This Document Contains Chapters 1 to 3 Chapter 1 Introduction to Computer Networks At a Glance Instructor’s Manual Table of Contents • Overview • Objectives • Teaching Tips • Quick Quizzes • Class Discussion Topics • Additional Projects • Additional Resources • Key Terms • • Technical Notes for Hands-On Projects • • Using Virtualization for Hands-On Projects • Lecture Notes Overview • • Chapter 1 offers an introduction to basic computer components and operation. Students learn about the fundamental reasons for networking, as well as how to identify essential network components. They also learn to compare different types of networks. Students learn about servers, their role, and the types of servers that are available. Finally, at the end of the chapter, students are able to describe specialized networks that have recently gained popularity in the world of networking. • Objectives • Describe basic computer components and operation • Explain the fundamentals of network communication • Define common networking terms • Compare different network models • Identify the functions of various network server types • • Describe specialized networks • Teaching Tips An Overview of Computer Concepts • • 1. Provide a brief introduction to networking and why it is so important to have a basic understanding of computer concepts and terminology. Basic Functions of a Computer • • 1. Introduce students to the three basic tasks that all computers perform. • a. Input • b. Output • c. Processing • 2. Give students an idea of where each of the three basic tasks is utilized. For example, a keyboard would be used for input, a screen would be used for output. • • Teaching Tip Students can view a basic breakdown of a computer’s parts and functions at http://www.howstuffworks.com/pc.htm. • Storage Components • • 1. Explain the differences between short-term storage and long-term storage. • • Personal Computer Hardware • • 1. Introduce students to the four major PC components. • • Computer Boot Procedure • • 1. Describe the six steps in the typical computer boot procedure. • • How the Operating System and Hardware Work Together • • 1. Explain the critical services provided by a computer’s OS. • The Fundamentals of Network Communication • • 1. Describe the most basic network as two or more computers connected by some kind of transmission media. • Network Components • • 1. Discuss the three components needed in order to “network” a stand-alone computer. • • Teaching Tip Read an in-depth look at different network media types at http://www.ciscopress.com/articles/article.asp?p=31276. • • Steps of Network Communication • • 1. Basic steps of a user accessing a network resource • Layers of the Network Communication Process • • 1. Explain how the steps of network communication are referred to as layers, and the two models used to describe this process: OSI and TCP/IP. • Teaching Tip • Have students review Simulation 1: Layers of the Communication Process on the book’s CD. • • Teaching Tip Microsoft has an article on the OSI model that helps explain the workings of a layered network: http://support.microsoft.com/kb/103884. • • How Two Computers Communicate on a LAN: Some Details • • 1. Introduce students to idea of a computer’s logical and physical address. • • 2. Use a street address and ZIP code to help explain the difference between a computer’s two addresses. • Teaching Tip • • Have students review Simulation 2: Communication Between Two Computers on the book’s CD. • • • • Quick Quiz 1 • 1. Name the three basic tasks all computers perform: • Answer: Input, Processing, Output. • 2. True or False: Random access memory (RAM) is considered long-term storage. • Answer: False – RAM is considered short-term storage because when power to the computer is turned off, RAM’s contents are gone. • • 3. A computer’s _________ provides a number of critical services, including a user interface, memory management, a file system, multitasking, and the interface to hardware devices. • Answer: operating system (OS) • 4. What is the name given to software that provides the interface between the OS and computer hardware? • Answer: device driver • • 5. What is the physical address assigned to NICs called? • a. Media Address Control • b. Physical Address Control • c. Media Access Control • d. Media Control Access • Answer: Media Access Control • Network Terms Explained • • 1. Explain the importance of learning the “language” of computer networking. • LANs, Internetworks, WANs, and MANs • • 1. Use Figure 1-13 to show the components of a basic network consisting of computers interconnected by a hub. • Teaching Tip For a list of networks and their scopes, see http://en.wikipedia.org/wiki/Computer_network#Types_of_networks_based_on_physical_scope. • • Packets and Frames • • 1. Briefly discuss how data is segmented into packets and then encapsulated into frames for transmission • a. IP addressing information exists in packets • b. MAC addressing added in frames • Clients and Servers • • 1. Explain the different uses of the term client in relation to software / software suites / OS • 2. “Server” can also be ambiguous, cover different definitions in relation to service-based software, server operating systems, and server computers. • Network Models • • 1. Discuss the two major types of network models: peer-to-peer and server-based. • Peer-to-Peer/Workgroup Model • • 1. Peer-to-peer networking model as it relates to client PCs • a. Cover the benefits (cost) of a peer-to-peer network model versus the disadvantages (scalability). • b. Members are all simultaneously servers and clients for whichever resources they may host. • Server/Domain-Based Model • • 1. Explain what it means to be a part of a domain-based network architecture and how it affects user accounts and resource access • a. Advantages in relation to peer-to-peer (centralization, scalability). • b. Services that are related and most likely part of a domain architecture should also be mentioned, such as naming services, or e-mail services. • • Teaching Tip Microsoft Active Directory hasn't always been the only directory services product. Take a look at Novell's older solution, eDirectory: http://www.novell.com/products/edirectory/fsd/comparison.html. • • • Quick Quiz 2 • • 1. An _________ is a networked collection of LANs tied together by devices such as routers. • Answer: internetwork • • 2. What is the more well-known term for chunks of data sent across the network? • Answer: Packet ( Frame is another term that is often used) • • 3. What is the difference between a client and a server, in networking terms? • Answer: A client can be a workstation that requests network resources from a server. A server provides a network service to client computers. • 4. Networks fall into two major types: peer-to-peer and client/server (also called _________). • Answer: server-based • • 5. On a Windows-based peer-to-peer network, all computers are members of a: • a. Domain • b. Workgroup • c. Server network • d. WAN • Answer: Workgroup • • Teaching Tip You can find a comparison of various operating systems at http://en.wikipedia.org/wiki/Comparison_of_operating_system. • • Network Servers • • 1. Discuss common services found on network servers in various sized networks. • Domain Controller/Directory Servers • • 1. Explain the use of directory services to centralize account management and unified resource access. • Teaching Tip Give students the chance to take an in-depth look at Windows Server 2008 Active Directory Domain Services at http://technet.microsoft.com/en-us/library/cc770946%28WS.10%29.aspx. • File and Print Servers • • 1. File and print servers provide a single point of access for storage and printers, as well as additional features such as fault tolerance and load balancing. • Application Servers • • 1. Explain that an application server takes most of the responsibility for processing and data storage, while a client (such as a Web browser) does considerably less work. • a. Common examples of application servers are web-based platforms. • • Communication Servers • • 1. Emphasize the use of communication servers and their ability to service remote users with network resources that would not be available otherwise. • • E-Mail/Fax Servers • • 1. E-mail servers handle and deliver e-mail using a variety of different protocols, while fax servers consolidate incoming and outgoing faxes. • a. SMTP is used to send e-mail • b. POP3 is used to deliver e-mail • • Web Servers • • 1. Web servers host Web pages for access by Web browsers such as Internet Explorer or Firefox. • a. Web servers often provide additional services such as FTP for remote file access. • • Additional Network Services • • 1. Discuss the importance of DNS and DHCP to the functionality of domain services as well as their importance outside of domain environments. • • Server Hardware Requirements • • 1. Emphasize that hardware requirements between client operating systems and server operating systems differ due to the tasks they’re expected to complete. • a. Servers require increasingly more resources depending on load and services provided. • b. Client operating system hardware requirements have increased, while server operating systems have remained relatively the same. • • Specialized Networks • • 1. Discuss various non-computer-centric networks. • • Storage Area Networks • • 1. A SAN provides access to large amounts of networked storage. • a. SANs typically use Fibre Channel or iSCSI. • • Wireless Personal Area Networks • • 1. WPANs help to connect mobile devices to other devices but typically have short range. • a. IEEE 802.15 is the standard for WPANs. • • Quick Quiz 3 • 1. What is the role of an application server? • Answer: Application servers supply the server side of client/server applications, and often the data that goes along with them, to network clients. • 2. What is the role of a communication server? • Answer: Communication servers provide a mechanism for users to access a network’s resources remotely. • • 3. What is the name of the network service that provides name resolution services that allow users to access both local and Internet servers by name rather than address? • Answer: DNS – Domain Name System • 4. A _________ is a short-range networking technology designed to connect personal devices to exchange information. • Answer: wireless personal area network (WPAN) • Class Discussion Topics • 1. Have any of the students installed/configured a LAN before? If so, ask them to briefly discuss their experiences. • • 2. Do students have previous experience configuring servers? If so, ask them to briefly discuss their experiences. • Additional Projects 1. Students can research a list of operating systems (client or server) and detail their hardware requirements. Have them look at Microsoft and non-Microsoft solutions, and compare benefits of either solution in relation to hardware requirements. • 2. Give students the chance to look at network comparisons of small, home peer-to-peer networks versus a larger domain-based server network. Ask them to identify what services they have in common (DHCP, DNS) • Additional Resources • • 1. Computer Networking: • http://en.wikipedia.org/wiki/Computer_network • 2. Linux Networking-Concepts HOWTO: • www.netfilter.org/documentation/HOWTO/networking-concepts-HOWTO.html • 3. Networking Glossary: • www.nextecsystems.com/networking-glossary.html • 4. Client-server: • http://en.wikipedia.org/wiki/Client-server • 5. How Home Networking Works: • http://computer.howstuffworks.com/home-network.htm • Key Terms • application server A computer that supplies the server side of client/server applications, and often the data that goes along with them, to network clients. bus A collection of wires that carry data from one place to another on a computer’s motherboard. client Can be used to describe: an operating system designed mainly to access network resources; a computer’s primary role in a network which is that of running user applications and accessing network resources; software that requests network resources from servers. communication server A computer that provides a mechanism for users to access a network’s resources remotely. core a core is an instance of a processor inside a single CPU chip. See multicore CPU. credentials The username and password or other form of identity used to access a computer. device driver Software that provides the interface between the OS and computer hardware. directory service The software that manages centralized access and security in a server-based network. domain controller A computer running a Windows server OS on which the directory service role called Active Directory is installed. A domain controller maintains a database of user and computer accounts as well as network access policies in a Windows domain. See directory service. domain A collection of users and computers in a server-based network whose accounts are managed by Windows servers called domain controllers. See domain controller. encapsulation The process of adding header and trailer information to chunks of data. file and print server A computer that provide secure centralized file storage and sharing and access to networked printers. frame A packet with the source and destination MAC addresses added to it. In addition, an error-checking code is added to the back end of the packet. Frames are generated by and processed by the network interface. See also packet. header Information added to the front end of a chunk of data so that the data can be properly interpreted and processed by network protocols. internetwork A networked collection of LANs tied together by devices such as routers. See also local area network (LAN). local area network (LAN) A small network limited to a single collection of machines and connected by one or more interconnecting devices in a small geographic area. mail servers A computer that handles sending and receiving e-mail messages for network users. metropolitan area network (MAN) An internetwork that is confined to a geographic region such as a city or county. Uses third-party communication providers to provide connectivity among locations. See also internetwork. multicore CPU A CPU that contains two or more processing cores. See core. multitasking An operating system’s capability to run more than one application or process at the same time. name server A computer that stores the names and addresses of computers on a network allowing other computers to use computer names rather than addresses to communicate with one another. network client software The application or operating system service that can request information stored on another computer. Network Information Service (NIS) A Linux-supported directory service that supports centralized logon. network model Defines how and where resources are shared and how access to these resources is regulated. network protocols The software on a computer that defines the rules and formats a computer must use when sending information across the network. network server software The software that allows a computer to share its resources by fielding requests generated by network clients. packet A chunk of data with source and destination IP addresses (as well as other IP protocol information) added to it. Packets are generated by and processed by the network protocol. peer-to-peer network The network model in which all computers can function as clients or servers as necessary and in which there is no centralized control over network resources. server Can be used to describe: an operating system designed mainly to share network resources; when a computer’s primary role is to give client computers access to network resources; the software that responds to requests for network resources from client computers. server-based network The network model in which server computers take on specialized roles to provide client computers with network services and to provide centralized control over network resources. stand-alone computer A computer that does not have the necessary hardware or software to communicate on a network. storage area network (SAN) A specialized network that uses high-speed networking technologies to provide servers with fast access to large amounts of disk storage. trailer Information added to the back end of a chunk of data so that the data can be properly interpreted and processed by network protocols. Web server A computer running software that allows users to access HTML and other document types using a Web browser. wide area networks (WANs) An internetwork that is geographically dispersed and uses third-party communication providers to provide connectivity among locations. See also internetwork. wireless personal area network (WPAN) A short-range networking technology designed to connect personal devices to exchange information. • Technical Notes for Hands-On Projects • • All projects in this book that use the Sharing and Security option for folders assume that the Use simple file sharing option has been disabled. • • Hands-On Project 1-1: This project requires the NET HELP and NET VIEW utilities. • • Hands-On Project 1-2: This project requires Windows Explorer and the NET VIEW utility. • • Hands-On Project 1-3: This project requires Internet access and a Web browser. • • Hands-On Project 1-4: This project requires Internet access and a Web browser. • • Hands-On Project 1-5: This project assumes students are using Windows XP Professional as the operating system, but the tasks can be accomplished in other operating systems. Students also use a word processor or a simple text editor. • • Using Virtualization for Hands-On Projects • • The following Hands-On Projects/Challenge Labs have been identified as those that students can do using virtual machines rather than physical machines. • • Hands-On Project 1-1 • Hands-On Project 1-2 • Hands-On Project 1-3 • Hands-On Project 1-4 • Hands-On Project 1-5 • • Chapter 2 Network Hardware Essentials At a Glance Instructor’s Manual Table of Contents • Overview • Objectives • Teaching Tips • Quick Quizzes • Class Discussion Topics • Additional Projects • Additional Resources • Key Terms • • Technical Notes for Hands-On Projects • • Using Virtualization for Hands-On Projects • Lecture Notes Overview • • Chapter 1 offers an introduction to the basic operation of network repeaters and hubs. Students learn about the purpose of network switches as well as how to summarize the operation of wireless access points. They will also be able to describe the basic operation of network interface cards. At the end of the chapter, students learn about the very important function of routers in a network. • Objectives • Describe the basic operation of network repeaters and hubs • Explain the purpose of network switches • Summarize the operation of wireless access points • Describe the basic operation of network interface cards • • Explain the function of routers • Teaching Tips Network Repeaters and Hubs • • 1. Describe how repeaters take a weakened signal and repeat it at its original strength. • 2. Show students that many networking devices, such as hubs, switches, and bridges, act as repeaters. • 3. Discuss the purpose of a repeater, or why a device might be used as a repeater. • a. Most often repeaters are used to connect PCs over several hundred feet, where signal would normally degenerate. • 4. Explain the purpose of a hub. • a. Network hubs serve as a connection point to a single network segment. • b. All network devices connected to the hub share the same media and must take turns when using the network. Multiport Repeaters and Hubs • • 1. Explain that a multiport repeater, or hub, will clean a signal as well as regenerate it. • 2. Show that hubs come in a variety of sizes, from 4 ports to 24 ports most commonly • • Hubs and Network Bandwidth • • 1. Explain why when devices are connected to a hub, they must wait their turn to communicate. • a. Because the media must be shared among all connected devices, the average bandwidth available per machine when communicating is much less than whatever speed the hub is rated for. • 2. Discuss the additional cost to bandwidth for the time lost due to network collisions. • a. If two machines try to use the media on the hub at the same time, a collision will occur. All machines must then wait for a period of time before trying again to use the media. • b. Try to demonstrate this with an actual hub and several connected devices generating traffic. • 3. Explain that all devices connected to a hub will see any traffic passed through the hub. • a. While protocol analyzers aren’t covered until much later, this can be demonstrated using Wireshark. Try to connect to a service that passes information in cleartext, such as Telnet, to illustrate how traffic on a hub will work. • 4. You should emphasize the limitations of hubs. • a. Devices on a hub operate in half-duplex mode, meaning that they can only send or receive, not both at the same time. • 5. If you have old hubs available, demonstrate the collision process. Many hubs have an indicator light to show that a collision has occurred or is occurring on the network. • • Have students review Simulation 3—Basic Operation of a Hub on the book’s CD. • Teaching Tip For additional information about shared traffic on hubs, see http://wiki.wireshark.org/HubReference. • • Network Switches • • 1. Explain the benefits of using a switch versus a hub. • Basic Switch Operation • • 1. Illustrate how switches separate connections into individual network segments. In other words, a switch eliminates the possibility of a collision caused by multiple transmitting machines. • a. Use the fact that each port is a separate collision domain as a talking point. • 2. Explain how a switch directs traffic to the correct port by using a MAC address. • a. When a switch powers on, it begins collecting MAC addresses into a switching table, which it then uses as a map to reach specific network devices. • b. MAC addresses are 12 hexadecimal digits long, or 48 bits. • 3. Describe the process of a network transaction with a switch. • a. When a switch receives a frame, it records the sender’s MAC address on the port it was received in the switching table. If the destination MAC address is unknown to the switch, it broadcasts the frame to all connected ports except the original sending port. • b. You can demonstrate this if you have three machines on an isolated network switch, with Wireshark running as you plug all three machines in. • 4. Discuss the advantages inherent in using switches compared to a hub. • a. Switch-based networks do not suffer from the same bandwidth drawbacks as hubs do. Network devices connected to a switch can operate in full-duplex mode, allowing them to transmit while also receiving. • b. Devices connected to a switch do not see each other’s traffic, unlike a hub. They will only see broadcasted traffic and traffic intended for that device. There are a few exceptions to this, namely the situation described in #3-a. A switch will also simply flood all packets to all connected devices if it finds itself out of memory. Under most normal conditions, however, this shouldn’t happen. • • Have students review Simulation 4—Basic Operation of a Switch on the book’s CD. • Teaching Tips • Switches also have the ability to perform more advanced tasks such as link aggregation, or port bonding, to increase link speeds. • • Teaching Tip For a visual guide in explaining how a MAC address is structured, see http://upload.wikimedia.org/wikipedia/commons/9/94/MAC-48_Address.svg. • • • • Quick Quiz 1 • 1. What does a repeater do? • Answer: It receives bit signals generated by NICs and other devices, strengthens them, and then sends them along or repeating them to other parts of the network. • 2. A multiport repeater is often referred to as a _________. • a. Switch • b. Bridge • c. Hub • d. Network Interface Card • Answer: c. hub • • 3. The amount of data that can be transferred on a network during a specific interval is called the _________. • a. Network bandwidth • b. Network speed rating • c. Line speed rating • d. Duplexing speed • Answer: network bandwidth • 4. True or False: A switch operates just like a hub? • Answer: False: Instead of simply regenerating incoming bit signals and repeating them to all other ports, a switch actually reads data in the message, determines which port the destination device is connected to, and forwards the message to only that port • • 5. How long are MAC addresses? • a. 42 bits • b. 16 hexadecimal characters • c. 4 octets • d. 12 hexadecimal characters • Answer: d. 12 hexadecimal characters • Wireless Access Points • • 1. Explain the use of access points as means of wireless distribution. • Basic AP Operation • • 1. Make a comparison of access points to hubs. • a. All wireless clients must share the access media (the air), and multiple machines cannot transmit at the same time. They must all share the bandwidth of the access point. • 2. Explain that although access points are wireless distributors, they still commonly connect to a wired network connection. • 3. Discuss the limitations of wireless, as well as advantages/disadvantages of using a wireless connection. • a. Bandwidth available on a wireless network is often half what is advertised due to overhead in establishing and maintaining the connection. • Teaching Tip Widely available consumer home routers that provide wireless access are actually several devices combined into one, including an access point. It might be helpful to point out some wireless router models as access points. • • Network Interface Cards • • 1. Discuss how network interface cards use different types of media, but all have similar functions and methods of working with operating systems. • NIC Basics • • 1. Describe the process by which a NIC turns a frame into transmittable signals for whatever media type it is made for. • a. In the case of Ethernet, the frame is transmitted electrically. A fiber-optic NIC, however, transmits using light. • 2. Explain why NICs are assigned MAC addresses. • a. These addresses must be unique, or communication on the network no longer works properly. • b. MAC addresses are divided into two parts: the 24-bit organizationally unique identifier (OUI) assigned to the manufacturer and the remaining 24 bits used for a serial number to identify the specific NIC. • 3. Demonstrate the broadcast MAC address. • a. A MAC address of FF:FF:FF:FF:FF:FF is reserved for broadcasts and cannot be used by any NIC. • b. A frame using this broadcast MAC as its destination will be seen by all connected devices. • • Have students review Simulation 5—How a NIC Works on the book’s CD. • Selecting a NIC • • 1. Discuss with students that when selecting a NIC to install in a computer there are a number of factors to consider: • a. What bus type should be used? Several are available, such as PCI and PCIe. Some network cards are available for USB as well. • b. Is the NIC compatible with your operating system? Not all NICs have drivers available for the latest operating systems. • c. How fast should the NIC be? Workstations won’t require a NIC as fast as a server, but faster NICs have become cheap and widely available. • NIC Drivers • 1. Students should learn that NIC drivers in most cases will be automatically installed or already available to modern operating systems. • Wireless NICs • • 1. Discuss the prevalence of wireless NICs in mobile devices. • a. This makes it difficult or impossible to replace NICs on anything but desktop PCs, but eliminates the need to hunt for drivers as well. • 2. Talk about the use of wireless standards and how it affects wireless transmission speeds as well as compatibility. • a. Keep in mind that several wireless standards exist, such as 802.11b and 802.11g. Even though these two standards are backwards compatible, they are not compatible with 802.11a, which uses a different frequency. • b. Another common issue during recent years involved “Draft N” devices that were built by various manufacturers. These devices may or may not work with other “Draft N” devices from other manufacturers. • 3. Discuss what information is needed in order to connect to a wireless network. • a. You must know the service set identifier (SSID). Most wireless routers available for home consumers have default SSIDs configured out of the box, such as “linksys”, “default”, or “2WIRE”. • Teaching Tip • If you have a wireless device, or preferably a workstation/laptop with wireless, try doing a wireless survey around your area. Show students just how prevalent wireless technology is! Nets tumbler is a common tool for doing a wireless survey, and can be found at www.netstumber.com. • • • Quick Quiz 2 • • 1. What is the main difference between a wireless access point and a hub? Answer: Signals don’t travel through a physical medium; they travel through the airwaves as radio signals. • • 2. Before a computer can transmit data to the AP, it must first send a short _________ message to let the AP know it intends to transmit data. • a. Broadcast • b. Request to Send (RTS) • c. Beacon • d. SSID • Answer: b. request to send (RTS) • • 3. What is the name of the address that is part of a NIC? • Answer: Media Access Control or MAC address • 4. A frame with a destination MAC address composed of all binary 1s or FF-FF-FF-FF-FF-FF in hexadecimal is a _________. • a. Unicast frame • b. Anycast frame • c. Multicast frame • d. Broadcast frame • Answer: d. broadcast frame • 5. In order to connect to a wireless network, you need to have the _________. • a. Name of the switch • b. SSID • c. MAC address of the router • d. MAC address of the switch • Answer: b. SSID • Teaching Tip To see more information about the latest 802.11 wireless standard, 802.11n, visit http://en.wikipedia.org/wiki/IEEE_802.11n-2009. • • Routers • • 1. Discuss the role of routers in delivering packets or information to other non-locally connected networks. • • Have students review Simulation 6—Router Operation in a Simple Internetwork on the book’s CD. • Routers Connect LANs • • 1. Explain that in order to communicate between two LANs or networks with different addressing schemes, you need a router. • a. A router is configured to know or find the paths to other networks, either through directly connected interfaces or via other routers. • Teaching Tip An easy way to explain the idea of how routers handle traffic is to use the postal analogy. To see how this works, read http://cs.gmu.edu/cne/itcore/internet/tcpip/tcpip.html. • Routers Create Broadcast Domains • • 1. Detail how and why a router will create broadcast domains. • a. Also discuss the benefits of creating broadcast domains and how broadcast traffic can affect network performance on large scales. • Routers Work with IP Addresses and Routing Tables • • 1. Describe how a router maintains a table of addresses to direct networking traffic. • a. While a switch uses a MAC address to move traffic, a router uses an IP address to route traffic. • b. An IP address is 32 bits long and is separated into four base 256 octets, such as 192.168.1.1. • 2. Briefly discuss what a subnet is and how it works. • a. The network address for a given IP is determined by a subnet mask. Subnet masks, while similar in appearance to IP addresses, use bits to designate the network portion of an address and separate it from the host portion of an address. For example, if the IP address 192.168.1.1 had a subnet mask of 255.255.255.0, then the network address would be 192.168.1.0. • 3. Break down and describe what happens when a router receives a packet addressed to another network • a. First, it checks its routing table for a match. • b. If a match is found for the specific network, the packet is forwarded to the destination. • c. If no match is found, and the router has a default route, the router forwards the packet to the default route. • d. If no match is found and no default route is configured, the packet is dropped. Usually a router will respond to the sender of the packet with a Network Unreachable message. • • Quick Quiz 3 • 1. True or False: Routers are devices that enable multiple LANs to communicate with one another by forwarding packets from one LAN to another. • Answer: True • • 2. The scope of devices to which broadcast frames are forwarded is called a _________. • Answer: broadcast domain • • 3. What is another name for a port on routers? • Answer: Interface • 4. The _________ tells a router where to send a packet with a destination network that can’t be found in the routing table. • Answer: default route • Class Discussion Topics • 1. Discuss the potential reasons for choosing a hub versus a switch, whether it be cost, speed, security, or other. • 2. What might prevent wireless from being used extensively in an enterprise? Ask students to consider how adding a wireless infrastructure might affect a hospital or large credit card company. • Additional Projects 1. If Cisco equipment is available, set up two switches with connections to each other, then connect one PC to each switch. After setting up networking on both PCs, show what the MAC address table of each switch looks like. • Additional Resources • 1. http://en.wikipedia.org/wiki/Broadcast_domain. • 2. http://en.wikipedia.org/wiki/Collision_domain. • Key Terms • access point (AP) A wireless device that serves as the central connection point of a wireless LAN. An AP mediates communication between wireless computers. bandwidth sharing A network design in which the interconnecting devices allow only one connected device to transmit data at a time, thus requiring the devices to share the available bandwidth the interconnecting device provides. broadcast domain The scope of devices to which broadcast frames are forwarded. Router interfaces delimit broadcast domains because they do not forward broadcasts whereas switches and hubs do forward broadcasts. broadcast frame A network message that is intended to be processed by all devices on the LAN. A broadcast frame carries a destination address of FF:FF:FF:FF:FF:FF. clear to send (CTS) A signal generated by an access point in response to a request to send (RTS) signal. A CTS indicates that the computer that sent an RTS may transmit data. See also request to send and access point. dedicated bandwidth A property of switches in which the bandwidth of each port is dedicated to the device or devices connected to the port. This differs from a hub in which the bandwidth of a port is shared among all the devices connected to the hub. default gateway The address configured in a computer’s IP address settings that is set to the address of a router to which the computer can send all packets destined for other networks. default route An entry in a router’s routing table that tells a router where to send a packet with a destination network address that can’t be found in the routing table. full-duplex mode A communication mode in which a device can simultaneously transmit and receive data on the same cable connection. Switches can operate in full-duplex mode but hubs cannot. half-duplex mode A communication mode in which a device can send or receive data but cannot do both simultaneously. Hubs can only operate in half-duplex mode, whereas switches can operate in both half-duplex and full-duplex modes. hub A network device that performs the same function as a repeater but has several ports to connect a number of devices. Sometimes called a multiport repeater. See also repeater. network bandwidth The amount of data that can be transferred on a network during a specific interval, usually measured in bits per second. network interface card (NIC) A device that creates and mediates the connection between a computer and the network medium. promiscuous mode An operational mode of a NIC in which all frames are read and processed rather than only broadcast and unicast frames addressed to the NIC. Protocol analyzer software sets a NIC to promiscuous mode so that all network frames can be read and analyzed. repeater A network device that takes incoming signals and regenerates, or repeats, them to other parts of the network. request to send (RTS) A signal used in wireless networks indicating that a computer has data ready to send on the network. router A device that enables multiple LANs to communicate with one another by forwarding packets from one LAN to another. They also forward packets from one router to another when LANs are separated by multiple routers. Routers have multiple interfaces and each interface communicates with a LAN. service set identifier (SSID) The name assigned to a wireless network so that wireless clients can distinguish between wireless networks when more than one is detected. switch A network device that reads the destination MAC address of incoming frames to determine out which port to forward the frame. switching table A table used by switches that contains MAC address and port pairs. The table is used by the switch to determine which port to forward frames it receives to reach the destination computer. unicast frame A network message that is addressed to only one computer on the LAN. uplink port A designated port on a hub or switch used to connect to another hub or switch without using a crossover cable. • Technical Notes for Hands-On Projects • • Hands-On Project 2-1: This project requires regular classroom computers or virtual machines with a connection to the Internet, or the instructor can provide the Wireshark setup program on a network share. • • Hands-On Project 2-2: This project requires three computers (minimum) with Ethernet NICs installed; 10/100 Mbps or 10/100/1000 NICs are preferable, but 10 Mbps NICs will also work. • • Hands-On Project 2-3: This project requires three computers (minimum) with Ethernet NICs installed; 10/100 Mbps or 10/100/1000 NICs are preferable, but 10 Mbps NICs will also work. Three patch cables and a 10/100 switch, although a single-speed switch or Gigabit switch will also work. • • Hands-On Project 2-4: This project requires three computers (minimum) with Ethernet NICs installed; 10/100 Mbps or 10/100/1000 NICs are preferable, but 10 Mbps NICs will also work. Four patch cables and a crossover cable, 10/100 hubs with uplink switch, and a 10/100 switch. • • Hands-On Project 2-5: This project requires two or more computers with 802.11 wireless NICs installed. One wireless AP or wireless router configured with the service set identifier (SSID, the name for a wireless network) “NetEss.” The 802.11 standard supported doesn’t matter as long as the AP is compatible with the NICs. Windows 7 is the preferred OS, but some steps can be changed to accommodate other OSs. The computers shouldn’t be connected to a hub or switch. • • Hands-On Project 2-6: This project requires a classroom computer; no other tools or equipment are required. Windows 7 is the assumed OS, but this project can also be done in Windows Vista or Windows XP. • • Hands-On Project 2-7: This project requires three workstations, two hubs or switches, a router, and five patch cables. The router can be the same router/AP you used for Hands-On Project 2-5. Assuming you’re using a typical home network router/AP such as a Linksys WRT54GL, the router should be set up so that the WAN interface is assigned the address 192.168.2.1 with subnet mask 255.255.255.0, and the LAN interface is left as the default 192.168.1.1 address. • • Hands-On Project 2-8: This project requires a classroom computer, access to the Internet, and a valid DNS server. • • Challenge Lab 2-1: This project requires a classroom computer with Wireshark installed; the IP address of another classroom computer or device. • • Challenge Lab 2-2: This project requires a computer with Wireshark installed; access to the Internet. • • Using Virtualization for Hands-On Projects • • The following Hands-On Projects/Challenge Labs have been identified as those that students can do using virtual machines rather than physical machines. • • Hands-On Project 2-1 • Hands-On Project 2-6 • Hands-On Project 2-8 • Challenge Lab 2-1 • Challenge Lab 2-2 Chapter 3 Network Topologies and Technologies At a Glance Instructor’s Manual Table of Contents • Overview • Objectives • Teaching Tips • Quick Quizzes • Class Discussion Topics • Additional Projects • Additional Resources • Key Terms • • Technical Notes for Hands-On Projects • • Using Virtualization for Hands-On Projects Lecture Notes Overview • • Chapter 3 offers an introduction to the basic primary physical networking topologies in common use. Students also learn about the primary logical networking topologies. They will be able to describe the major LAN networking technologies found in many networks today. • Objectives • Describe the primary physical networking topologies in common use • Describe the primary logical networking topologies in common use • Describe major LAN networking technologies Teaching Tips Physical Topologies • • 1. Explain the differences between topologies, and weigh the advantages/disadvantages of each one. • 2. Emphasize that a physical topology is different from a logical topology, where the layout of a network could appear completely different. Physical Bus Topology • • 1. Describe the limits of a physical bus topology and how these limits contributed to it becoming a legacy technology. • a. Limit of 30 computers per cable segment • b. Any break in the bus brings down entire network • c. Limited to 10 Mbps half-duplex communication • 2. It is worth mentioning that although this technology is now legacy, the Ethernet standards were born on the physical bus topology. • 3. Students should be told the methods by which signals were passed between machines, especially when only a single cable connected all devices. Signal propagation and signal bounce should be discussed, albeit briefly. • • Physical Star Topology • • 1. Discuss the use of a central device for connecting machines on a network. • 2. Compare the advantages of a physical star topology to the disadvantages of older legacy topologies. • a. Creates a single point of administration • b. Allows for faster network speeds • c. Easily expandable (into extended star) • 3. In contrast to those benefits, be sure to make note that this also creates a central point of failure. While easy to troubleshoot, sometimes having a single point of failure is too big of a risk. • 4. To leverage the single point of failure inherent with plain physical star topologies, students should learn that the most commonly used network topology is now the extended star. • a. The extended star can provide a hierarchical topology structure for easy management • b. Provides easy expandability • c. Does not necessarily eliminate single point of failure concerns, but can be designed for redundancy • • Teaching Tip Physical cabling has come a long way from what was used on some of these legacy topologies. Students may find some of the Thicknet images on http://en.wikipedia.org/wiki/Thicknet interesting. • • Physical Ring Topology • • 1. Explain that a physical ring topology is similar to a bus in cabling structure. • 2. Because of their similarities, physical ring also suffers some of the same disadvantages. • a. A failure of a PC or node on the network brings the whole ring down • 3. Students should be introduced to the idea of a network backbone. Physical ring was most commonly used in connecting LANs to FDDI. Point-to-Point Topology • 1. Describe the point-to-point topology and where it is most prevalent: WANs. • 2. Students should also be aware that point-to-point topologies are also used to bridge wireless networks together when physical cabling isn’t an option. • Teaching Tip • For a simplified look at some of these topologies, point your students to http://learn-networking.com/network-design/a-guide-to-network-topology. • • Mesh Topology • • 1. Discuss the use of mesh topology as a means of redundancy and fault tolerance. • a. Leverage this benefit with the disadvantage of cost, which in a full mesh topology can be exponential with expansion. • b. Partial mesh is a valid solution that helps alleviate cost. • • Quick Quiz 1 • 1. What is the difference between physical topology and logical topology? Answer: The arrangement of cabling and how the cables connect one device to another in a network is considered the network’s physical topology, and the path data travels between computers on a network is considered the network’s logical topology. • 2. True or False: Any break in a physical star topology causes the entire network to go down. Answer: true 3. The physical star topology uses a _________ to interconnect computers in a LAN. • a. Central device • b. Bus cable • c. Access point • d. FDDI backbone Answer: a. Central device, such as a hub or switch • 4. What is the name of the most widely used physical topology in networks today? Answer: extended star • • 5. How many links would you need in a full mesh configuration if you had 4 nodes? • a. 4 • b. 5 • c. 6 • d. 7 • Answer: c. 6 • Logical Topologies • • 1. Focus on the idea that the logical topology, while partially determined by physical topology, may not be similar to the physical topology itself. Mention the following for students: • a. For example, there are physical star topologies that act as a bus logically, such as a star topology that makes use of a hub. • b. Another example is wireless LANs. While the technology may appear to be a star, it is in fact a logical bus. • c. Star topologies can also have a logical ring topology when using a multistation access unit (MAU). • d. Refer students to Figures 3-7 to 3-9 for a visual representation. • • Teaching Tip Students may find http://www.cisco.com/iam/unified/ipt701/ENT/Network_Topology_Diagrams.htm helpful in documenting network topology diagrams. However, students may require a guided look. • • Network Technologies • • 1. Discuss with students what network technology is, namely how it applies to what data link layer protocols are in use. • a. Explain how this might define frame format and which media types are available. • Network Technologies and Media • • 1. Show students a strand of unshielded twisted-pair (UTP) cable. While showing the cable, illustrate the various speeds capable over UTP and discuss the meaning of categories for UTP. • 2. Next, show students some fiber-optic cabling if available to contrast the size difference. Students should learn where fiber is most commonly used. • 3. When detailing coaxial cable, make mention that this is most commonly used for cable-based ISPs, such as Comcast or Cablevision. Briefly explain why coaxial became obsolete for LANs. • 4. Explain to students the difference between baseband and broadband, and give an example of which network technologies use either method of signal transmission. • a. Ethernet uses baseband, while cable TV/modem access uses broadband. • Ethernet Networks • • 1. Detail how Ethernet has scaled to various connection speeds over time, and how it will scale in the future. • 2. Explain that despite how the speed of the interface may change, the underlying Ethernet protocol remains essentially the same. • • Ethernet Addressing • • 1. Review some of the information discussed in Chapter 2 about MAC addressing: why every NIC needs a unique MAC address, and what the broadcast MAC address is used for. • • Ethernet Frames • • 1. Teach students some of the different kinds of frame types, and then explain that frame type has no affect on the attributes of a frame. • 2. Students should know the size of a frame can vary between 64 bytes and 1518 bytes. Discuss the common frame headers and fields. • a. There are exceptions to the 1518 maximum byte frame size, but this generally requires all hardware to be compatible with whatever extension is being used. • • Ethernet Media Access • • 1. Discuss the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) access method, and explain when it is used. • a. Explain how the network responds to collisions with this method, how the method changes when hubs versus switches are used (switches eliminate collisions). • • Teaching Tip • Have students review Simulation 7—The CSMA/CD Process on the book’s CD. • • Collisions and Collision Domains • • 1. Emphasize that collisions are only possible when Ethernet is used on shared media. • a. (FYI) This technically includes the current wireless networks based on 802.11, but the method of access is significantly different; CSMA/CA (Collision Avoidance) attempts to prevent a collision altogether, rather than respond to one after the fact. • b. Explain that although a switch will eliminate collisions on segments it is connected to, this will not provide collision domains to a hub if connected. The hub-connected devices will be on shared media, and a collision will be possible for these devices only. • c. Briefly mention that a collision on a switch is technically possible, but only under certain circumstances that are highly unlikely and almost entirely dependent on configuration. • • Ethernet Error Handling • • 1. Discuss Ethernet’s best effort delivery system. • a. Students should understand that reliable delivery is left to higher-level protocols to ensure. • b. Make students aware that while 1-a means Ethernet makes no effort to retransmit a bad frame (in most cases; see 1-c), it is capable of detecting whether a frame is bad using a Cyclic Redundancy Check (CRC) that is added to the frame trailer. • c. If a collision is detected, Ethernet will retransmit a frame after the backoff period. • • Half-Duplex Versus Full-Duplex Communication • • 1. Describe how half-duplex communication compares to full-duplex. • a. How does half-duplex affect speeds? Access methods? • b. How does full-duplex affect speeds? Access methods? • • Ethernet Standards • • 1. Explain the two methods for expressing Ethernet standards. • a. XBaseY terminology • b. IEEE document number (example: 802.3) • 2. Describe the different Ethernet standards, giving a small amount of time to the legacy standards so that students are aware of Ethernet’s history. • 3. Describe how different standards utilize the same media in different ways. For example, 100BaseT Ethernet dedicates wire pairs to sending and receiving. 1000BaseT Ethernet on the other hand uses all wires for sending and receiving simultaneously. • a. (FYI) This works via several technologies, namely echo cancellation and pulse amplitude modulation (PAM-5) techniques. • b. Some standards also add additional optional features, such as auto-detection for crossover versus straight-through cables. • c. Features such as auto-negotiation should be discussed as well, as incorrect settings for some features of certain protocols will prevent proper network functionality. • d. An example of 3-c, auto-negotiation is required for 1000BaseT to work. • 4. Discuss some of the more common fiber-optic Ethernet standards and their various speeds, benefits, and limitations (namely distance limitations). • 5. Briefly discuss the future of Ethernet speeds, such as the book’s estimate of terabit Ethernet (1000 Gbps) by 2015. • • Quick Quiz 2 • • 1. True of False: Switched Ethernet can be implemented as a bus topology. Answer: False • • 2. _________ is the method a network interface uses to access the medium and send data frames and the structure of these frames. • Answer: Network technology • • 3. When using UTP cabling, what is the maximum cable segment allowed from the computer to a hub or switch? • Answer: 100 Meters • 4. What is the name of the media access method used by Ethernet? • Answer: Carrier Sense Multiple Access with Collision Detection (CSMA/CD) • • 5. What is the standard that describes 10 Gigabit running over four pairs of CAT6A cabling? • a. 10000GBaseTX • b. 10GBaseT • c. 100BaseT • d. 10GBaseFX • Answer: b. 10GBaseT • Teaching Tip Send students to http://en.wikipedia.org/wiki/IEEE_802.3 for a look at the Ethernet standard’s history and future versions. This page also lists the IEEE document names for each standard. • • 802.11 Wi-Fi • • 1. Discuss the various options for wireless transmission speed and protocol standards available. • a. Discuss the frequencies used by the most common of the wireless standards: a, b, g, and n. • • Wi-Fi Modes • • 1. Students should be made aware of the differences between infrastructure mode and ad hoc mode. • a. Infrastructure implies a central device connecting all the devices, while ad hoc is a quick and dirty peer-to-peer method of connecting; for example, laptops to cell phones, or laptops to other laptops. • • Wi-Fi Communication Channels • • 1. Illustrate how wireless splits an allocated spectrum into various channels and how communication occurs on these channels. • a. Students should know how many channels are available for a given wireless standard, such as 14 for 802.11g (11 in the U.S.) or 42 for 802.11a. • b. Discuss the effects of interference when two access points use the same channel in proximity to each other. • c. Discuss the nonoverlapping channels for various wireless standards (1, 6, 11 for 802.11g). • d. Describe some of the available encryption/access control methods for wireless networks. • e. Compare CSMA/CD to 802.11’s CSMA/CA and how it affects multiple PCs connected to a single access point in infrastructure mode. • f. Discuss the range of wireless technologies and how overhead affects that range or transmission speed available. • • Teaching Tip • Have students review Simulation 8—Basic Wi-Fi Operation on the book’s CD. • Token Ring Networks • • 1. Discuss the 802.5 token ring standard. • a. What media is required for token ring? • b. Maximum transmission speeds for token ring? • 2. Explain how token ring uses a token-passing method to control transmissions. • a. This avoids the need for CSMA/CD, but also becomes a limiting factor for speeds. • Fiber Distributed Data Interface Technology • • 1. Describe the dual-ring FDDI technology. • a. Despite the limitations of using ring technology, FDDI accomplished 100 Mbps speeds. • b. The main disadvantage for this technology when it was in use was cost, but it had a definite speed advantage. • Internet Access Technologies • • 1. Discuss the technologies used by SOHOs to connect to the Internet, their speeds, and their disadvantages. • a. Describe how cable Internet technology works, using a variety of standards and media. Cable modems are connected to CATV coaxial cable, the same media used to deliver cable television. Cable technology uses shared media network access, however. • b. Describe how Digital Subscriber Line (DSL) connections work over existing phone lines, making it widely available. Students should be aware of the distance from the Central Office (CO) limitation. Mention the differences between asymmetric DSL versus symmetric DSL. • c. Describe how satellite connections work. Emphasize the chief advantage—availability. So long as you can point a dish at a satellite, you have connectivity regardless of area. Also emphasize the main disadvantages—speed and cost. • d. Describe the WiMAX standards and how they provide mobility for users in more urban environments where this technology is most widely deployed. Make sure to mention the speeds available, which are impressive for such a mobile technology. • • Quick Quiz 3 • 1. What is the networking standard for wireless networking (also known as Wireless Fidelity or Wi-Fi). • Answer: 802.11 • • 2. Token ring originally operated at _________. • Answer: 4 Mbps • • 3. Which media access method is used by FDDI? • Answer: token passing • 4. _________ is a broadband technology used to deliver Internet access to homes and businesses over standard cable television (CATV) coaxial cable. • Answer: cable modem networking • Class Discussion Topics • 1. Have students discuss what technologies they might see in use at an enterprise. For example, where would you most likely see fiber-optic Ethernet technologies? Or where might wireless technologies be deployed? • Additional Projects • 1. Get students to take a look at some of the older legacy Ethernet technologies, and discuss how things have changed in the time since these technologies. Compare how old technologies made use of old media in contrast to new technologies. How would 10 Gbps work on copper media? What about 100 Gbps? Is this possible? • Additional Resources • • 1. http://en.wikipedia.org/wiki/Fiber_optic for a look at fiber-optic media • 2. http://en.wikipedia.org/wiki/Wireless_networks#Types_of_wireless_connections • Key Terms • 1000BaseT Ethernet Defined by the IEEE 802.3ab standard, supports 1000 Mbps Ethernet (usually called Gigabit Ethernet) over Category 5 or higher UTP cable using baseband signaling. 100BaseFX 100 Mbps Ethernet using baseband signaling over two strands of fiber-optic cabling. 100BaseTX Defined by IEEE 802.3u, it is the most commonly used Ethernet variety today. It runs over Category 5 or higher UTP cable and uses two of the four wire pairs: one to transmit data and the other to receive data. It runs at 100 Mbps using baseband signaling. 10BaseT Defined by IEEE 802.3i, it is Ethernet running at 10 Mbps using baseband signaling over Category 3 or higher twisted-pair cabling. While still seen in older networks, newer networks use 100BaseT or faster technology. 10GBaseT Defined by IEEE 802.3an it is 10 Gigabit Ethernet running over four pairs of Category 6A UTP cabling using baseband signaling. Unlike the other BaseT Ethernet standards, 10GBaseT operates only in full-duplex mode. ad hoc mode Sometimes called peer-to-peer mode, it is a wireless mode of operation typically used only in small or temporary installations. There’s no central device, and data travels from one device to another to reach the destination device. asymmetric DSL (ADSL) A DSL variant in which the download and upload speeds differ substantially, so the data rates aren’t symmetrical. Typical connection speeds for downloading data range from 256 Kbps to 8 Mbps; upload speeds are typically much slower, in the range of 16 Kbps to 640 Kbps. See also Digital Subscriber Line (DSL). baseband A type of signaling used in networks in which each bit of data is represented by a pulse of electricity (on copper media) or light (on fiber-optic media). These signals are sent at a single fixed frequency, using the medium’s entire bandwidth. LAN technologies used baseband signaling. broadband A type of signaling that uses analog techniques to encode binary 1s and 0s across a continuous range of values. Broadband signals move across the medium in the form of continuous electromagnetic or optical waves rather than discrete pulses. Signals flow at a particular frequency, and each frequency represents a channel of data, allowing multiple streams of data on a single wire. TV and cable Internet use broadband signaling. carrier sense multiple access with collision avoidance (CSMA/CA) An access control method used by Wi-Fi networks in which an acknowledgment is required for every packet sent, thereby avoiding most possibilities of a collision (collision avoidance). See also CSMA/CD. Carrier Sense Multiple Access with Collision Detection (CSMA/CD) A media access method in which a device must first listen (carrier sense) to the media to be sure no other device is transmitting. If two devices transmit at the same exact time (multiple access), a collision occurs and is detected (collision detection). In this case all devices involved in the collision wait for a random period of time before transmitting again. collision domain The extent to which signals in an Ethernet bus topology network are propagated. All devices connected to a logical bus topology network are in the same collision domain. Switch and router ports delimit collision domains. collision The result of two or more devices on the same medium transmitting simultaneously when CSMA/CD is the media access method in use. See also Carrier Sense Multiple Access with Collision Detection (CSMA/CD). Cyclic Redundancy Check (CRC) The error-checking code in an Ethernet frame’s trailer, which is the result of a mathematical algorithm computed on the frame data. When the frame is received by the destination device, the calculation is repeated. If the results of this calculation don’t match the CRC in the frame, it indicates the data was altered in some way. Data Over Cable Service Interface Specification (DOCSIS) The official standard governing cable modem operation. Digital Subscriber Line (DSL) A broadband technology that uses existing phone lines to carry voice and data simultaneously. extended star topology An extension of the physical star topology in which a central switch or hub is the central connecting point for other switches or hubs that have computers and other network devices attached to them, forming a star or stars. See also physical star topology. Fiber Distributed Data Interface (FDDI) Uses the token-passing media access method and dual rings for redundancy. The rings in an FDDI network are usually a physical ring of fiber-optic cable. FDDI transmits at 100 Mbps and can include up to 500 nodes over a distance of 100 kilometers. frame types The format of a frame that describes the content and length of the frame header. Gigabit Ethernet See 1000BaseT Ethernet. infrastructure mode An operational mode for Wi-Fi networks in which wireless stations connect through a wireless access point before they can begin communicating with other devices. logical topology The path data travels between computers on a network. The most common logical topologies are switched, bus, and ring. media access control A set of rules governing how and when the medium can be accessed for transmission. The rules ensure that data is transmitted and received in an orderly fashion and all stations have an opportunity to communicate. Also called media access method. media access method See media access control. mesh topology A topology in which each device in the network is connected to every other device, providing multiple pathways in the event of a device or cable failure. network backbone The cabling used to communicate between LANs or between hubs or switches. The backbone cabling often runs at a faster speed than the cabling used to connect computers because the backbone must carry data from many computers to other parts of the network. physical bus topology A network topology in which a continuous length of cable connects one computer to another in daisy-chain fashion. There is no central interconnecting device. physical ring topology A cabling arrangement in which each device is connected to another device in daisy-chain fashion, and the last device connects back to the first device forming a ring. Used by token ring and FDDI, the physical ring is rarely used anymore. physical star topology A network topology that uses a central device, such as a hub or switch, to interconnect computers in a LAN. Each computer has a single length of cable going from its NIC to the central device. This is the most common physical topology used in LANs. physical topology The arrangement of cabling, and how the cables connect one device to another in a network. The most common physical topology is a star but there is also a bus, ring, point-to-point, and mesh. point-to-point topology Cabling that creates a direct link between two devices. This topology is most often used in WANs or in wireless networks to create a wireless bridge. reflection See signal bounce. signal bounce The term used when electricity bounces off the end of a cable and back in the other direction. Signal bounce causes corruption of data as the bouncing signal collides with signals behind it. A terminator at each cable end is needed to prevent signal bounce. Also called reflection. signal propagation The travel of signals across the medium and through any connectors and connecting devices until the signal weakens sufficiently to be undetectable or is absorbed by a termination device.. symmetric DSL (SDSL) A DSL variant in which the download and upload speeds are equivalent, or symmetrical. See also Digital Subscriber Line (DSL). terminator An electrical component called a resistor that is placed at the ends of a physical bus network to absorb the signal instead of allowing it to bounce back up the wire. token ring Based on the IEEE 802.5 standard, token ring networks are cabled in a physical star topology but function as a logical ring. It uses the token-passing media access method whereby a special frame called the “token” passes from one computer to the next. Only the computer holding the token can send data. wireless bridge. An operational mode of wireless networking usually used to connect two wired LANs together that are separated from each other in such a way that using physical media is impractical. A wireless bridge can also be used to extend the reach of a wireless network. Wireless Fidelity (Wi-Fi) The common name given to the 802.11 series of IEEE standards that define four common varieties of wireless LAN, including 802.11a, 802.11b, 802.11g, and 802.11n. Worldwide Interoperability for Microwave Access (WiMax) Wireless broadband technology defined in 802.16-2004 for fixed WiMax and 802.16e for mobile WiMax. WiMax is considered a fourth-generation (4G) technology for bringing wireless Internet access to remote areas, large areas up to a mile radius, and mobile users. Technical Notes for Hands-On Projects • • Hands-On Project 3-1: Requires 3 computers and a hub, along with patch cables to connect all devices. Each station needs the Wireshark protocol analyzer installed. • Hands-On Project 3-2: One computer is enough for this project. The operating system is assumed to be Windows 7 and may require different procedures to complete the lab depending on what OS is actually used. • Hands-On Project 3-3: Requires one computer with Wireshark installed. Operating system is once again assumed to be Windows 7. Wireshark sometimes will fail to display any available network adapters on Windows 7 when trying to select a capture device. If this occurs, you will need to be able to right-click the Wireshark shortcut or program and select “Run as administrator”. • Hands-On Project 3-4: 2+ computers with wireless NICs are required. OS is assumed to be Windows 7, but similar steps to set up an ad hoc network are available on Windows XP and Vista. • Challenge Lab 3-1: Several switches/hubs will be needed to complete this lab; preferably use a variety of each. • Challenge Lab 3-2: Use network assembled from 3-1, with the additional requirements of an access point and PCs with wireless NICs available. • Challenge Lab 3-3: Lab requires a copy of inSSIDer software to be installed (link: http://metageek.net). • • Using Virtualization for Hands-On Projects • • The following Hands-On Projects/Challenge Labs have been identified as those that students can do using virtual machines rather than physical machines. • Hands-On Project 3-3 Instructor Manual for Guide to Networking Essentials Gregory Tomsho 9781111312527, 9781305105430, 9788131502136
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