CSC 1113 – Introduction to Computers LECTURE NOTES – CHAPTER 7 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 network: 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 campus. 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. III. LOCAL AREA NETWORKS (LANs): LIMITED REACH, FAST 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 work. 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 7.9. 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 organizations. 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 them. 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.