARC Mystery: Why Did Xerox Not Take Advantage of Its Own
         Innovations?” Based upon information gained in the article, engage students in a
         discussion about the importance of innovation and research in the development of new
         technology. Where would we be today if short-term marketability drove research?
         What types of research in computer technology are being done today, and which
         companies are at the forefront?

   V.   CHAPTER REVIEW                                                               CIYF 7.26
   Web Link: Refer students to www.prenhall.com/ciyf2004 for a review of the chapter, to
   answer the questions, and to complete the exercises and Web research questions.
   Takeaway Points:
   Ask students to recall the objectives identified at the beginning of this lesson. Tie the initial
   objectives with the essential points that met the objectives.
      Definition: Computer networks link two or more computers so that they can exchange
       data and share resources.
      Objective: List the three main types of computer networks. The three types of computer
       networks are local area networks (LANs), metropolitan area networks (MANs), and wide
       area networks (WANs).
      Objective: Discuss the ways that connecting computers increases the value of an
       organization’s information technology investment. Computer networks can reduce
       hardware costs, enable users to share applications, create the means to pool all of an
       organization’s mission-critical data, and foster teamwork and collaboration.
      Objective: Explain the importance of protocols in a computer network. Computer
       networks require physical media, but their most important component consists of the
       protocols that define how network devices can communicate with each other. A network
       requires many protocols to function smoothly. When a computer sends a message over
       the network, the application hands the message down the protocol stack, where a series of
       protocols prepares the message for transmission through the network. At the other end,
       the message goes up a similar stack.
      Objective: Contrast circuit switching and packet switching networks and explain their
       respective strengths and weaknesses. Circuit switching creates a permanent, end-to-end
       circuit that is optimal for voice and real-time data. Packet switching does not require a
       permanent switched circuit and can funnel more data through a medium with a given data
       transfer capacity. But packet switching introduces slight delays that make the technology
       less than optimal for voice or real-time data.
      Objective: Distinguish between peer-to-peer and client/server LANs. A peer-to-peer
       LAN doesn’t use a file server and is most appropriate for small networks. Client/server
CSC 1113 –Introduction to Computers                                                   Page 7
Chapter 7 Lecture Notes

       networks offer network navigation tools, shared applications, shared databases,
       groupware, and e-mail, but trained technicians are required to configure and maintain
      Objective: Name the most widely used LAN protocol and discuss its benefits. By far the
       most widely used LAN protocol is Ethernet, which is available in 10 or 100 Mbps star
       topology configurations that use hubs and twisted-pair wiring. The newest LAN
       technology, Gigabit Ethernet, can transfer data at the rate of 1,000 Mbps.
      Objective: Identify three business applications of WANs. Businesses use WANs for
       LAN-to-LAN connections, transaction acquisition, and electronic data interchange.

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