CH-4-6 Introduction to TCP/IP Protocols – Network+ Guide to Networks : Chapter Notes

This Document Contains Chapters 4 to 6 Chapter 4 Introduction to TCP/IP Protocols At a Glance Instructor’s Manual Table of Contents • Overview • Objectives • Teaching Tips • Quick Quizzes • Class Discussion Topics • Additional Projects • Additional Resources • Key Terms Lecture Notes Overview A protocol is a rule that governs how networks communicate. Protocols define the standards for communication between network devices. Without protocols, devices could not interpret the signals sent by other devices, and data would go nowhere. In this chapter, the student will learn about the most commonly used networking protocols, their components, and their functions. This chapter is not an exhaustive study of protocols, but rather a practical guide to applying them. In the sections that follow, the student will learn about the networking protocol suite that is used on virtually all LANs and WANs today - TCP/IP. Other protocol suites, such as IPX/SPX, NetBIOS, and AppleTalk, do exist. However, these protocols have been replaced by TCP/IP on modern networks. Chapter Objectives After reading this chapter and completing the exercises, the student will be able to: • Identify and explain the functions of the core TCP/IP protocols • Explain the TCP/IP model and how it corresponds to the OSI model • Discuss addressing schemes for TCP/IP in IPv4 and IPv6 and explain how addresses are assigned automatically using DHCP (Dynamic Host Configuration Protocol) • Describe the purpose and implementation of DNS (Domain Name System) • Identify the well-known ports for key TCP/IP services • Describe common Application layer TCP/IP protocols are used Teaching Tips Characteristics of TCP/IP (Transmission Control Protocol/ Internet Protocol) 1. Introduce the TCP/IP protocol. 2. Emphasize that it is a suite of specialized protocols and provide examples. 3. Note the additional terms that are used to reference the TCP/IP protocol suite. 4. Briefly discuss the history of TCP/IP. 5. Explain why TCP/IP has become so popular. 6. Define the term routable and explain its importance in large networks. 7. Discuss why flexibility is important in the TCP/IP suite. The TCP/IP Model 1. Introduce the concept of TCP/IP model. 2. Discuss that the model roughly lines up with the OSI model consolidating the seven layers into only four layers. 3. Explain that the layers are Application (OSI Application/Presentation/Session), Transport, Internet (OSI Network), and Network Access (OSI Data Link and Physical). 4. Remind students that the TCP/IP model developed after the protocols were in widespread use. The TCP/IP Core Protocols 1. Introduce the concept of TCP/IP core protocols. 2. Describe where the core protocols operate in the OSI model. 3. Mention the two most significant core protocols. TCP (Transmission Control Protocol) 1. Introduce TCP (Transmission Control Protocol) and describe its purpose. 2. Mention the layer of the OSI model in which it operates. 3. Explain characteristics of the Transport layer that affect TCP transmissions. 4. Use Figure 4-2 to illustrate the format of a TCP segment. 5. Explain how the segment becomes the IP datagram’s “data.” 6. Describe the fields belonging to the TCP segment. 7. Use Figure 4-3 to walk through an example interpreting a TCP segment. 8. Use Figure 4-4 to illustrate how a TCP connection is established. 9. Emphasize the contents of the three segments transmitted. UDP (User Datagram Protocol) 1. Introduce UDP (User Datagram Protocol) and describe its purpose. 2. Mention the layer of the OSI model in which it operates. 3. Explain characteristics of the Transport layer that affect UDP transmissions. 4. Describe a situation that makes UDP valuable. 5. Use Figure 4-5 to illustrate the format of a UDP segment. 6. Describe the fields belonging to the UDP segment. 7. Contrast the UDP segment in Figure 4-5 with the much larger TCP segment in Figure 4-2. IP (Internet Protocol) 1. Introduce IP (Internet Protocol) and describe its purpose. 2. Mention the layer of the OSI model in which it operates. 3. Remind students that at the Network layer of the OSI model, data is formed into packets. 4. Explain that in the IP protocol, the packet is called an IP datagram. 5. Explain the purpose of the IP datagram. 6. Explain characteristics of the IP protocol. 7. Use Figure 4-6 to illustrate the format of an IP datagram. 8. Describe the fields belong to the IP datagram. 9. Use Figure 4-7 to walk through an example interpreting an IP datagram. 10. Use Figure 4-8 to illustrate the format of an IPv6 packet header, and figure 4-9 to illustrate an example of an IPv6 packet. 11. Ensure students understand the length and other structural differences between IPv4 and IPv6 packets. Teaching Tip Students may find the original RFC standards at http://www.rfc-editor.org/categories/rfc-standard.html IGMP (Internet Group Management Protocol) 1. Introduce the IGMP (Internet Group Management Protocol or Internet Group Multicast Protocol) and describe its purpose. 2. Mention the layer of the OSI model in which IGMP operates. 3. Define and explain the term multicasting. ARP (Address Resolution Protocol) 1. Introduce ARP (Address Resolution Protocol) and describe its purpose. 2. Define an ARP table and describe how it helps ARP operate efficiently. 3. Use Figure 4-10 to illustrate what an ARP table might look like. 4. Introduce the two types of entries an ARP table can contain. 5. Define and describe dynamic ARP table entries. 6. Define and describe static ARP table entries. 7. Describe how the ARP utility is accessed and what it provides. ICMP (Internet Control Message Protocol) 1. Introduce ICMP (Internet Control Message Protocol) and describe its purpose. 2. Mention the layer of the OSI model in which ICMP operates. 3. Describe the types of errors ICMP may report. 4. Emphasize that ICMP cannot correct the errors it reports. Teaching Tip Students may find more information on Address Resolution Protocol (ARP) at http://technet.microsoft.com/en-us/library/cc758357.aspx IPv4 Addressing 1. Review the two types of addresses networks recognize. 2. Define an IP address. 3. Explain the makeup of an IP address. 4. Mention the two types of information an IP address may contain. 5. Explain how to determine the network class. 6. Describe the three types of network classes used for LANs in traditional IP addressing. 7. Use Table 4-4 to illustrate characteristics of the three commonly used classes of TCP/IP-based networks. 8. Mention the existence of Class D and Class E addresses and note that they are rarely used. 9. Explain the possible combinations used to identify networks and hosts in an IP address. 10. Explain the use of the number zero as a placeholder. 11. Explain the use of the number 255 in broadcast transmissions. 12. Describe how a portion of each IP address contains clues about the network class. 13. Use Figure 4-8 to illustrate IP addresses and their classes. 14. Explain the need for a new addressing scheme to meet IP address demands. 15. Define and explain the loopback address. 16. Define and explain a loopback test. 17. Explain the Windows command used to view IP information. 18. Explain the UNIX and Linux command used to view IP information. 19. Use Figure 4-12 to illustrate results of the ipconfig /all command on a Windows workstation. 20. Use Figure 4-13 to illustrate results of the ifconfig -a command on a UNIX or Linux workstation. Binary and Dotted Decimal Notation 1. Define and explain dotted decimal notation. 2. Mention that each number in a dotted decimal address has a binary equivalent. 3. Explain how to convert a dotted decimal address to its binary equivalent. Subnet Mask 1. Define and describe a subnet mask. 2. Explain the components of a subnet mask. 3. Explain how subnet masks are assigned. 4. Define the term net mask. 5. Define and explain subnetting. 6. Use Table 4-5 to illustrate default subnet mask values. Teaching Tip Students may find more information on understanding TCP/IP addressing and subnetting basics at http://support.microsoft.com/kb/164015 IPv6 Addressing 1. Review the increased length of IPv6 addresses. 2. Explain the hexadecimal notation used for IPv6 addresses. 3. Remind students of the proper way to use IPv6 shorthand notation for addresses. 4. Explain to students that an IPv6 address can demonstrate the address’ scope, whether that is a single node, group or a special group. 5. Explain the Format Prefix of IPv6 addresses. Teaching Tip Students may find more information on IPv6 concepts at http://technet.microsoft.com/en-us/library/cc785929.aspx Assigning IP Addresses 1. Review how IP addresses are monitored and handed out. 2. Mention that every node on a network must have a unique IP address. 3. Explain what happens if duplicate IP addresses exist on a network. 4. Explain how to assign IP address manually. 5. Define the term static address. DHCP (Dynamic Host Configuration Protocol) 1. Define and explain DHCP (Dynamic Host Configuration Protocol). 2. Mention the layer of the OSI model in which DHCP operates. 3. Explain how DHCP operates noting the differences from BOOTP. 4. Describe the reasons for implementing DHCP. DHCP Leasing Process 1. Define and explain DHCP leasing. 2. Explain how a client obtains its DHCP-assigned address. 3. Explain how the length of time a lease remains in effect is determined. 4. Explain how to configure the DHCP service. 5. Describe the steps negotiate the client’s first lease. 6. Use Figure 4-11 to illustrate the DHCP leasing process. Terminating a DHCP Lease 1. Explain how a DHCP lease expires. 2. Explain how to release TCP/IP settings on a computer running the Windows XP operating system. 3. Explain how to obtain a new IP address on a Windows XP workstation. Private and Link-Local Addresses 1. Remind students that a client cannot communicate without a valid IP address. 2. Explain the link-local address and Zeroconf (Zero Configuration) protocol. 3. Explain how Microsoft handles the problem of no DHCP server to assign a valid DHCP address. 4. Explain how APIPA (Automatic Private IP Addressing) operates. 5. Describe the drawbacks of the IP address assigned by APIPA. 6. Discuss how to check whether a computer running a Windows operating system is using APIPA. 7. Explain why it is acceptable to leave APIPA enabled. Teaching Tip Students may find out more on how to use automatic TCP/IP addressing without a DHCP server at http://support.microsoft.com/kb/220874 Quick Quiz 1 1. TCP/IP is a ____ of protocols. a. series b. set c. selection d. suite Answer: D 2. TCP (Transmission Control Protocol) operates in the ___ layer of the OSI model. Answer: Transport 3. ____ is a Network layer protocol that reports on the success or failure of data delivery. Answer: ICMP (Internet Control Message Protocol) 4. With DHCP, a device borrows, or ____ an IP address while it is attached to the network. Answer: leases 5. True or False: It is unacceptable to leave APIPA enabled if it is not needed. Answer: False Sockets and Ports 1. Introduce a process and the need for a unique process address. 2. Define and explain a port number. 3. Define and explain a process’s socket. 4. Describe the advantage of using port numbers. 5. Use Figure 4-15 to illustrate a virtual connection for the Telnet service. 6. Define the range for port numbers. 7. Explain the three types of port numbers: a. Well known b. Registered ports c. Dynamic and/or Private Ports 8. Use Table 4-6 to illustrate commonly used TCP/IP port numbers. 9. Explain the editable, text-based file servers maintained for ports. Teaching Tip Students may find more information on network ports used by key Microsoft Server products at: http://www.microsoft.com/smallbusiness/support/articles/ref_net_ports_ms_prod.mspx Host Names and DNS (Domain Name System) 1. Note that TCP/IP addressing involves numbers. 2. Explain how this is great for computers; however, most people can remember words better than numbers. 3. Define and explain a host. 4. Define and explain a host name. Domain Names 1. Define and explain a domain. 2. Define and explain a domain name. 3. Explain what is meant by a fully qualified host name. 4. Define and explain labels noting that each label represents a level in the domain naming hierarchy. 5. Explain how domain names are registered. 6. Use Table 4-7 to illustrate ICANN-approved top-level domains. 7. Note that ICANN has approved 240 country code top-level domains. 8. Explain the advantage of reserving a domain name. 9. Describe host and domain names restrictions. Host Files 1. Describe how ARPAnet used HOSTS.TXT. 2. Explain why ARPAnet’s arrangement became outdated. 3. Explain why it is important to know about host files. 4. Use Figure 4-16 to illustrate an example of such a host file. 5. Explain where host files are stored in Windows and UNIX/Linux. DNS (Domain Name System) 1. Introduce and describe DNS (Domain Name System or Domain Name Service). 2. Explain the meanings of DNS. 3. Describe why the DNS service is divided into three components. 4. Define and describe resolvers. 5. Define and describe name servers. 6. Define and describe a namespace. 7. Use Figure 4-17 as an example to illustrate domain name resolution. 8. Explain how resource records come in many different types, depending on their function. 9. Describe the fields in a resource record. 10. Explain how DNS was updated in the past and how it is updated today. Configuring DNS 1. Explain how to manually configure the values in a workstation’s TCP/IP properties. 2. Use Figure 4-18 to illustrate a Windows 7 Internet Protocol (TCP/IP) Properties dialog box. DDNS (Dynamic DNS) 1. Define and describe DDNS (Dynamic DNS). 2. Note that DDNS does not take the place of DNS. Teaching Tip Students may find more information on DNS at http://technet.microsoft.com/en-us/network/bb629410.aspx Application Layer Protocols 1. Explain how Application layer protocols work over TCP or UDP plus IP. 2. Remind students of Application layer protocols discussed earlier. 3. Introduce the new Application layer protocols. Telnet 1. Define and explain Telnet. 2. Explain the security concern with using Telnet. 3. Mention a more secure alternative. FTP (File Transfer Protocol) 1. Define and explain FTP (File Transfer Protocol). 2. Describe how FTP commands work. 3. Define and describe anonymous logons. 4. Review some useful FTP commands and their syntax. 5. Define and explain graphical FTP clients. 6. Describe how a student may use FTP in the Web browser. 7. Describe how a student may use FTP from a modem. 8. Explain the security concern with using FTP. 9. Mention a more secure alternative. TFTP (Trivial File Transfer Protocol) 1. Define and explain TFTP (Trivial File Transfer Protocol). 2. Explain the advantages and drawbacks with TFTP. 3. Explain the security concern with TFTP. NTP (Network Time Protocol) 1. Define and explain NTP (Network Time Protocol) 1. Explain the critical nature of NTP. 2. Explain why NTP benefits from UDPs quick, connectionless nature at the Transport layer. PING (Packet Internet Groper) 1. Define and explain Ping (Packet Internet Groper). 2. Explain how Ping uses ICMP services. 3. Note that an IP address or a host name may be pinged. 4. Use Figure 4-19 to illustrate examples of a successful and an unsuccessful Ping test. 5. Describe what happens when the loopback address is pinged. Note the significance of this action in terms of troubleshooting. 6. Describe the different Ping command options, switches, and the syntax of the command. 7. Explain how to get help with the Ping command. Teaching Tip Students may find more information on OSI layers at http://computer.howstuffworks.com/osi1.htm Quick Quiz 2 1. IPv6 addresses are composed of ____ bits. a. 32 b. 64 c. 128 d. 256 Answer: C 2. Which IPv6 address type represents a single interface on a device? a. Unicast b. Multicast c. Anycast d. Singlecast Answer: A 3. Every process on a machine is assigned a(n) ____ number. Answer: port 4. A domain name is represented by a series of character strings, called labels, separated by ____. Answer: dots 5. True or False: Host files are the best automated solution for assigning IP addresses. Answer: False 6. True or False: Telnet is generally considered to be insecure. Answer: True Class Discussion Topics 1. As a class, compare and contrast Telnet and FTP. 2. Discuss whether there are additional components that could be added to the IPv4 protocol to enhance its usefulness. Additional Projects 1. Have each student research five graphical FTP interfaces and write a report summarizing their findings. The report should include a comparison of features, price, security, and popularity. 2. The future of the Internet will lie with IPv6. Have the students research the components of the protocol and compare the various TCP/IPv6 layers with the OSI model. The report should also include a section discussing additional functions or components that would be beneficial in IPv6. Additional Resources 1. IBM TCP/IP RedBook http://www.redbooks.ibm.com/abstracts/gg243376.html 2. TCP/IP Fundamentals for Microsoft Windows: Overview http://technet.microsoft.com/en-us/library/bb726983.aspx 3. IPv6 http://www.ipv6.org 4. Microsoft IPv6 http://technet.microsoft.com/en-us/network/bb530961.aspx 5. Internet Protocol Version 6 Basics http://h20195.www2.hp.com/v2/GetPDF.aspx/4AA3-5764ENW.pdf Key Terms  Address Resolution Protocol See ARP.  address resource record A type of DNS data record that maps the IP address of an Internet-connected device to its domain name.  alias A nickname for a node’s host name. Aliases can be specified in a local host file.  anycast address A type of address specified in IPv6 that represents a group of interfaces, any one of which (and usually the first available of which) can accept a transmission. At this time, anycast addresses are not designed to be assigned to hosts, such as servers or workstations, but rather to routers.  APIPA (Automatic Private IP Addressing) A service available on computers running one of the Windows operating systems that automatically assigns the computer’s network interface a link-local IP address.  ARP (Address Resolution Protocol) A core protocol in the TCP/IP suite that belongs in the Network layer of the OSI model. ARP obtains the MAC (physical) address of a host, or node, and then creates a local database that maps the MAC address to the host’s IP (logical) address.  ARP cache See ARP table.  ARP table A database of records that maps MAC addresses to IP addresses. The ARP table is stored on a computer’s hard disk where it is used by the ARP utility to supply the MAC addresses of network nodes, given their IP addresses.  Automatic Private IP Addressing See APIPA.  Avahi A version of Zeroconf available for use with the Linux operating system.  Bonjour Apple’s implementation of the Zeroconf group of protocols.  country code TLD A top-level domain that corresponds to a country. For example, the country code TLD for Canada is .ca, and the country code TLD for Japan is .jp.  datagram See data packet.  DDNS (Dynamic DNS) A method of dynamically updating DNS records for a host. DDNS client computers are configured to notify a service provider when their IP addresses change, then the service provider propagates the DNS record change across the Internet automatically.  DHCP (Dynamic Host Configuration Protocol) An Application layer protocol in the TCP/IP suite that manages the dynamic distribution of IP addresses on a network. Using DHCP to assign IP addresses can nearly eliminate duplicate-addressing problems.  DHCP scope The predefined range of addresses that can be leased to any network device on a particular segment.  DHCP server A server that manages IP address assignment, maintaining information about which addresses are allowable, which are available, and which have already been associated with a host.  DHCPv4 The version of DHCP used with IPv4. DHCPv4 uses port number 67 for client-to-server communications and port number 68 for server-to-client communications.  DHCPv6 The version of DHCP used with IPv6. DHCPv6 uses port number 546 for client-to-server communications and port number 547 for server-to-client communications.  diskless workstation A workstation that doesn’t contain a hard disk, but instead relies on a small amount of read-only memory to connect to a network and to pick up its system files.  DNS (Domain Name System or Domain Name Service) A hierarchical way of tracking domain names and their addresses, devised in the mid-1980s. The DNS database does not rely on one file or even one server, but rather is distributed over several key computers across the Internet to prevent catastrophic failure if one or a few computers go down. DNS is a TCP/IP service that belongs to the Application layer of the OSI model.  DNS cache A database on a computer that stores information about IP addresses and their associated host names. DNS caches can exist on clients as well as on name servers.  DNS server See name server.  DNS zone A portion of the DNS namespace for which one organization is assigned authority to manage.  domain A group of computers that belong to the same organization and have part of their IP addresses in common.  domain name The symbolic name that identifies a domain. Usually, a domain name is associated with a company or other type of organization, such as a university or military unit.  Domain Name Service See DNS.  Domain Name System See DNS.  dotted decimal notation The shorthand convention used to represent IPv4 addresses and make them more easily readable by humans. In dotted decimal notation, a decimal number between 0 and 255 represents each binary octet. A period, or dot, separates each decimal.  dual-stack A type of network that supports both IPv4 and IPv6 traffic.  dynamic ARP table entry A record in an ARP table that is created when a client makes an ARP request that cannot be satisfied by data already in the ARP table.  Dynamic DNS See DDNS.  Dynamic Host Configuration Protocol See DHCP.  Dynamic Host Configuration Protocol version 4 See DHCPv4.  Dynamic Host Configuration Protocol version 6 See DHCPv6.  dynamic IP address An IP address that is assigned to a device upon request and may change when the DHCP lease expires or is terminated. BOOTP and DHCP are two ways of assigning dynamic IP addresses.  Dynamic Ports TCP/IP ports in the range of 49,152 through 65,535, which are open for use without requiring administrative privileges on a host or approval from IANA.  echo reply The response signal sent by a device after another device pings it.  echo request The request for a response generated when one device pings another device.  File Transfer Protocol See FTP.  flow A sequence of packets issued from one source to one or many destinations. Routers interpret flow information to ensure that packets belonging to the same transmission arrive together. Flow information may also help with traffic prioritization.  Format Prefix A variable-length field at the beginning of an IPv6 address that indicates what type of address it is (for example, unicast, anycast, or multicast).  FQDN (fully qualified domain name) A host name plus domain name that uniquely identifies a computer or location on a network.  FTP (File Transfer Protocol) An Application layer protocol used to send and receive files via TCP/IP.  fully qualified domain name See FQDN.  fully qualified host name See FQDN.  hop A term used to describe each trip a unit of data takes from one connectivity device to another. Typically, hop is used in the context of router-to-router communications.  hop limit See TTL.  host file A text file that associates TCP/IP host names with IP addresses.  host name A symbolic name that describes a TCP/IP device.  hosts The name of the host file used on UNIX, Linux, and Windows systems. On a UNIX- or Linux-based computer, hosts is found in the /etc directory. On a Windows-based computer, it is found in the %systemroot%system32driversetc folder.  ICMP (Internet Control Message Protocol) A core protocol in the TCP/IP suite that notifies the sender that something has gone wrong in the transmission process and that packets were not delivered.  ICMPv6 The version of ICMP used with IPv6 networks. ICMPv6 performs the functions that ICMP, IGMP, and ARP perform in IPv4. It detects and reports data transmission errors, discovers other nodes on a network, and manages multicasting.  ifconfig A TCP/IP configuration and management utility used with UNIX and Linux systems.  IGMP (Internet Group Management Protocol or Internet Group Multicast Protocol) A TCP/IP protocol used on IPv4 networks to manage multicast transmissions. Routers use IGMP to determine which nodes belong to a multicast group, and nodes use IGMP to join or leave a multicast group.  Internet Control Message Protocol See ICMP.  Internet Control Message Protocol version 6 See ICMPv6  Internet Group Management Protocol See IGMP.  Internet Group Multicast Protocol See IGMP.  internetwork To traverse more than one LAN segment and more than one type of network through a router.  IP datagram See IP packet.  IP next generation See IPv6.  IP packet The IP portion of a TCP/IP frame that acts as an envelope for data, holding information necessary for routers to transfer data between subnets.  IP version 4 Link Local See IPv4LL.  ipconfig The utility used to display TCP/IP addressing and domain name information in the Windows client operating systems.  IPng See IPv6.  IPv4 IP version 4, the Internet Protocol standard released in the 1980s and still commonly used on modern networks. It specifies 32-bit addresses composed of four octets. It lacks the security, automatic addressing, and prioritization benefits of IPv6. It also suffers from a limited number of addresses, a problem that can be resolved by using IPv6 instead.  IPv4LL (IP version 4 Link Local) A protocol that manages automatic address assignment among locally connected nodes. IPv4LL is part of the Zeroconf group of protocols.  IPv6 (IP version 6) A newer standard for IP addressing that is gradually replacing the current IPv4 (IP version 4). Most notably, IPv6 uses a newer, more efficient header in its packets and allows for 128-bit source and destination IP addresses. The use of longer addresses will allow for many more IP addresses to be in circulation. IPv6 also provides automatic addressing, better security, and prioritization features.  label A character string that represents a domain (either top-level, second-level, or third-level).  lease The agreement between a DHCP server and client on how long the client can use a DHCP-assigned IP address. DHCP services can be configured to provide lease terms equal to any amount of time.  link-local address An IP address that is automatically assigned by an operating system to allow a node to communicate over its local subnet if a routable IP address is not available. ICANN has established the range of 169.254.0.0 through 169.254.254.255 as potential link-local IPv4 addresses. IPv6 link-local addresses begin with FE80.  loopback address An IP address reserved for communicating from a node to itself (used mostly for troubleshooting purposes). The IPv4 loopback address is always cited as 127.0.0.1, although in fact, transmitting to any IP address whose first octet is 127 will contact the originating device. In IPv6, the loopback address is represented as ::1.  loopback test An attempt to contact one’s own machine for troubleshooting purposes. In TCP/IP-based networking, a loopback test can be performed by communicating with an IPv4 address that begins with an octet of 127. Usually, this means pinging the address 127.0.0.1.  mask See subnet mask.  multicast address A type of address in the IPv6 that represents multiple interfaces, often on multiple nodes. An IPv6 multicast address begins with the following hexadecimal field: FF0x, where x is a character that identifies the address’s group scope.  multicasting A means of transmission in which one device sends data to a specific group of devices (not necessarily the entire network segment) in a point-to-multipoint fashion.  name server A server that contains a database of TCP/IP host names and their associated IP addresses. A name server supplies a resolver with the requested information. If it cannot resolve the IP address, the query passes to a higher-level name server.  namespace The database of Internet IP addresses and their associated names distributed over DNS name servers worldwide.  net mask See subnet mask.  network class A classification for TCP/IP-based networks that pertains to the network’s potential size and is indicated by an IP address’s network ID and subnet mask. Network Classes A, B, and C are commonly used by clients on LANs; network Classes D and E are reserved for special purposes.  network ID The portion of an IP address common to all nodes on the same network or subnet.  Network Time Protocol See NTP.  NTP (Network Time Protocol) A simple Application layer protocol in the TCP/IP suite used to synchronize the clocks of computers on a network. NTP depends on UDP for Transport layer services.  octet One of the 4 bytes that are separated by periods and together make up an IPv4 address.  Packet Internet Groper See PING.  ping To send an echo request signal from one node on a TCP/IP-based network to another, using the PING utility. See also PING.  PING (Packet Internet Groper) A TCP/IP troubleshooting utility that can verify that TCP/IP is installed, bound to the NIC, configured correctly, and communicating with the network. PING uses ICMP to send echo request and echo reply messages that determine the validity of an IP address.  ping6 The version of the PING utility used on Linux computers that run IPv6.  port number The address on a host where an application makes itself available to incoming data.  private address An IP address used only on an organization’s internal network. Certain IP address ranges are reserved for private addresses. Private addresses cannot be used to communicate over the Internet.  Private Port See Dynamic Ports.  public address An IP address that is valid for use on public networks, such as the Internet. An organization assigns its hosts public addresses from the range of addresses assigned to it by Internet numbering authorities.  Registered Ports The TCP/IP ports in the range of 1024 to 49,151. These ports are accessible to network users and processes that do not have special administrative privileges. Default assignments of these ports must be registered with IANA.  resolver Any host on the Internet that needs to look up domain name information.  resource record The element of a DNS database stored on a name server that contains information about TCP/IP host names and their addresses.  root server A DNS server maintained by ICANN and IANA that is an authority on how to contact the top-level domains, such as those ending with .com, .edu, .net, .us, and so on. ICANN oversees the operation of 13 root servers around the world.  routable The protocols that can span more than one LAN because they carry Network layer and addressing information that can be interpreted by a router.  socket A logical address assigned to a specific process running on a computer. Some sockets are reserved for operating system functions.  static ARP table entry A record in an ARP table that someone has manually entered using the ARP utility. Static ARP table entries remain the same until someone manually modifies them with the ARP utility.  static IP address An IP address that is manually assigned to a device and remains constant until it is manually changed.  subnet A part of a network in which all nodes shares a network addressing component and a fixed amount of bandwidth.  subnet mask In IPv4 addressing, a 32-bit number that, when combined with a device’s IP address, indicates what kind of subnet the device belongs to.  subnetting The process of subdividing a single class of network into multiple, smaller networks.  subprotocols The specialized protocols that work together and belong to a protocol suite.  switch The letters or words added to a command that allow you to customize a utility’s output. Switches are usually preceded by a hyphen or forward slash character.  TCP (Transmission Control Protocol) A core protocol of the TCP/IP suite. TCP belongs to the Transport layer and provides reliable data delivery services.  TCP/IP (Transmission Control Protocol/Internet Protocol) A suite of networking protocols that includes TCP, IP, UDP, and many others. TCP/IP provides the foundation for data exchange across the Internet.  TCP/IP core protocols The major subprotocols of the TCP/IP suite, including IP, TCP, and UDP.  Telnet A terminal emulation protocol used to log on to remote hosts using the TCP/IP protocol. Telnet resides in the Application layer of the OSI model.  TFTP (Trivial File Transfer Protocol) A TCP/IP Application layer protocol that enables file transfers between computers. Unlike FTP, TFTP relies on UDP at the Transport layer and does not require a user to log on to the remote host.  Time to Live See TTL.  TLD (top-level domain) The highest-level category used to distinguish domain names—for example, .org, .com, and .net. A TLD is also known as the domain suffix.  top-level domain See TLD.  Transmission Control Protocol See TCP.  Transmission Control Protocol/Internet Protocol See TCP/IP.  Trivial File Transfer Protocol See TFTP.  TTL (Time to Live) A number that indicates the maximum duration that a packet can remain on the network before it is discarded. Although this field was originally meant to represent units of time, on modern networks it represents the number of router hops a datagram has endured. The TTL for datagrams is variable and configurable, but is usually set at 32 or 64. Each time a datagram passes through a router, its TTL is reduced by 1.When a router receives a datagram with a TTL equal to 1, the router discards that datagram.  UDP (User Datagram Protocol) A core protocol in the TCP/IP suite that sits in the Transport layer of the OSI model. UDP is a connectionless transport service.  unicast address A type of IPv6 address that represents a single interface on a device. An IPv6 unicast address begins with either FFC0 or FF80.  User Datagram Protocol See UDP.  Well Known Ports The TCP/IP port numbers 0 to 1023, so named because they were long ago assigned by Internet authorities to popular services (for example, FTP and Telnet), and are, therefore, well known and frequently used.  Zero configuration See Zeroconf.  Zeroconf (Zero configuration) A collection of protocols that assigns link-local addresses, performs DNS functions, and discovers services, such as print services, available to the node.  zone file A text file associated with a DNS zone that contains resource records identifying domains and their IP addresses.  zone transfer In DNS, the act of copying a primary name server’s zone file to the secondary name server to ensure that both contain the same information. Chapter 5 Topologies and Ethernet Standards At a Glance Instructor’s Manual Table of Contents • Overview • Objectives • Teaching Tips • Quick Quizzes • Class Discussion Topics • Additional Projects • Additional Resources • Key Terms Lecture Notes Overview This chapter details some basic elements of network architecture: physical and logical topologies. These elements are crucial to understanding networking design, troubleshooting, and management. In this chapter, the student will also learn about the most commonly used network access method, Ethernet, including its many Physical layer standards. Chapter Objectives After reading this chapter and completing the exercises, the student will be able to: • Describe the basic and hybrid LAN physical topologies, and their uses, advantages, and disadvantages • Describe the backbone structures that form the foundation for most networks • Compare the different types of switching used in data transmission • Explain how nodes on Ethernet networks share a communications channel • Identify the characteristics of several Ethernet standards Teaching Tips Simple Physical Topologies 1. Define and describe the term physical topology. 2. Mention characteristics not included in the specification. 3. Identify three fundamental shapes: a. Bus b. Ring c. Star 4. Explain that these shapes may be mixed to create hybrid topologies. 5. Explain why students need to understand physical topologies. Bus 1. Introduce the bus topology. 2. Define and describe the term bus. 3. Describe the physical medium used by bus networks. 4. Define and describe a passive technology. 5. Explain what is meant by the term broadcast domain. 6. Define and describe terminators. 7. Define and explain signal bounce. 8. Explain why a bus network must be grounded at one end. 9. Use Figure 5-1 to illustrate a terminated bus network. 10. Discuss the advantage of bus networks. 11. Describe three disadvantages of bus networks. Ring 1. Introduce the ring topology. 2. Use Figure 5-2 to illustrate a typical ring topology network. 3. Explain how data is transmitted around the ring. 4. Define and describe an active technology. 5. Describe the physical medium used by ring networks. 6. Discuss two disadvantages of ring networks. Star 1. Introduce the star topology. 2. Use Figure 5-3 to illustrate a typical star topology network. 3. Discuss the physical medium used by star networks. 4. Explain how star networks are cabled. 5. Discuss disadvantages of star networks. 6. Explain the advantages of star networks. Teaching Tip Students may find more information at http://docwiki.cisco.com/wiki/Ethernet_Technologies Hybrid Topologies 1. Explain why pure bus, ring, or star topologies rarely exist. 2. Define a hybrid topology. Star-Wired Ring 1. Define and describe the star-wired ring. 2. Use Figure 5-4 to illustrate a star-wired ring hybrid physical topology. 3. Describe the benefits of star-wired ring hybrid physical topology. 4. Mention the networking technology that utilizes the star-wired ring physical topology. Star-Wired Bus 1. Define and describe the star-wired bus. 2. Use Figure 5-5 to illustrate a star-wired bus physical topology. 3. Describe the benefits of star-wired bus physical topology. 4. Mention the one drawback of star-wired bus physical topology. 5. Emphasize that the benefits outweigh the drawback. 6. Mention the networking technology that utilizes the star-wired bus physical topology. Logical Topologies 1. Introduce and describe logical topologies. 2. Emphasize that a network’s logical topology will not necessarily match its physical topology. 3. Define and describe the bus logical topology. 4. Define and describe the star logical topology. 5. Use Figure 5-4 to illustrate a star-wired ring hybrid physical topology where the signals follow a circular path, even as they travel through a connectivity device. Teaching Tip Students may find more information at: http://en.wikipedia.org/wiki/Network_topology#Logical_topology Backbone Networks 1. Introduce the concept of a network backbone. 2. Note the cabling needs for a network backbone and discuss why they are important. 3. Describe how organization size affects the make-up of a network backbone. 4. Introduce the shapes of network backbones. Serial Backbone 1. Define and explain the term serial backbone. 2. Define and explain the term daisy-chain. 3. Explain why star-wired hybrids are a logical solution for growth. 4. Explain why a LAN’s infrastructure can be expanded with little additional cost using this type of backbone. 5. Describe the devices that may be attached to a serial backbone. 6. Use Figure 5-6 to illustrate a serial backbone network. 7. Explain what happens if the backbone does not utilize hubs in a serial fashion. 8. Explain what happens if standards describing the maximum number of repeating devices allowed are not followed. Distributed Backbone 1. Define and explain the term distributed backbone. 2. Use Figure 5-7 to illustrate a simple distributed backbone. 3. Explain why a distributed backbone provides the benefits of simple expansion and limited capital outlay for growth. 4. Describe the make-up of a more complicated distributed backbone. 5. Use Figure 5-8 to illustrate a distributed backbone connecting multiple LANs. 6. Discuss the benefit of providing network administrators with the ability to segregate workgroups and, therefore, manage them more easily. 7. Discuss the benefit of adapting well to an enterprise-wide network confined to a single building. 8. Describe how distributed backbones may include hubs linked in a daisy-chain fashion and note the drawback this may present. 9. Note the drawback of the potential single points of failure. 10. Emphasize that distributed backbone network can be relatively simple, quick, and inexpensive. Collapsed Backbone 1. Define and explain the term collapsed backbone. 2. Use Figure 5-9 to illustrate a collapsed backbone. 3. Contrast Figure 5-9 with Figure 5-8. 4. Mention that a single router or switch is the highest layer of the backbone and describe its special requirements. 5. Explain why this is a risky configuration. 6. Explain why using a router may slow data transmission. 7. Describe the advantages of using a collapsed backbone. Parallel Backbone 1. Define and explain the term parallel backbone. 2. Use Figure 5-10 to illustrate a simple parallel backbone. 3. Describe the advantages of using a parallel backbone. 4. Describe the disadvantage of using a parallel backbone. 5. Note that the benefits outweigh the disadvantage. 6. Describe situations in which a parallel backbone is most appropriate. 7. Emphasize that an enterprise-wide LAN or WAN may include different combinations of simple physical topologies and backbone designs. Quick Quiz 1 1. True or False: A physical topology depicts a network in a narrow scope. Answer: False 2. Which physical topology consists of a single cable that connects all nodes on a network without intervening connectivity devices? a. star b. wired c. ring d. bus Answer: D 3. Most Ethernet networks are based on the ____ topology. a. star b. wired c. ring d. bus Answer: A 4. True or False: A logical topology is a characteristic of network transmission that reflects the way in which data is transmitted between nodes. Answer: True 5. A(n) ____ backbone is the simplest kind of backbone. Answer: serial Switching 1. Define and explain switching. 2. Introduce the three types of switching methods: a. Circuit switching b. Packet switching c. Multiprotocol label switching Circuit Switching 1. Define and explain circuit switching. 2. Discuss the disadvantages of circuit switching. 3. Describe applications that may benefit from circuit switching. Packet Switching 1. Define and explain packet switching. 2. Emphasize and explain why packets may travel any path on the network to reach the destination. 3. Explain characteristics of packets in packet switching. 4. Discuss the advantages of packet switching. 5. Provide examples of packet-switched networks. MPLS (Multiprotocol Label Switching) 1. Define and explain MPLS (Multiprotocol Label Switching) switching. 2. Explain why MPLS supports IP. 3. Emphasize that MPLS is more often used with Layer 2 protocols, such as those designed for WANs. 4. Discuss the benefits of MPLS. a. Include a discussion of how MPLS addresses some limitations of traditional packet switching. b. Use Figure 5-11 to illustrate MPLS shim within a frame. 5. Define QoS (quality of service) and explain how MPLS offers better guarantees than QoS. Teaching Tip Students may read more about QOS Quality of Service (QoS) at http://docwiki.cisco.com/wiki/Quality_of_Service_Networking Ethernet 1. Briefly review Ethernet’s history and its benefits. 2. Explain that Ethernet has evolved and improved through many variations. 3. Mention the one item all Ethernet networks have in common. CSMA/CD (Carrier Sense Multiple Access with Collision Detection) 1. Define a network access method. 2. Explain why a network access method is necessary. 3. Break down the acronyms CS and MA in CSMA/CD and explain their meanings. 4. Define and explain a collision. 5. Break down the acronym CD in CSMA/CD and explain its meaning. 6. Explain the purpose of a collision detection routine. 7. Define the term jamming and explain how it works. 8. Note that on heavily trafficked network segments, collisions are common and explain what happens in terms of collisions as these networks grow. 9. Point out the concept of “critical mass”. 10. Use Figure 5-12 to illustrate the way CSMA/CD regulates data flow to avoid and, if necessary, detect collisions. 11. Define and explain a collision domain. 12. Discuss Ethernet design considerations used to reduce collisions. 13. Mention the Ethernet cabling distance limitations used to reduce collisions. 14. Explain the differences between 100 or 1000 Mbps networks and 10 Mbps networks in terms of the number of segments and hubs. Ethernet Standards for Copper Cable 1. Remind students that the IEEE Physical layer standards specify how signals are transmitted to the media. 2. Point out that technologies described by IEEE standards differ significantly in how they encode signals at the Physical layer. 3. Describe the details that a network engineer needs to understand for designing networks and installing cable. 4. Explain the characteristics of 10Base-T. a. Use Figure 5-14 to illustrate a 10Base-T Ethernet network with maximum segment lengths. 5. Explain the characteristics of 100Base-T. a. Use Figure 5-15 to illustrate a 100Base-T Ethernet network. 6. Explain the characteristics of 1000Base-T. 7. Explain the characteristics of 10GBase-T. Ethernet Standards for Fiber-Optic Cable 1. Explain the characteristics of 100Base-FX. 2. Explain the characteristics of 1000Base-LX. 3. Explain the characteristics of 1000Base-SX. 10-Gigabit Fiber-Optic Standards 1. Remind students that the throughput potential for fiber-optic cable is extraordinary. 2. Point out that scientists continue to push its limits. 3. Introduce the IEEE 802.3ae standard for fiber-optic Ethernet networks transmitting data at 10 Gbps. 4. Explain the characteristics of 10GBase-SR and 10GBase-SW. 5. Explain the characteristics of 10GBase-LR and 10GBase-LW. 6. Explain the characteristics of 10GBase-ER and 10GBase-EW. Teaching Tip Students may read about Gigabit Ethernet at http://www.cisco.com/en/US/tech/tk389/tk214/tk277/tsd_technology_support_sub-protocol_home.html Summary of Common Ethernet Standards 1. Point out to the students that they must be familiar with the different characteristics and limitations of each type of network discussed in this chapter to obtain Network+ certification. 2. Use Table 5-1 to summarize the characteristics and limitations for common Physical layer networking standards, including Ethernet networks that use twisted pair cable and fiber-optic cable. Ethernet Frames 1. Remind students that data frames are the packages that carry higher-layer data and control information that enable data to reach their destinations without errors and in the correct sequence. 2. Introduce the four kinds of data frames Ethernet networks may use. 3. Explain why Ethernet frame types do not have a relation with the topology or cabling characteristics of the network. 4. Point out that framing takes place independently of the higher-level layers. 5. Emphasize that not all frame types are well suited to carry all kinds of traffic. Using and Configuring Frames 1. Remind students that a node’s Data Link layer services must be properly configured to expect the types of frames it might receive. 2. Explain why it is important for LAN administrators to ensure that all devices use the same, correct frame type. 3. Point out that virtually all networks use the Ethernet II frame type today. 4. Explain how frame types are typically specified. 5. Explain the terms autodetect and autosense. Frame Fields 6. Describe the fields that all Ethernet frame types have in common. 7. Explain how the minimum and maximum Ethernet frame sizes are determined. 8. Explain why larger frame sizes on a network generally result in faster throughput. 9. Discuss how to improve network performance by properly managing frames. Ethernet II (DIX) 1. Define and describe Ethernet II (DIX). 2. Explain why Ethernet II is the frame type most commonly used on contemporary Ethernet networks. a. Use Figure 5-17 to illustrate an Ethernet II (DIX) frame. PoE (Power over Ethernet) 1. Define PoE (Power over Ethernet). 2. Discuss the concept of carrying electrical power over Ethernet connections. 3. Introduce the two types of devices PoE requires and describe each device type. 4. Use Figure 5-18 to illustrate a PoE-capable switch. 5. Use Figure 5-19 to illustrate PoE adapters. Teaching Tip Students may find more information on IEEE Power over Ethernet standards at http://www.ieee802.org/3/af Quick Quiz 2 1. ____ is a component of a network’s logical topology that determines how connections are created between nodes. Answer: Switching 2. One thing all Ethernet networks have in common is their access method, known as ____. Answer: CSMA/CD 3. Fast Ethernet operates at ____. a. 10 Mbps b. 100 Mbps c. 1000 Mbps d. 10,000 Mbps Answer: B 4. Which IEEE standard applies to 10-Gigabit Fiber-Optic Standards? a. 802.3ae b. 802.3z c. 802.3u d. 802.3ab Answer: A 5. True or False: All frame types are well suited to carrying all kinds of traffic. Answer: False Class Discussion Topics 1. As a class, discuss the difference between a physical topology and a logical topology. Why are both necessary? 2. As a class, discuss whether there are too many Ethernet cabling standards today. Are they all necessary? Who really controls a standards acceptance: IEEE, vendors, customers, or others? Additional Projects 1. IEEE is looking ahead and working on standards for 100-Gigabit Ethernet. Have the students research this effort and provide a written report on the need for and status of the project. 2. Have each student research available PoE PSE (power sourcing equipment) and PDs (powered devices). The report should include a write-up for three to five devices for each type. Included in the write-up should be a description of the device, including the manufacturer, the model, the seller, the cost, and a summary of the manufacturer specifications. Additional Resources 1. IEEE 802.3 Power over Ethernet Plus Study Group http://www.ieee802.org/3/poep_study/index.html 2. Cisco Introduction to LAN Protocols http://docwiki.cisco.com/wiki/Introduction_to_LAN_Protocols 3. Ethernet Alliance http://www.ethernetalliance.org/ 4. IEEE 802.3 Ethernet Working Group http://www.ieee802.org/3/index.html Key Terms  10Base-T A Physical layer standard for networks that specifies baseband transmission, twisted pair media, and 10-Mbps throughput. 10Base-T networks have a maximum segment length of 100 meters and rely on a star topology.  10GBase-ER A Physical layer standard for achieving 10-Gbps data transmission over single-mode, fiber-optic cable. In 10GBase-ER, the ER stands for extended reach. This standard specifies a star topology and segment lengths up to 40,000 meters.  10GBase-EW A variation of the 10GBase-ER standard that is specially encoded to operate over SONET links.  10GBase-LR A Physical layer standard for achieving 10-Gbps data transmission over single-mode, fiber-optic cable using wavelengths of 1310 nanometers. In 10GBase-LR, the LR stands for long reach. This standard specifies a star topology and segment lengths up to 10,000 meters.  10GBase-LW A variation of the 10GBase-LR standard that is specially encoded to operate over SONET links.  10GBase-SR A Physical layer standard for achieving 10-Gbps data transmission over multimode fiber using wavelengths of 850 nanometers. The maximum segment length for 10GBase-SR can reach up to 300 meters, depending on the fiber core diameter and modal bandwidth used.  10GBase-SW A variation of the 10GBase-SR standard that is specially encoded to operate over SONET links.  10GBase-T A Physical layer standard for achieving 10-Gbps data transmission over twisted pair cable. Described in its 2006 standard 802.3an, IEEE specifies Cat 6 or Cat 7 cable as the appropriate medium for 10GBase-T. The maximum segment length for 10GBase-T is 100 meters.  100Base-FX A Physical layer standard for networks that specifies baseband transmission, multimode fiber cabling, and 100-Mbps throughput. 100Base-FX networks have a maximum segment length of 2000 meters. 100Base-FX may also be called Fast Ethernet.  100Base-T A Physical layer standard for networks that specifies baseband transmission, twisted pair cabling, and 100-Mbps throughput. 100Base-T networks have a maximum segment length of 100 meters and use the star topology. 100Base-T is also known as Fast Ethernet.  100Base-TX A type of 100Base-T network that uses two wire pairs in a twisted pair cable, but uses faster signaling to achieve 100-Mbps throughput. It is capable of full-duplex transmission and requires Cat 5 or better twisted pair media.  1000Base-LX A Physical layer standard for networks that specifies 1-Gbps transmission over fiber-optic cable using baseband transmission. 1000Base-LX can run on either single-mode or multimode fiber. The LX represents its reliance on long wavelengths of 1300 nanometers. 1000Base-LX can extend to 5000-meter segment lengths using single-mode, fiber-optic cable. 1000Base-LX networks can use one repeater between segments.  1000Base-SX A Physical layer standard for networks that specifies 1-Gbps transmission over fiber-optic cable using baseband transmission. 1000Base-SX runs on multimode fiber. Its maximum segment length is 550 meters. The SX represents its reliance on short wavelengths of 850 nanometers. 1000Base-SX can use one repeater.  1000Base-T A Physical layer standard for achieving 1 Gbps over UTP. 1000Base-T achieves its higher throughput by using all four pairs of wires in a Cat 5 or better twisted pair cable to both transmit and receive signals. 1000Base-T also uses a different data encoding scheme than that used by other UTP Physical layer specifications.  5-4-3 rule A guideline for 10-Mbps Ethernet networks stating that between two communicating nodes, the network cannot contain more than five network segments connected by four repeating devices, and no more than three of the segments may be populated.  802.3ab The IEEE standard that describes 1000Base-T, a 1-gigabit Ethernet technology that runs over four pairs of Cat 5 or better cable.  802.3ae The IEEE standard that describes 10-gigabit Ethernet technologies, including 10GBase-SR, 10GBase-SW, 10GBase-LR, 10GBase-LW, 10GBase-ER, and 10GBase-EW.  802.3af The IEEE standard that specifies a way of supplying electrical Power over Ethernet (PoE). 802.3af requires Cat 5 or better UTP or STP cabling and uses power sourcing equipment to supply current over a wire pair to powered devices. PoE is compatible with existing 10Base-T, 100Base-TX, 1000Base-T, and 10GBase-T implementations.  802.3an The IEEE standard that describes 10GBase-T, a 10-Gbps Ethernet technology that runs on Cat 6 or Cat 7 twisted pair cable.  802.3u The IEEE standard that describes Fast Ethernet technologies, including 100Base-TX.  802.3z The IEEE standard that describes 1000Base (or 1-gigabit) Ethernet technologies, including 1000Base-LX and 1000Base-SX.  access method A network’s method of controlling how nodes access the communications channel. For example, CSMA/CD (Carrier Sense Multiple Access with Collision Detection) is the access method specified in the IEEE 802.3 (Ethernet) standard.  active topology A topology in which each workstation participates in transmitting data over the network. A ring topology is considered an active topology.  broadcast domain Logically grouped network nodes that can communicate directly via broadcast transmissions. By default, switches and repeating devices such as hubs extend broadcast domains. Routers and other Layer 3 devices separate broadcast domains.  bus The single cable connecting all devices in a bus topology.  bus topology A topology in which a single cable connects all nodes on a network without intervening connectivity devices.  Carrier Ethernet A level of Ethernet service that is characterized by very high throughput and reliability and is used between carriers, such as NSPs.  Carrier Sense Multiple Access with Collision Detection See CSMA/CD.  circuit switching A type of switching in which a connection is established between two network nodes before they begin transmitting data. Bandwidth is dedicated to this connection and remains available until users terminate the communication between the two nodes.  collapsed backbone A type of backbone that uses a router or switch as the single central connection point for multiple subnetworks.  collision In Ethernet networks, the interference of one node’s data transmission with the data transmission of another node sharing the same segment.  collision domain The portion of an Ethernet network in which collisions could occur if two nodes transmit data at the same time. Switches and routers separate collision domains.  CSMA/CD (Carrier Sense Multiple Access with Collision Detection) A network access method specified for use by IEEE 802.3 (Ethernet) networks. In CSMA/CD, each node waits its turn before transmitting data to avoid interfering with other nodes’ transmissions. If a node’s NIC determines that its data have been involved in a collision, it immediately stops transmitting. Next, in a process called jamming, the NIC issues a special 32-bit sequence that indicates to the rest of the network nodes that its previous transmission was faulty and that those data frames are invalid. After waiting, the NIC determines if the line is again available; if it is available, the NIC retransmits its data.  daisy chain A group of connectivity devices linked together in a serial fashion.  data propagation delay The length of time data take to travel from one point on the segment to another point. On Ethernet networks, CSMA/CD’s collision detection routine cannot operate accurately if the data propagation delay is too long.  distributed backbone A type of backbone in which a number of intermediate connectivity devices are connected to one or more central connectivity devices, such switches or routers, in a hierarchy.  enterprise An entire organization, including local and remote offices, a mixture of computer systems, and a number of departments. Enterprise-wide computing takes into account the breadth and diversity of a large organization’s computer needs.  Ethernet II The original Ethernet frame type developed by Digital Equipment Corporation, Intel, and Xerox, before the IEEE began to standardize Ethernet. Ethernet II is distinguished from other Ethernet frame types in that it contains a 2-byte type field to identify the upper-layer protocol contained in the frame. It supports TCP/IP and other higher-layer protocols.  Fast Ethernet A type of Ethernet network that is capable of 100-Mbps throughput. 100Base-T and 100Base-FX are both examples of Fast Ethernet.  fault tolerance The capability for a component or system to continue functioning despite damage or malfunction.  Gigabit Ethernet A type of Ethernet network that is capable of 1000-Mbps, or 1-Gbps, throughput.  hybrid topology A physical topology that combines characteristics of more than one simple physical topology.  jamming A part of CSMA/CD in which, upon detecting a collision, a station issues a special 32-bit sequence to indicate to all nodes on an Ethernet segment that its previously transmitted frame has suffered a collision and should be considered faulty.  logical topology A characteristic of network transmission that reflects the way in which data are transmitted between nodes. A network’s logical topology may differ from its  physical topology. The most common logical topologies are bus and ring.  MPLS (multiprotocol label switching) A type of switching that enables any one of several Layer 2 protocols to carry multiple types of Layer 3 protocols. One of its benefits is the ability to use packet-switched technologies over traditionally circuit-switched networks. MPLS can also create end-to-end paths that act like circuit-switched connections.  modal bandwidth A measure of the highest frequency of signal a multimode fiber-optic cable can support over a specific distance. Modal bandwidth is measured in MHz-km.  multiprotocol label switching See MPLS.  packet switching A type of switching in which data are broken into packets before being transported. In packet switching, packets can travel any path on the network to their destination because each packet contains a destination address and sequencing information.  padding The bytes added to the data (or information) portion of an Ethernet frame to ensure this field is at least 46 bytes in size. Padding has no effect on the data carried by the frame.  parallel backbone A type of backbone that consists of more than one connection from the central router or switch to each network segment.  passive topology A network topology in which each node passively listens for, then accepts, data directed to it. A bus topology is considered a passive topology.  PD (powered device) On a network using Power over Ethernet, a node that receives power from power sourcing equipment.  physical topology The physical layout of the media, nodes, and devices on a network. A physical topology does not specify device types, connectivity methods, or addressing schemes. Physical topologies are categorized into three fundamental shapes: bus, ring, and star. These shapes can be mixed to create hybrid topologies.  PoE (Power over Ethernet) A method of delivering current to devices using Ethernet connection cables.  Power over Ethernet See PoE.  power sourcing equipment See PSE.  powered device See PD.  preamble The field in an Ethernet frame that signals to the receiving node that data are incoming and indicates when the data flow is about to begin.  PSE (power sourcing equipment) On a network using Power over Ethernet, the device that supplies power to end nodes.  QoS (quality of service) The result of specifications for guaranteeing data delivery within a certain period of time after their transmission.  quality of service See QoS.  ring topology A network layout in which each node is connected to the two nearest nodes so that the entire network forms a circle. Data are transmitted in one direction around the ring. Each workstation accepts and responds to packets addressed to it, then forwards the other packets to the next workstation in the ring.  serial backbone A type of backbone that consists of two or more internetworking devices connected to each other by a single cable in a daisy chain.  SFD (start-of-frame delimiter) A 1-byte field that indicates where the data field begins in an Ethernet frame.  signal bounce A phenomenon, caused by improper termination on a bus-topology network, in which signals travel endlessly between the two ends of the network, preventing new signals from getting through.  star topology A physical topology in which every node on the network is connected through a central connectivity device. Any single physical wire on a star network connects only two devices, so a cabling problem will affect only two nodes. Nodes transmit data to the device, which then retransmits the data to the rest of the network segment where the destination node can pick it up.  star-wired bus topology A hybrid topology in which groups of workstations are connected in a star fashion to connectivity devices that are networked via a single bus.  star-wired ring topology A hybrid topology that uses the physical layout of a star and the token-passing data transmission method.  start-of-frame delimiter See SFD.  switching A component of a network’s logical topology that manages how packets are filtered and forwarded between nodes on the network.  terminator A resistor that is attached to each end of a bus-topology network and that causes the signal to stop rather than reflect back toward its source. Chapter 6 Network Hardware, Switching, and Routing At a Glance Instructor’s Manual Table of Contents • Overview • Objectives • Teaching Tips • Quick Quizzes • Class Discussion Topics • Additional Projects • Additional Resources • Key Terms Lecture Notes Overview Students need to understand how data arrives at its destination. In data networks, the task of directing information efficiently to the correct destination is handled by hubs, routers, bridges, and switches. In this chapter, students will learn about these devices and their roles in managing data traffic. Material in this chapter relates mostly to functions occurring in the Data Link and Network layers of the OSI model. Some material also relates to the Physical layer. Students will learn the concepts involved in moving data from place to place, including issues related to switching and routing protocols. Students will also see pictures of the hardware - hubs, switches, bridges, and routers - that make data transfer possible. In addition, students will learn all about network interface cards, which serve as the workstation’s link to the network and are often the source of connectivity problems. Chapter Objectives After reading this chapter and completing the exercises, the student will be able to: • Identify the functions of LAN connectivity hardware • Install, configure, and differentiate between network devices such as, NICs, hubs, bridges, switches, routers, and gateways • Explain the advanced features of a switch and understand popular switching techniques, including VLAN management • Explain the purposes and properties of routing • Describe common IPv4 and IPv6 routing protocols Teaching Tips NICs (Network Interface Cards) 1. Define and describe NICs (network interface cards). 2. Point out that nearly all NICs contain a data transceiver. 3. Explain why NICs belong to both the Physical layer and Data Link layer of the OSI model. 4. Describe how advances in NIC technology are making NICs smarter than ever. 5. Emphasize that NICs do not analyze information added by the protocols in Layers 3 through 7 of the OSI model. 6. Explain why it is important to understand NICs. Types of NICs 1. Explain what a student should know before ordering or installing a NIC. 2. Describe dependencies of NICs. 3. Explain that NICs vary in the following ways: a. Access method (for example, Ethernet) b. Network transmission speed (for example, 100 Mbps versus 1 Gbps) c. Connector interfaces (for example, RJ-45 versus SC) d. Number of connector interfaces, or ports e. Method of interfacing with the computer’s motherboard (for example, on-board, expansion slot, or peripheral) and interface standard (for example, PCIe or USB) f. Manufacturer (popular NIC manufacturers include 3Com, Adaptec, D-Link, IBM, Intel, Kingston, Linksys, Netgear, SMC, and Western Digital, to name just a few) g. Support for enhanced features, such as PoE, buffering, or traffic management 4. Introduce the Internal Bus Standards category of NICs that are installed on an expansion board inside a computer. 5. Define and describe the term bus. 6. Define and describe the term expansion slot. 7. Define and describe the term expansion card. 8. Point out that multiple bus types exist. 9. Note that to become part of a computer’s bus, an expansion board must use the same bus type. 10. Introduce and describe the PCI bus type. 11. Describe the older ISA bus type and compare PCI to ISA. 12. Introduce and describe the PCIe bus type. 13. Describe the advantages of PCIe over PCI. 14. Explain how the PCIe slots differ from PCI slots. Include a discussion on PCIe lanes. 15. Use Figure 6-1 to illustrate a PCIe NIC. 16. Explain how to determine the type of bus a PC uses. 17. Use Figure 6-3 to illustrate a motherboard with multiple expansion slots. 18. Explain how to determine the best NIC for a PC if the PC motherboard supports more than one kind of expansion slot. 19. Introduce the Peripheral Bus Standards category of NICs that are installed externally. a. PCMCIA (Personal Computer Memory Card International Association) b. USB (universal serial bus) c. CompactFlash d. FireWire (IEEE 1394) 20. Explain the Personal Computer Memory Card International Association’s role in setting standards for peripheral devices. a. PC Card b. CardBus c. ExpressCard 21. Describe the peripheral PCMCIA standard called PC Card. 22. Describe the peripheral PCMCIA standard called CardBus. 23. Describe the peripheral PCMCIA standard called ExpressCard. 24. Introduce and describe the USB peripheral bus standard. 25. Introduce and describe the Firewire peripheral bus standard. 26. Introduce and describe the CompactFlash peripheral bus standard. 27. Introduce and describe the on-board peripheral bus standard. 28. Introduce and describe the wireless peripheral bus standard. Teaching Tip Students may find more information on how buses work at http://computer.howstuffworks.com/computer-buses-channel.htm Teaching Tip Students may find more information on PCMCIA and Linux at http://pcmcia-cs.sourceforge.net Teaching Tip Students may find more information on PCMCIA/PC Card and CardBus frequently asked questions at http://www.sycard.com/pcard_qa.html Installing and Configuring NICs 1. Describe the three general steps to install a NIC: a. Install NIC hardware b. Install NIC software c. Configure NIC 2. Explain how to install and configure expansion card NIC hardware. 3. Use Figure 6-4 to illustrate a properly installed NIC. 4. Explain how to install a PCMCIA-standard NIC into a laptop. 5. Explain how to install and configure expansion card NIC software. 6. Define the term device driver. 7. Explain how drivers are installed on purchased computers and computer with new hardware added. 8. Note that most operating systems come with a multitude of built-in device drivers. 9. Emphasize that if the operating system cannot find a driver for the new hardware, the driver will have to be installed and configured using NIC software and the operating system interface. 10. Explain how to install NIC software from a Windows 7 interface. 11. Use Figure 6-5 to illustrate the Windows Network Connection dialog box. 12. Describe how a student may interpret NIC LED indicators to verify NIC functionality after installation. 13. Define and explain CMOS. 14. Define and explain BIOS. 15. Introduce and explain firmware settings. 16. Explain how to change firmware. Include a discussion on configuration the NIC configuration utility. 17. Describe how to perform diagnostics with the NIC configuration utility. a. Define and describe a loopback plug, b. Describe a loopback test. Teaching Tip Demonstrate the availability modern Linksys network adapters utilizing various bus types by navigating to the Linksys adapter’s product page at http://homestore.cisco.com/en-us/products/linksys-other-adapters_stcVVcatId552067VVviewcat.htm Quick Quiz 1 1. True or False: A NIC has no room for a transceiver. Answer: False 2. A bus is defined by ____. a. data path speed b. pin size c. data path width and clock speed d. data path width and pin size Answer: C 3. True or False: One disadvantage to using wireless NICs is that currently they are somewhat more expensive than wire-bound NICs using the same bus type. Answer: True 4. ____ is a set of data or instructions that has been saved to a ROM. Answer: Firmware 5. If the ___ NIC LED indicator light is blinking, this indicates that the NIC is functional and transmitting frames to the network. a. ACT b. LNK c. TX d. RX Answer: C Modular Interfaces 1. Explain the advantages of using a modular interface for a network interface. 2. Define and describe a GBIC. 3. Define and describe the SFP GBIC. 4. Use Figures 6-7 and 6-8 to illustrate a copper and fiber optic GBIC. Repeaters and Hubs 1. Define and describe a repeater. 2. Define and describe a hub. 3. Describe how placement of hubs in a network design can vary. 4. Emphasize that dozens of types of hubs exist and explain how they vary. 5. Point out that hubs have mostly been replaced by switches or routers and explain why. Teaching Tip Demonstrate the availability modern Linksys network routers by navigating to the Linksys router product page at: http://homestore.cisco.com/en-us/products/linksys_stcVVcatId551966VVviewcat.htm Bridges 1. Define and describe bridges. 2. Explain the advantage of using bridges over repeaters and hubs. 3. Explain the disadvantage of using bridges. 4. Explain how a bridge translates data between two segment types. 5. Use Figure 6-10 to illustrate a bridge’s use of a filtering database. 6. Point out that after bridge installation, several methods may be used to learn about the network and discover the destination address for each packet it handles. 7. Emphasize that bridges are nearly extinct and explain why. Teaching Tip Demonstrate the availability modern Linksys network bridges by navigating to the Linksys bridge product page at: http://homestore.cisco.com/Linksys-Powerline_stcVVcatId554690VVviewcat.htm Switches 1. Define and describe switches. 2. Emphasize why switches can interpret MAC address information. 3. Note the components within switches. 4. Discuss multiport switches and their advantages over a bridge. 5. Use Figure 6-11 to illustrate switches. 6. Discuss how switches have been used historically. 7. Describe the disadvantages of switches, noting that some network administrators have replaced backbone routers with switches. Switch Installation 1. Explain the best way to ensure that a switch is installed properly. 2. Review the general steps for installing a switch. 3. Use Figure 6-12 to illustrate how to connect a workstation to a switch. 4. Use Figure 6-13 to illustrate a switch on a small network. Switching Methods 1. Introduce switching methods. 2. Define and describe the cut-through mode switching method. 3. Describe the advantages and disadvantages of the cut-through method, as well as where it is best implemented. 4. Define and describe the store-and-forward mode switching method. 5. Describe the advantages and disadvantages of the store-and-forward mode, as well as where it is best implemented. Teaching Tip Demonstrate the availability modern Linksys network switches by navigating to the Linksys bridge product page at: http://homestore.cisco.com/en-us/products/linksys-other-routers_stcVVcatId552066VVviewcat.htm Teaching Tip Students may find more information on how switches work at: http://computer.howstuffworks.com/lan-switch.htm VLANs and Trunking 1. Define a VLAN (virtual local area networks). 2. Define the term broadcast domain. 3. Define the term collision domain and contrast it with a broadcast domain. 4. Use Figure 6-14 to illustrate a simple VLAN design. 5. Describe the advantages and reasons for using a VLAN. 6. Explain how to create and maintain a VLAN. 7. Emphasize the critical step in creating the VLAN. 8. Use Figure 6-15 to illustrate the result of the show vlans command on a Cisco switch. 9. Discuss potential useful situation for VLANs. 10. Define the term trunking. 11. Define the term trunk. 12. Explain the advantages of VLAN trunking. 13. Note considerations in VLAN configuration planning. Teaching Tip Students may find more information on Understanding VLAN Trunk Protocol (VTP) from Cisco at: http://www.cisco.com/en/US/tech/tk389/tk689/technologies_tech_note09186a0080094c52.shtml STP (Spanning Tree Protocol) 1. Introduce and define STP (Spanning Tree Protocol). 2. Use Figure 6-17 to illustrate an enterprise-wide switched network requiring STP. 3. Review the three steps STP performs. 4. Use Figure 6-18 to illustrate STP-selected paths on a switched network. 5. Review the history of STP. 6. Discuss the newer protocol as well as the proprietary protocols. 7. Emphasize that when installing switches on your network, you do not need to enable or configure STP (or the more current version that came with your switch). Content and Multilayer Switches 1. Define a Layer 3 switch. 2. Define a Layer 4 switch. 3. Define a content switch. 4. Describe the advantages and disadvantages of these types of switches. 5. Note that distinguishing factors between Layer 3 and Layer 4 switches are manufacturer dependent. 6. Discuss higher layer switches and their use. Routers 1. Define and describe a router. Router Characteristics and Functions 1. Explain the strength of routers. 2. Emphasize that routers are indispensible in large WAN and LANs like the Internet. 3. Describe the components in a router. 4. Define and describe a modular router. 5. Note the use of inexpensive routers in the home and small office. 6. Use Figure 6-19 to illustrate three routers. 7. Describe the tasks performed by routers. 8. Describe the optional functions a router may contain. 9. Describe the two methods of directing network traffic: a. Static routing b. Dynamic routing 10. Describe the installation characteristics of small networks and large networks. 11. Use Figure 6-20 to illustrate the placement of routers on a LAN. Routing Protocols 1. Define and describe the term best path. 2. Describe a routing protocol. 3. Define and describe router convergence time. 4. Introduce distance-vector routing protocols. 5. Explain how the RIP (Routing Information Protocol) works. 6. Explain how RIPv2 (Routing Information Protocol version 2) works. 7. Explain how BGP (Border Gateway Protocol) works. 8. Introduce link-state routing protocols. 9. Explain how OSPF (Open Shortest Path First) works. 10. Explain how IS-IS (Intermediate System to Intermediate System) works. 11. Introduce the concept of hybrid routing protocols. 12. Explain how the EIGRP (Enhanced Interior Gateway Routing Protocol) works. Gateways and Other Multifunction Devices 1. Define and describe gateways. 2. Discuss popular gateways. Teaching Tip Students may find more information on gateway protocols at: http://www.cisco.com/en/US/tech/tk1077/tsd_technology_support_protocol_home.html Quick Quiz 2 1. True or False: Repeaters operate in the Physical layer of the OSI model. Answer: True 2. True or False: Bridges are protocol independent. Answer: True 3. Switches that operate anywhere between Layer 4 and Layer 7 are also known as ____or application switches. Answer: content switches 4. ____ is a technique in which a network administrator programs a router to use specific paths between nodes. Answer: Static routing 5. A gateway must operate at ____ of the OSI model. a. multiple layers b. Layer 2 c. Layer 3 d. Layers 4-7 Answer: A Class Discussion Topics 1. Wireless technology is widely deployed in the modern network. Have students discuss some of the most recent changes or developments in the wireless networking field and the impact of those changes on the network overall. For example, is it necessary to potentially reengineer parts of the network to support a migration to more wireless or wire-free type of network? 2. Many students will most likely have a small home network or know someone who does. Have student describe the communications devices in these networks. Are they wireless or wired? Are there routers, switches, or hubs? Describe experiences, good and bad, with these networks. Additional Projects 1. Have each student research available routers. The report should include a write-up for three to five devices. Included in the write-up should be a description of the device, including the manufacturer, the model, the seller, the cost, and a summary of the manufacturer specifications. 2. Have students research the EIGRP routing protocol in more depth. The student should provide a report, including sections on: Introduction, Background and History, Technical Specifications, Implementation, Barriers, and Summary. Additional Resources 1. PCMCIA Official Web site http://www.pcmcia.org/ 2. PCI Special Interest Group http://www.pcisig.com/home 3. USB (Universal Serial Bus) Implementer's Forum http://www.usb.org/home 4. CompactFlash Association http://www.compactflash.org 5. CiscoPress Sample Chapter on VLANs and Trunking http://www.ciscopress.com/articles/article.asp?p=29803 6. Cisco router information http://www.cisco.com/en/US/products/hw/routers/index.html Key Terms  802.1D The IEEE standard that describes, among other things, bridging and STP (Spanning Tree Protocol).  802.1q The IEEE standard that specifies how VLAN and trunking information appear in frames and how switches and bridges interpret that information.  802.1w The IEEE standard that describes RSTP (Rapid Spanning Tree Protocol), which evolved from STP (Spanning Tree Protocol).  access port The interface on a switch used for an end node. Devices connected to access ports are unaware of VLAN information.  application switch A switch that provides functions between Layer 4 and Layer 7 of the OSI model.  backplane A synonym for motherboard, often used in the context of switches and routers.  best path The most efficient route from one node on a network to another. Under optimal network conditions, the best path is the most direct path between two points. However, when traffic congestion, segment failures, and other factors create obstacles, the most direct path might not be the best path.  BGP (Border Gateway Protocol) A distance-vector routing protocol capable of considering many factors in its routing metrics. BGP, an Exterior Gateway Protocol, is the routing protocol used on Internet backbones.  BID (Bridge ID) A combination of a 2-byte priority field and a bridge’s MAC address, used in STP (Spanning Tree Protocol) to select a root bridge.  Border Gateway Protocol See BGP.  border router A router that connects an autonomous LAN with an exterior network—for example, the router that connects a business to its ISP.  bridge A connectivity device that operates at the Data Link layer (Layer 2) of the OSI model and reads header information to forward packets according to their MAC addresses. Bridges use a filtering database to determine which packets to discard and which to forward. Bridges contain one input and one output port and separate network segments.  Bridge ID See BID.  bus The type of circuit used by a computer’s motherboard to transmit data to components. Most new Pentium computers use buses capable of exchanging 32 or 64 bits of data. As the number of bits of data a bus handles increases, so too does the speed of the device attached to the bus.  content switch A switch that provides functions between Layer 4 and Layer 7 of the OSI model.  convergence time The time it takes for a router to recognize a best path in the event of a change or network outage.  cost In the context of routing metrics, the value assigned to a particular route as judged by the network administrator. The more desirable the path, the lower its cost.  cut-through mode A switching mode in which a switch reads a frame’s header and decides where to forward the data before it receives the entire packet. Cut-through mode is faster, but less accurate, than the other switching method, store-and-forward mode.  device driver The software that enables an attached device to communicate with the computer’s operating system.  distance-vector The simplest type of routing protocols, these determine the best route for data based on the distance to a destination. Some distance-vector routing protocols, like RIP, only factor in the number of hops to the destination, while others take into account latency and other network traffic characteristics.  driver See device driver.  dynamic routing A method of routing that automatically calculates the best path between two nodes and accumulates this information in a routing table. If congestion or failures affect the network, a router using dynamic routing can detect the problems and reroute data through a different path. Modern networks primarily use dynamic routing.  EGP (Exterior Gateway Protocol) A routing protocol that can span multiple, autonomous networks. BGP and EIGRP are examples of Exterior Gateway Protocols.  EIGRP (Enhanced Interior Gateway Routing Protocol) A routing protocol developed in the mid-1980s by Cisco Systems that has a fast convergence time and a low network overhead, but is easier to configure and less CPU-intensive than OSPF. EIGRP also offers the benefits of supporting multiple protocols and limiting unnecessary network traffic between routers.  Enhanced Interior Gateway Routing Protocol See EIGRP.  ethtool A popular tool for viewing and modifying network interface properties on Linux computers.  expansion board A circuit board used to connect a device to a computer’s motherboard.  expansion card See expansion board.  expansion slot A receptacle on a computer’s motherboard that contains multiple electrical contacts into which an expansion board can be inserted.  Exterior Gateway Protocol See EGP.  exterior router A router that directs data between nodes outside a given autonomous LAN, for example, routers used on the Internet’s backbone.  filtering database A collection of data created and used by a bridge that correlates the MAC addresses of connected workstations with their locations. A filtering database is also known as a forwarding table.  firewall A device (either a router or a computer running special software) that selectively filters or blocks traffic between networks. Firewalls are commonly used to improve data security.  forwarding table See filtering database.  gateway A combination of networking hardware and software that connects two dissimilar kinds of networks. Gateways perform connectivity, session management, and data translation, so they must operate at multiple layers of the OSI model.  gateway router See border router.  GBIC (Gigabit interface converter) A standard type of modular interface designed in the 1990s for Gigabit Ethernet connections. GBICs may contain RJ-45 or fiber-optic cable ports (such as LC, SC, or ST). They are inserted into a socket on a connectivity device’s backplane.  Gigabit interface converter See GBIC.  hot-swappable The feature of a component that allows it to be installed or removed without disrupting operations.  hub A connectivity device that retransmits incoming data signals to its multiple ports. Typically, hubs contain one uplink port, which is used to connect to a network’s backbone.  IGP (Interior Gateway Protocol) A routing protocol, such as RIP, that can only route data within an autonomous (internal) network.  interior router A router that directs data between nodes on an autonomous LAN.  Intermediate System to Intermediate System See IS-IS.  Interior Gateway Protocol See IGP.  IS-IS (Intermediate System to Intermediate System) A link-state routing protocol that uses a best-path algorithm similar to OSPF’s. IS-IS was originally codified by ISO, which referred to routers as “intermediate systems,” thus the protocol’s name. Unlike OSPF, IS-IS is designed for use on interior routers only.  Layer 3 switch A switch capable of interpreting data at Layer 3 (Network layer) of the OSI model.  Layer 4 switch A switch capable of interpreting data at Layer 4 (Transport layer) of the OSI model.  link-state A type of routing protocol that enables routers across a network to share information, after which each router can independently map the network and determine the best path between itself and a packet’s destination node.  loopback adapter See loopback plug.  loopback plug A connector used for troubleshooting that plugs into a port (for example, a serial, parallel, or RJ-45 port) and crosses over the transmit line to the receive line, allowing outgoing signals to be redirected back into the computer for testing.  main bus See bus.  mini GBIC See SFP.  on-board NIC A NIC that is integrated into a computer’s motherboard, rather than connected via an expansion slot or peripheral bus.  on-board port A port that is integrated into a computer’s motherboard.  Open Shortest Path First See OSPF.  OSPF (Open Shortest Path First) A routing protocol that makes up for some of the limitations of RIP and can coexist with RIP on a network.  PCIe (PCI Component Interconnect Express) A 32-bit bus standard capable of transferring data at up to 1 Gbps per data path, or lane, in full-duplex transmission. PCIe is commonly used for expansion board NICs.  PCI Component Interconnect Express See PCIe.  Rapid Spanning Tree Protocol See RSTP.  RIP (Routing Information Protocol) The oldest routing protocol that is still widely used, RIP is a distance-vector protocol that uses hop count as its routing metric and allows up to only 15 hops. It is considered an IGP. Compared with other, more modern, routing protocols, RIP is slower and less secure.  RIPv2 (Routing Information Protocol version 2) An updated version of the original RIP routing protocol, which makes up for some of its predecessor’s overhead and security flaws. However, RIPv2’s packet forwarding is still limited to a maximum 15 hops.  root bridge The single bridge on a network selected by the Spanning Tree Protocol to provide the basis for all subsequent path calculations.  router A multiport device that operates at Layer 3 of the OSI model and uses logical addressing information to direct data between networks or segments. Routers can connect dissimilar LANs and WANs running at different transmission speeds and using a variety of Network layer protocols. They determine the best path between nodes based on traffic congestion, available versus unavailable routes, load balancing targets, and other factors.  Routing Information Protocol See RIP.  Routing Information Protocol version 2 See RIPv2.  routing metric The method used by routing protocols to determine the best path for data to follow over a network. Routing metrics may be calculated using any of several variables, including number of hops, bandwidth, delay, MTU, cost, and load.  routing protocols The means by which routers communicate with each other about network status. Routing protocols determine the best path for data to take between nodes.  routing switch See Layer 3 switch.  routing table A database stored in a router’s memory that maintains information about the location of hosts and best paths for forwarding packets to them.  RSTP (Rapid Spanning Tree Protocol) As described in IEEE’s 802.1w standard, a version of the Spanning Tree Protocol that can detect and correct for network changes much more quickly.  runt An erroneously shortened packet.  SFP (small form-factor pluggable) transceiver A standard hot-swappable network interface used to link a connectivity device’s backplane with fiber-optic or copper cabling. SFPs are known as mini GBICs because they perform a similar function as GBICs, but have a smaller profile. Current SFP standards enable them to send and receive data at up to 10 Gbps.  SFP GBIC See SFP.  Spanning Tree Protocol See STP.  static routing A technique in which a network administrator programs a router to use specific paths between nodes. Because it does not account for occasional network congestion, failed connections, or device moves and requires manual configuration, static routing is not optimal.  store-and-forward mode A method of switching in which a switch reads the entire data frame into its memory and checks it for accuracy before transmitting it. Although this method is more time consuming than the cut-through method, it allows store-and-forward switches to transmit data more accurately.  STP (Spanning Tree Protocol) A switching protocol defined in IEEE 802.1D. STP operates in the Data Link layer to prevent traffic loops by calculating paths that avoid potential loops and by artificially blocking links that would complete a loop. Given changes to a network’s links or devices, STP recalculates its paths.  switch A connectivity device that logically subdivides a network into smaller, individual collision domains. A switch operates at the Data Link layer of the OSI model and can interpret MAC address information to determine whether to filter (discard) or forward packets it receives.  system bus See bus.  trunk port The interface on a switch capable of managing traffic from multiple VLANs.  trunking The aggregation of multiple logical connections in one physical connection between connectivity devices. In the case of VLANs, a trunk allows two switches to manage and exchange data between multiple VLANs.  uplink port A port on a connectivity device, such as a hub or switch, used to connect it to another connectivity device.  virtual local area network See VLAN.  VLAN (virtual local area network) A network within a network that is logically defined by grouping its devices’ switch ports in the same broadcast domain. A VLAN can consist of any type of network node in any geographic location and can incorporate nodes connected to different switches.  VLAN trunking protocol See VTP.  VTP (VLAN trunking protocol) Cisco’s protocol for exchanging VLAN information over trunks. VTP allows one switch on a network to centrally manage all VLANs. Instructor Manual for Network+ Guide to Networks Tamara Dean 9781133608196, 9781133608257, 9781337569330