CompTIA Network+ Guide to Networks 9th Edition (1) (1).pdf

2 CompTIA Network+ Guide to Networks I notified my supervisor who contacted the construction team to see if it could be corrected. In the meantime, I labeled the cable in the patch panel and at the wall so that if/when there were issues again, the cable could be easily identified. Je...

2 CompTIA Network+ Guide to Networks I notified my supervisor who contacted the construction team to see if it could be corrected. In the meantime, I labeled the cable in the patch panel and at the wall so that if/when there were issues again, the cable could be easily identified. Jeffery Johnson Technology Support Specialist Georgia Northwestern Technical College Loosely defined, a network is a group of computers and other devices (such as printers) that are connected by some type of transmission media. Variations on the elements of a network and the way it is designed, however, are nearly ­infinite. A network can be as small as two computers connected by a cable in a home office or the most complex network of all, the Internet, made up of billions of computers and other devices connected across the world via a combination of cable, phone lines, and wireless links. Networks might link smartphones, personal computers, main- frame computers, printers, corporate phone systems, security cameras, vehicles, and wearable technology devices. They might communicate through copper wires, fiber-optic cable, or radio waves. This module introduces you to the fundamentals of networks and how technicians support them. Network Models ✔ Certification 1.2 Explain the characteristics of network topologies and network types. Average reading time: 15 minutes A topology describes how the parts of a whole work together. When studying networking, you need to understand both the physical topology and the logical topology of a network, as follows: Physical topology—Mostly refers to a network’s hardware and how computers, other devices, and cables or radio signals work together to form the physical network Logical topology—Mostly refers to how software controls access to network resources (including how users and software initially gain access to the network) and how specific resources such as applications and data- bases are shared on the network Exam The CompTIA Network1 exam objectives are developed by industry professionals and cover the concepts and skills they know will be most helpful to you in working with a network. The competency and scope Tip reflect what you would likely learn in about 9–12 months of hands-on experience in a junior network administrator or network support technician job role. These Network1 Exam Tip boxes call your attention to specific concepts known to be commonly tested on the Network1 exam. For example, the Network1 exam expects you to understand the difference between a physical network diagram and a logical net- work diagram, and the purpose each serves. You might be given a scenario that includes a physical or logical network diagram, and you will need to interpret the information given in that diagram to answer the related question(s). As you read through the text, take a moment to consider the tips given in each of these Network1 Exam Tip boxes to determine whether you understand the material at the level indicated. Let’s begin with a discussion of network models that will help you understand logical topologies and how computers relate to one another in a network. Later in this module, you’ll learn about network hardware and physical topologies. Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.  Module 1 Introduction to Networking 3 Controlling how users and programs get access to resources on a network is a function of the operating systems used on the network. Each OS (operating system) is configured to use one of two models to connect to network resources: the peer-to-peer model or the client-server model. The peer-to-peer model can be achieved using any assort- ment of desktop, mobile, or tablet operating systems, but the client-server model requires a NOS (network operating system), which controls access to the entire network. Examples include Windows Server 2019, Ubuntu Server, and Red Hat Enterprise Linux (Ubuntu and Red Hat are versions of Linux). Applying Concepts 1-1: Explore Network Operating Systems It’s easier to understand what a network operating system is if you’ve seen one or two in action. For each of the NOSs listed previously (Windows Server 2019, Ubuntu Server, and Red Hat Enterprise Linux), use your favorite search engine to complete the following steps: 1. Search for information about the NOS and write down a short description based on your findings. Include a few features and advantages and identify who develops and publishes each NOS. 2. Search for images of screenshots for the NOS. What are some major elements that you notice on these screens? How are these NOSs managed? 3. Find one or two introductory videos for each NOS and watch the videos. What are some similarities between each NOS? What are some of the differences? Note 1-1 Windows Server 2019, Ubuntu Server, and Red Hat Enterprise Linux are all examples of a specific kind of NOS called a server operating system. Other kinds of NOSs exist. For example, network devices such as routers and switches require a NOS that might also be called networking software and are typically managed through a CLI (command-line interface). Examples include IOS (Internetwork OS) on Cisco devices and Junos OS on Juniper devices. You might also refer to other kinds of software, such as a hypervisor that runs virtualized devices or a cloud platform that hosts cloud-based resources, as a type of NOS. You’ll learn more about all these platforms throughout this course. Peer-to-Peer Network Model In a P2P (peer-to-peer) network model, the operating system of each computer on the network is responsible for controlling access to its resources without centralized control. The computers, called nodes or hosts on the network, form a logical group of computers and users that share resources (see Figure 1-1). Each computer on a P2P network controls its own administration, resources, and security. Examples of operating systems that might be installed on computers in a peer-to-peer network are Windows, Linux, macOS, or Chrome OS on desktop and laptop computers and iOS, Android, or Chrome OS on mobile devices. Note 1-2 When looking at the diagrams in Figure 1-1 and later in Figure 1-2, keep in mind that the connecting lines describe the logical arrangement or topology of the group of computers, as opposed to the physical arrangement. The physical arrange- ment in both diagrams may be the same, but the method the OSs use to logically connect the devices differs. The term physical topology refers to a network’s hardware and how devices and cables fit together. The term logical topology refers to the way software controls access to network resources and how those resources are shared on the network. Devices in a peer-to-peer network can share resources through various techniques of file sharing or user accounts. Most OSs offer options for sharing files with peered devices, even if those devices are running differ- ent OSs. If all computers in a peer-to-peer network are running a Windows operating system, resources can be Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 4 CompTIA Network+ Guide to Networks Ubuntu Desktop Windows 10 macOS Scanner Network printer Figure 1-1 In a peer-to-peer network, no computer has more authority than another; each computer controls its own resources and communicates directly with other computers shared using Windows folder and file sharing or a Windows workgroup. In both Note 1-3 cases, each computer maintains a list of users and their rights on that computer. This course assumes you have Windows allows a user on the network to access local resources based on these mastered the knowledge and assigned rights. You can combine folder and file sharing with workgroups on the skills covered in the CompTIA same network and even using the same computers. However, it can get confusing A1 certification objectives. to accurately track permissions in this case, so it’s best to stick with either folder Using and supporting work- and file sharing or workgroups. groups and sharing folders and Generally, if the network supports fewer than about 15 computers, a peer-to- files are part of this content. If peer network is the way to go. The following are advantages of using peer-to-peer you need to learn how folder networks: and file sharing and work- groups are configured and sup- They are simple to configure. For this reason, they may be used in environ- ported, see CompTIA A1 Guide ments in which time or technical expertise is scarce. to IT Technical Support by Jean They are often less expensive to set up and maintain than other types of Andrews, Joy Dark, and Jill West. networks. A network operating system, such as Windows Server 2019, is much more expensive than a desktop operating system, such as Windows 10. The following are disadvantages of using traditional peer-to-peer networks: They are not scalable, which means, as a peer-to-peer network grows larger, adding or changing significant elements of the network may be difficult. They are not necessarily secure, meaning that in simple installations, data and other resources shared by network users can be easily discovered and used by unauthorized people. They are not practical for connecting more than a few computers because it’s too time consuming to manage the resources on the network. For example, suppose you want to set up a file server using P2P file sharing. A server is any computer or program that provides a service, such as data or other resources, to other devices. A file server stores files for other computers to access. On this file server, you create a folder named \Shared- Docs and create 20 user accounts, one for each of 20 users who need access to the folder. Then you must set up the workstations with the same user accounts, and the password to each user account on the workstation must match the password for the matching user account on the file server. It can be an organizational night- mare to keep it all straight! If you need to manage that many users and shared resources, it’s probably best to implement Windows Server or another NOS. Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.  Module 1 Introduction to Networking 5 Client-Server Network Model In the client-server network model (which is sometimes called the client-server architecture or client-server topol- ogy), resources are managed by the NOS via a centralized directory database (see Figure 1-2). The database can be managed by one or more servers, so long as they each have a similar NOS installed. Chromebook Windows 10 Network printer Windows Server domain controller Domain database (Active Directory) macOS Ubuntu Desktop Local printer Scanner Figure 1-2 A  Windows domain uses the client-server model to control access to the network, where security on each computer or device is controlled by a centralized database on a domain controller When Windows Server controls network access to a group of computers, this logical group is called a Windows domain. The centralized directory database that contains user account information and security for the entire group of computers is called AD (Active Directory). Each user on the network has their own domain-level account assigned by the network administrator and kept in Active Directory. This account might be a local account, which is specific to that domain, or a Microsoft account, which links local domain resources with Microsoft cloud resources. A user can sign on to the network from any computer on the network and get access to the resources that Active Directory allows. This process is managed by AD DS (Active Directory Domain Services). A computer making a request from another is called the client. Clients on a client-server network can run applica- tions installed on the desktop and store their own data on local storage devices. Clients don’t share their resources directly with each other; instead, access is controlled by entries in the centralized domain database. A client computer accesses resources on another computer by way of the servers controlling this database. In summary, the NOS (for example, Windows Server 2019, Ubuntu Server, or Red Hat Enterprise Linux) is respon- sible for the following: Managing data and other resources for clients Ensuring that only authorized users access the network Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 6 CompTIA Network+ Guide to Networks Controlling which types of files a user can open and read Restricting when and from where users can access the network Dictating which rules computers will use to communicate In some situations, supplying applications and data files to clients Servers that have a NOS installed require more memory, processing power, and storage capacity than clients because servers must handle heavy processing loads and requests from multiple clients. For example, a server might use a RAID (redundant array of independent disks) configuration of hard drives, so that if one hard drive fails, another hard drive automatically takes its place. Although client-server networks are typically more complex in their design and maintenance than peer-to-peer networks, they offer many advantages over peer-to-peer networks, including the following: User accounts and passwords to the network are assigned in one place. Access to multiple shared resources (such as data files or printers) can be centrally granted to a single user or groups of users. Problems on the network can be monitored, diagnosed, and often fixed from one location. Client-server networks are more scalable than peer-to-peer networks. In other words, it’s easier to add users and devices to a client-server network. Now that you have a basic understanding of what a network operating system is and the foundational role it plays, you’re ready to look at some of the applications involved in managing the data that travels on a network. These appli- cations allow network devices to establish connections with each other and carry out various tasks. Remember this… Compare physical topology with logical topology. Describe a client-server network model in contrast with a peer-to-peer network model. Explain the role of AD (Active Directory) in a Windows domain. Self-check 1. Which of the following is part of a network’s physical topology? a. A network server’s operating system b. A printer plugged into a nearby desktop computer c. Password for the wireless network d. File permission settings on a desktop computer 2. Which of the following is an advantage of P2P file sharing? a. Scalable b. Centrally controlled c. Secure d. Inexpensive 3. What group must clients join to access network resources in a client-server network? a. Workgroup b. Domain c. Peer group d. RAID Check your answers at the end of this module. Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.  Module 1 Introduction to Networking 7 You’re Ready You’re now ready to complete Project 1-1: IT and Networking Certifications, or you can wait until you’ve finished reading this module. Client-Server Applications ✔ Certification 1.5 Explain common ports and protocols, their application, and encrypted alternatives. Average reading time: 9 minutes The resources a network makes available to its users include applications and the data provided by these applications. Collectively, these resources are usually referred to as network services. In this section, you’ll focus on applications typically found on most networks. These applications involve at least two endpoint devices, such as computers or smartphones, and are known as client-server applications. The first computer, a client computer, requests data or a service from the second computer, which is the server. For example, in Figure 1-3, someone uses a web browser to request a web page from a web server. Note that the two computers do not have to reside on the same network—they can communicate across connected networks like the Internet. Web server Web server sends Web browser requests (cengage.com) requested page cengage.com/index.html Web page The Internet index.html Figure 1-3 A  web browser (client application) requests a web page from a web server (server application); the web server returns the requested data to the client Network Services and Their Protocols How does the client know how to make the request in a way the server can understand and respond to? These net- worked devices use methods and rules for communication known as protocols. To handle the request for a web page, the client computer must first find the web server. Then, the client and server must agree on the protocols they will use to communicate. Finally, the client makes the request, and the server sends its response in the form of a web page. Hardware, the operating systems, and the applications on both computers are all involved in this process. The computers on a network communicate with each other via the protocols they have in common. The two pri- mary network protocols are TCP (Transmission Control Protocol) and IP (Internet Protocol), and the suite of all the protocols an OS uses for communication on a network is the TCP/IP suite of protocols. Here’s a brief list of several popular client-server applications and their protocols used on networks and the Inter- net; you’ll study many of these protocols more closely in later modules: Web service—A web server serves up web pages to clients. Many corporations have their own web servers, which are available privately on the corporate network. Other web servers are public, accessible from anywhere on the Internet. The primary protocol used by web servers and browsers (clients) is HTTP (Hypertext Transfer Protocol). Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 8 CompTIA Network+ Guide to Networks When HTTP is layered on top of an encryption protocol, such as SSL (Secure Sockets Layer) or TLS (Transport Layer Security), the result is HTTPS (HTTP Secure), which gives a secure transmission. The most popular web server applications are Apache (see apache.org) and Nginx (pronounced engine-x, see nginx.com), both of which are free and open source and primarily run on Linux systems. Open source is the term for software whose code is publicly available for use and modification. Open source applications are often considered more secure because users can evaluate the source code of the software to ensure there are no loopholes left open for attackers to exploit. Note that “open source” is not synonymous with “free,” but in this case, Apache and Nginx happen to be both free and open source. Another popular choice is IIS (Internet Information Services), which is embedded in the Windows Server operating system. Note 1-4 To verify that a web-based transmission is secure, look for “https” in the URL in the browser address box, as in https:// www.cengage.com. Also look for a padlock icon, such as the one shown in Figure 1-4. Padlock icon Figure 1-4 The lock icon indicates the web page is using HTTPS Email services—Email is a client-server application that involves two servers. The client uses SMTP (Simple Mail Transfer Protocol) to send an email message to the first server, which is sometimes called the SMTP server (see Figure 1-5). The first server sends the message on to the receiver’s mail server, where it’s stored until the recipient requests delivery. The recipient’s mail server delivers the message to the receiving client using one of two protocols: POP3 (Post Office Protocol, version 3) or IMAP4 (Internet Message Access Protocol, ­version 4). Using POP3, email is downloaded to the client computer and typically removed from the server. Using IMAP4, the client application manages the email while it remains stored on the server. Both these protocols are available over SSL or TLS for security. An example of a popular email server application is Microsoft Exchange Server. Outlook, an application in the Microsoft Office suite of applications, is a popular email client application. Sender SMTP Sender’s mail server SMTP Receiver POP3 or IMAP4 Receiver’s mail server Figure 1-5 S MTP is used to send email to a recipient’s email server, and POP3 or IMAP4 is used by the client to receive email DNS service—DNS (Domain Name System) helps clients find web servers over a network such as the Internet. Often, companies will run their own DNS servers, especially for their employees’ computers to find resources Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.  Module 1 Introduction to Networking 9 within the corporate network. Internet providers also run DNS services for Note 1-5 their customers, and many public DNS servers, such as Google’s, are available for anyone to use. An encrypted and secure FTP service—FTP service is a client-server application that transfers files file transfer protocol is SFTP between two computers, and it primarily uses FTP (File Transfer Protocol). (Secure File Transfer Pro- FTP does not provide encryption and is, therefore, not secure. Web browsers tocol) , which is based on the can work as FTP clients, although dedicated FTP client applications, such as SSH protocol. SSH is discussed FileZilla (filezilla-project.org) and CuteFTP by Globalscape (globalscape.com/ below. cuteftp), offer more features for file transfer than does a browser. Database services—Not all data is stored in individual files. Databases serve as a container for massive amounts of data that can be organized into tables and records. Users and applications can then access and interact with the data that is stored on a database server. A DBMS (database management system) is software installed on the database server. It is responsible for making requested changes to the data and organizing the data for view- ing, reporting, or exporting. Many DBMSs use the programming language SQL (Structured Query Language, pronounced S-Q-L or just sequel) to configure and interact with the database’s objects and data. Popular exam- ples of SQL database software include Microsoft SQL Server, Oracle Database, and the open-source MySQL. Remote access service—Some protocols allow an administrator or other user to “remote in,” that is, to access a remote computer from the technician’s local device to control the computer remotely, as shown in Figure 1-6. The Telnet protocol is a command-line application included in many operating systems, but transmissions in Telnet are not encrypted. This has caused Telnet to be largely replaced by other, more secure programs, such as the ssh command in the Linux operating system. The ssh command in Linux uses the SSH (Secure Shell) protocol, which creates an encrypted channel or tunnel between two computers and provides security that Telnet lacks. In Windows operating systems, RDP (Remote Desktop Protocol) also provides secure, encrypted transmissions. SSH or RDP might be used when a vendor supports software on your corporate network. The vendor’s support technician at the vendor’s site Note 1-6 can connect to a computer on your corporate network and troubleshoot prob- Because they can be accessed lems with the vendor’s installed software. The corporate computer “serves from outside the local network, up” its desktop or command line, from which the technician can access any remote access servers necessi- resources on your corporate network. In this situation, the vendor’s computer tate strict security measures. is the client, and the corporate computer is the server or host. Desktop of local (client) computer Desktop of remote (host) computer Hard drive of the remote computer Other available networked devices Figure 1-6 U  sing Remote Desktop, you can access the desktop of the remote computer from your local computer Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 10 CompTIA Network+ Guide to Networks You can think of applications and their data as the payload traveling on a network and the operating systems as the traffic controllers managing the traffic. The road system itself is the hardware on which the traffic flows. Let’s look now at the basics of this networking hardware and the physical topologies they use. Remember this… Explain the purposes of various network services. Identify important network protocols. Notice the key role that encryption protocols play in securing other protocols. Distinguish between the functions of various email protocols. Identify common DBMSs. Self-check 4. Which of the following is a secure protocol? a. FTP b. HTTP c. Telnet d. SSH 5. What is an example of an open source DBMS? a. MySQL b. Microsoft SQL Server c. TCP/IP suite d. Oracle Database 6. Which of these protocols could not be used to access a server in a nearby building? a. Telnet b. RDP c. TLS d. SSH Check your answers at the end of this module. Network Hardware ✔ Certification 1.2 Explain the characteristics of network topologies and network types. 2.1 Compare and contrast various devices, their features, and their appropriate placement on the network. Average reading time: 13 minutes Technically, two computers connected by an ad hoc Wi-Fi connection are a network. But let’s start this discussion of networking hardware with the slightly more complex network shown in Figure 1-7. Keep in mind that every node on a network needs a network address so that other nodes can find it. Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.  Module 1 Introduction to Networking 11 Note 1-7 Notice the two printers in ­Figure 1-7. A network printer has a network port and connects directly to the switch. A local printer connects to a computer on the network. Windows 10 Chromebook Network printer Windows Server 2019 Switch macOS Ubuntu Desktop Local printer Scanner Figure 1-7 T his LAN has five computers, a network printer, a local printer, a scanner, and a switch, and uses a star topology LANs and Their Hardware The network in Figure 1-7 is a LAN (local area network) because each node on the network can communicate directly with others on the network. LANs are usually contained in a small space, such as an office or building. The five comput- ers and the network printer all connect to the switch by way of wired connections. A switch (see Figure 1-8) receives Vtls/Shutterstock.com Source: Juniper Networks, Inc. Shutterstock.com Mischa Gossen/ Figure 1-8 Industrial-grade and consumer-grade switches Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 12 CompTIA Network+ Guide to Networks incoming data from one of its ports and redirects (or switches) it to another port or multiple ports that will send the data to its intended destination(s) within the local network. The physical topology used by this network is called a star topology because all devices connect to one central device, the switch. Compare this to the physical topology of the net- work shown earlier in Figure 1-1 where each device connects to multiple other devices, which is called a mesh topology. Legacy Networking: Hubs A hub is an inefficient and outdated networking device that has been replaced by switches. A hub accepted signals from a transmitting device and repeated those signals to all other connected devices in a broadcast fashion. On Ethernet networks, hubs once served as the central connection point for a star topology. On today’s Ethernet networks, switches have now replaced hubs. Traffic is greatly reduced with switches because, when a switch receives a transmission from a device, the switch sends it only to the destination device or devices rather than broadcasting to all devices connected to the switch. Exam The CompTIA Network1 exam objectives include some older, legacy technologies because, in the real world, not all networks are fully updated. As a network technician, you should be prepared to manage Tip both older and newer technology. And on the exam, you should be ready to identify the benefits offered by newer technology. Studying the historical progression of some technologies can help you better under- stand modern technology, its benefits, and its limitations. Computers, network printers, switches, and other network devices have network ports into which you plug a network cable. A network port can be an onboard network port embedded in the computer’s motherboard, such as the port on the laptop in Figure 1-9. Another type of port is provided by a modular NIC (network interface card), also called a network adapter (see Figure 1-10), installed in an expansion slot on the motherboard. In reality, whether embedded on a motherboard or attached to an expansion slot, both ports are typically called NICs. Network port Figure 1-9 A  laptop provides an onboard network port to connect to a wired network A LAN can have several switches. For example, the network in Figure 1-11 has three switches daisy-chained together. The two thick, yellow lines in the figure connecting the three switches represent the backbone of this network. A backbone is a central conduit that connects the segments (pieces) of a network and is sometimes referred to as “a network of networks.” The backbone might use higher transmission speeds and different cabling than network cables connected to computers because of the heavier traffic and the longer distances it might span. Because the three switches are daisy-chained together in a single line, the network is said to use a bus topology. However, each switch is connected to its computers via a star topology. Therefore, the topology of the network in Figure 1-11 combines topologies and is called a hybrid topology. Alternatively, a central switch could connect to multiple peripheral switches that each connect to computers in their areas. The network in Figure 1-12 uses a star topology for the switches and also for the computers connected to each switch. In this case, the central switch is referred to as the hub and each peripheral switch is a spoke. Together, this network illustrates an example of a hub-and-spoke topology. Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.  Module 1 Introduction to Networking 13 MAC address Figure 1-10 T his Intel Gigabit Ethernet adapter, also called a network interface card or NIC, uses a PCIe x1 slot on a motherboard Network backbone Figure 1-11 This local network has three switches and is using a hybrid topology Figure 1-12 Switches connected in a hub-and-spoke topology Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 14 CompTIA Network+ Guide to Networks Legacy Networking: Ring Topology In addition to the star, mesh, bus, and hybrid topologies, the CompTIA Network1 exam expects you to know about the ring topology, which is seldom used today. In a ring topology, nodes are connected in a ring, with one node connecting only to its two neighboring nodes (see Figure 1-13). A node can put data on the ring only when it holds a token, which is a small group of bits passed around the ring. This is similar to saying “I hold the token, so I get to talk now.” The ring topology is rarely used today, primarily because of its slow speed and its vulnerability to failure. If one node fails, the entire ring fails. Ring Figure 1-13 U  sing a ring topology, a computer connects to the two computers adjacent to it in the ring A LAN needs a way to communicate with other networks, and that’s the purpose of a router. A router is a device that manages traffic between two or more networks and can help find the best path for traffic to get from one network to another. In SOHO (small office-home office) networks, which typically have fewer than 10 computers, a consumer- grade router is used to connect the LAN to the Internet (see Figure 1-14a). Note 1-8 A home network might use a combination device, which is both a router and a switch, and perhaps a wireless access point that creates a Wi-Fi hotspot. For example, the device might provide three network ports and a Wi-Fi hotspot that are part of the local network and one network port to connect to the network belonging to the ISP (Internet service provider) and on to the Internet. In this situation (see Figure 1-14b), the three ports for the local network are provided by a switch embedded in the device. The home router belongs to the home’s network on one side and the ISP’s network on the other. Don’t confuse this combo device with a dedicated router device in which each port connects to a different LAN. The key difference here is that a switch belongs to a single LAN, while a router belongs to multiple LANs. An enterprise or industrial-grade router can have several network ports, one for each of the networks it connects to. In that case, the router belongs to each of these networks. For example, in Figure 1-15, the router connects three LANs and has a network address that belongs to Network A, another network address that belongs to Network B, and a third network address for Network C. The fundamental difference between a switch and a router is that a switch belongs only to its local network and a router belongs to two or more networks—the router acts as a gateway between multiple networks, but a switch (even if there are multiple switches) can only communicate within a single network. Recall that nodes on a local network communicate directly with one another. However, a node on one LAN cannot communicate with a node on another LAN without a router to manage that communication and to stand as a gateway between the networks. In fact, routers are often referred to as “gateway devices” or just “gateways.” Now that you understand the basic functions of switches and routers, you’re ready to make the distinction between the two terms host and node. A host is any endpoint device, such as a computer or printer, connected to a network Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.  Module 1 Introduction to Networking 15 (a) Internet Switch Home router (b) Internet 1234 Combo device Figure 1-14 (a) A router stands between the LAN and the Internet, connecting the two networks; (b) Home networks often use a combo device that works as both a switch and a router Network A Router Network C Network B Figure 1-15 Three LANs connected by a router Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 16 CompTIA Network+ Guide to Networks that hosts or accesses a resource such as an application or data. A node is any device, such as a router or switch, connected to a network that can be addressed on the local network or managed through a network connection. A client computer or server is both a node and a host, but a router or switch does not normally host resources and is, therefore, merely a node on the network through which network traffic passes. A significant distinction here is that hosts are typically networked devices—that is, endpoint devices connected to the network to access or provide resources, such as a file server, smartphone, smart thermostat, security camera, or network printer. Cisco standards call these end devices. A node that is not a host, such as a router or switch, is a networking device—that is, a device that enables connections on the network but does not, itself, provide applications or data resources for networked devices to access. Cisco calls these intermediary devices. Hosts are end devices (also called endpoint devices), and nodes can be either end devices or intermediary devices. So far, you’ve already learned a great deal about local networks, called LANs. What about networks outside the local network? Let’s look at other types of networks, which primarily vary according to the geographic space and the specific connection technologies they use. WAN MANs and WANs A group of LANs that spread over a wide geographical area is called a WAN MAN (wide area network). A group of ­connected LANs in the same geographi- cal area—for example, a handful of government offices surrounding a state CAN capitol ­building—is known as a MAN (metropolitan area network) or CAN (campus area network), although in reality you won’t often see those terms used or they might be used interchangeably. WANs and MANs often LAN use different transmission methods and media than LANs do. The Internet is the largest and most varied WAN in the world. A much smaller network PAN type is a PAN (personal area network), which is a network of personal devices, such as the network you use when you sync your smartphone and your computer. Figure 1-16 shows the relative sizes of each of these common network types. Note that these are not drawn to scale—a PAN Figure 1-16 R  elative sizes of WAN, could cover a very small space (a few inches), while a WAN could cover MAN, CAN, LAN, and the entire world! PAN networks Figure 1-17 shows a WAN link between two LANs bound by routers. For example, a corporation might have an office in San Francisco and another in Philadelphia. Each office has a LAN, and a WAN link connects the two LANs. The WAN link is most likely provided by a third-party service provider and spans multiple physical network links to traverse the networks between the two cities. Other network types exist, such as the following: BAN (body area network)—Made up of personal fitness devices like a smartwatch, fitness tracker, AR (aug- mented reality) headset, AI (artificial intelligence) hearing aid, or other wearable devices. SAN (storage area network)—Consists of high capacity data storage devices in a distinctly defined network segment. WLAN (wireless local area network)—Consists of two or more devices connected wirelessly. You’ll learn more about WANs, SANs, and WLANs in later modules. In the meantime, let’s look at how the operating systems, applications, and hardware you’ve been studying here work together to create and manage a network and its resources. Remember this… Compare various network topologies, such as PAN, LAN, and WAN. Describe common network types and their characteristics. Identify and compare the primary devices used to create a network. Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.  Module 1 Introduction to Networking 17 San Francisco router Philadelphia router WAN LAN A LAN B Figure 1-17 A WAN connects two LANs in different geographical areas Self-check 7. When you connect your keyboard, mouse, and monitor to your computer, what kind of network topology are you using? a. Bus topology b. Mesh topology c. Star topology d. Ring topology 8. Which networking device is best for connecting your network printer to three computers? a. Switch b. Hub c. Router d. File server 9. Which network types can your smartphone use? a. WAN b. LAN c. PAN d. WAN and LAN e. WAN, LAN, and PAN Check your answers at the end of this module. Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 18 CompTIA Network+ Guide to Networks You’re Ready You’re now ready to complete Project 1-2: Explore Network Types on a Smartphone, or you can wait until you’ve finished reading this module. The Seven-Layer OSI Model ✔ Certification 1.1 Compare and contrast the Open Systems Interconnection (OSI) model layers and encapsulation concepts. 2.1 Compare and contrast various devices, their features, and their appropriate placement on the network. Average reading time: 21 minutes Recall that an application, such as a browser, depends on the operating system to communicate across the net- work. Operating systems, meanwhile, depend on hardware to communicate across the network (see the left side of Figure 1-18). Throughout the entire process, protocols govern each layer of communication. Browser Web server Browser Web server Operating system Operating system Operating system Operating system Hardware Hardware Hardware Hardware Cabling and other network hardware Cabling and other network hardware Figure 1-18 A  browser and web server communicate by way of the operating system and hardware, similar to how a letter is sent through the mail using the U.S. Postal Service and the road system To get a better sense of how this works, it’s helpful to think of a different type of communication: two people com- municating by way of the U.S. Postal Service (see the right side of Figure 1-18). The sender depends on the mailbox to hold their letter until a postal worker picks it up and takes it to the post office. The people at the post office, in turn, depend on truck drivers to transport the letter to the correct city. The truck drivers, for their part, depend on the road system. Throughout the entire process, various protocols govern how people behave. For example, the sender follows basic rules for writing business letters, the mail carriers follow U.S. Postal Service regulations for processing the mail, and the truck drivers follow traffic laws. Think of how complex it might be to explain to someone all the different rules or protocols involved if you were not able to separate or categorize these activities into layers. Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.  Module 1 Introduction to Networking 19 Applications Applications World Email FTP Wide Web 7. Application layer TCP/IP suite of protocols embedded in the OS HTTP SMTP FTP 6. Presentation layer Operating system HTTPS POP, IMAP FTPS 5. Session layer 4. Transport layer TCP or UDP 3. Network layer IP, ICMP, and ARP 2. Data link layer Hardware and hardware protocols Hardware Ethernet, Wi-Fi 1. Physical layer Figure 1-19 H  ow software, protocols, and hardware map to the seven-layer OSI model Early in the evolution of networking, a seven-layer model was developed to categorize the layers of network com- munication. This model, which is called the OSI (Open Systems Interconnection) reference model, is illustrated on the left side of Figure 1-19. It was first developed by the International Organization for Standardization, also called the ISO. (Its shortened name, ISO, is derived from a Greek word meaning equal.) Network engineers, hardware techni- cians, programmers, and network administrators still use the layers of the OSI model to communicate about network- ing technologies. In this course, you’ll learn to use the OSI model to help you understand networking protocols and troubleshoot network problems. Exam The CompTIA Network1 exam expects you to know how to apply the OSI model when troubleshooting Tip network problems. As you study various protocols used in networking, it will help tremendously to map each protocol onto the OSI model. By doing so, you’ll better understand the logistics of which software program or device is initiating and/or receiving the protocol or data and how other protocols are relating to it. Now let’s take a brief look at each layer in the OSI model. The layers are numbered in descending order, starting with layer 7, the application layer, at the top. Figure 1-19 guides you through the layers. Note 1-9 You need to memorize the seven layers of the OSI model. Here’s a seven-word, top-to-bottom mnemonic that can help: All People Seem To Need Data Processing (Application, Presentation, Session, Transport, Network, Data link, and Physi- cal). A bottom-to-top mnemonic is Please Do Not Throw Sausage Pizza Away (Physical, Data link, Network, Transport, Session, Presentation, and Application). You can also create your own! Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 20 CompTIA Network+ Guide to Networks Layer 7: Application Layer The application layer in the OSI model does not contain applications themselves, such as a 7 Application web browser, but instead describes the interface between two applications, each on separate 6 Presentation 5 Session computers. Earlier in this module, you learned about several protocols used at this layer, 4 Transport including HTTP, SMTP, POP3, IMAP4, DNS, FTP, Telnet, SSH, and RDP. Application layer proto- 3 Network cols are used by applications that fall into two categories: 2 Data Link 1 Physical Applications that provide services to a user, such as a browser and web server using the HTTP application layer protocol Utilities that provide services to the system, such as SNMP (Simple Network Management Protocol) pro- grams that monitor and gather information about network traffic and can alert network administrators about adverse conditions that need attention Data that is passed between applications or utility programs and the operating system is called a payload and includes control information. The two end-system computers that initiate sending and receiving data are called hosts. Layer 6: Presentation Layer In the OSI model, the presentation layer is responsible for reformatting, compressing, and/or 7 Application encrypting data in a way that the application on the receiving end can read. For example, an 6 Presentation 5 Session email message can be encrypted at the presentation layer by the email client or by the operat- 4 Transport ing system. 3 Network 2 Data Link Layer 5: Session Layer 1 Physical The session layer of the OSI model describes how data between applications is synced and 7 Application recovered if messages don’t arrive intact at the receiving application. For example, the Zoom 6 Presentation application works with the operating system to establish and maintain a session between two 5 Session 4 Transport endpoints for as long as a voice conversation or video conference is in progress. 3 Network The application, presentation, and session layers are so intertwined that, in practice, it’s 2 Data Link often difficult to distinguish between them. Also, tasks for each layer may be performed by the 1 Physical operating system or the application. Most tasks are performed by the OS when an application makes an API call to the OS. In general, an API (application programming interface) is an access point into a software’s available processes such that a specific type of request will generate a particular kind of response. An API call in this case, then, is the method an application uses when it makes a request of the OS. Layer 4: Transport Layer The transport layer is responsible for transporting application layer payloads from one applica- 7 Application tion to another. The two main transport layer protocols are TCP, which guarantees delivery, and 6 Presentation UDP, which does not, as described next: 5 Session 4 Transport TCP (Transmission Control Protocol)—Makes a connection with the end host, checks 3 Network whether the data is received, and resends it if it is not. TCP is, therefore, called a connec- 2 Data Link tion-oriented protocol. TCP is used by applications such as web browsers and email. 1 Physical Guaranteed delivery takes longer and is used when it is important to know that the data reached its destination. UDP (User Datagram Protocol)—Does not guarantee delivery because it doesn’t maintain a connection to check whether data is received; thus, UDP is called a connectionless protocol or best-effort protocol. UDP is used for broadcasting, such as streaming video or audio over the web, where guaranteed delivery is not as important as fast transmission. UDP is also used to monitor network traffic. Transport-layer protocols add control information in an area at the beginning of the payload called the header to create a message ready to be handed down to the network layer. The process of adding a header to the data inherited Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.  Module 1 Introduction to Networking 21 from the layer above is called encapsulation, which is kind of the same concept as putting a letter in an envelope. The transport layer header addresses the receiving application by a number called a port. If the message is too large to transport in one package across the network, TCP divides it into smaller messages called segments, and in UDP, they’re called datagrams. In the post office analogy, think of a message as a letter. The sender puts the letter in an envelope and adds the name of the sender and receiver, similar to how the transport layer encapsulates the payload into a segment or datagram that identifies both the sending and destination applications. However, this letter needs more addressing information, not just the names of the sender and receiver. That’s the job of lower OSI layers. Layer 3: Network Layer The network layer, sometimes called the Internet layer, is responsible for moving messages 7 Application from one node to another until they reach the destination host. This is the layer where routers 6 Presentation typically function. The principal protocol used by the network layer is IP (Internet Protocol). 5 Session IP adds its own network layer header to the segment or datagram, and the entire network layer 4 Transport 3 Network message is now called a packet. The network layer header identifies the sending and receiving 2 Data Link hosts by their IP addresses. An IP address is an address assigned to each node on a network, 1 Physical which the network layer uses to uniquely identify them across multiple networks. In the post office analogy, the network layer would be the trucking system used by the post office and the IP addresses would be the full return and destination addresses written on the envelope. IP relies on several supporting protocols to find the best route for a packet when traversing several networks on its way to its destination. These supporting protocols include ICMP (Internet Control Message Protocol) and ARP (Address Resolution Protocol). You’ll learn more about these protocols later. Along the way, if a network layer protocol is aware that a packet is larger than the maximum size allowed for its network, it will divide the packet into smaller packets in a process called fragmentation. Layer 2: Data Link Layer Layers 2 and 1 are responsible for interfacing with the physical hardware on the local network. 7 Application The protocols at these layers are programmed into the firmware of a computer’s NIC and other 6 Presentation networking hardware. Layer 2, the data link layer, is also commonly called the link layer. The 5 Session type of networking hardware or technology used on a network determines the data link layer 4 Transport 3 Network protocol used. Examples of data link layer protocols are Ethernet and Wi-Fi. Ethernet is used by 2 Data Link switches on wired networks and Wi-Fi is used by access points for wireless networks. As you’ll 1 Physical learn in later modules, several types of switches exist. The least intelligent (nonprogrammable) switches, which are called data link layer switches or layer 2 switches, operate only at this layer. More sophisticated switches might combine layer 2 functions with higher-layer functions and are called layer 3 switches. Note 1-10 The term firmware refers to programs embedded into hardware devices. This software does not change unless a firm- ware upgrade is performed. The data link layer puts its own control information in a data link layer header and also attaches control informa- tion to the end of the packet in a trailer. The entire data link layer message is then called a frame. The frame header contains the hardware addresses of the source and destination NICs. This address is called a MAC (Media Access Control) address, physical address, hardware address, or data link layer address and is embedded on every network adapter on the globe (refer back to Figure 1-10). These physical addresses are short-range addresses used only to find nodes on the local network. In the post office analogy, a truck might travel from one post office to the next en route to its final destination. The address of a post office along the route would be similar to the physical address of each device’s NIC that a frame reaches as it traverses each LAN on its way to its destination. Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 22 CompTIA Network+ Guide to Networks Layer 1: Physical Layer Layer 1, the physical layer, is responsible for sending bits via a wired or wireless transmis- 7 Application sion. These bits can be transmitted as wavelengths in the air (for example, Wi-Fi), voltage on a 6 Presentation copper wire (for example, Ethernet on twisted-pair cabling), or light (for example, Ethernet on 5 Session 4 Transport fiber-optic cabling). 3 Network It’s interesting to consider that the higher layers of the OSI model work the same for both 2 Data Link wired and wireless transmissions. In fact, the only layers that must deal with the details of wired 1 Physical versus wireless transmissions are the data link layer and physical layer on the firmware of the NIC. In the post office analogy, the data link and physical layers compare with the various road systems a postal truck might use, each with its own speed limits and traffic rules, and any flight systems a postal air- plane might use, with its own processes and flight traffic control. Whether a package stays on the ground or spends some time on a plane, the addressing rules for the sender and receiver remain the same. Protocol Data Unit or PDU As you’ve read, there are several different names for a group of bits as it moves from one layer to the next and from one LAN to the next. Although technicians loosely call this group of bits a message or a transmission, the techni- cal name regardless of layer is PDU (protocol data unit). Table 1-1 can help you keep straight all these names for each layer. Table 1-1 Names for a PDU or message as it moves from one layer to another OSI model Name Technical name Layer 7, application layer Payload or data L7PDU Layer 6, presentation layer Layer 5, session layer Layer 4, transport layer Segment (TCP) or datagram (UDP) L4PDU Layer 3, network layer Packet L3PDU Layer 2, data link layer Frame L2PDU Layer 1, physical layer Bit or transmission L1PDU Summary of How the Layers Work Together Now let’s tie the layers together with the simple example shown in Figure 1-20. This transmission involves a browser and web server on their respective hosts, a switch, and a router. As you follow the red line from browser to web server, notice the sending host encapsulates the payload in headers and a trailer before sending it, much like an assistant would place the boss’s business letter in an envelope before putting it in the mail. On the other end, the receiving host removes the headers and trailer in reverse order before the message reaches the web server application, just as the receiver’s assistant would remove the letter from the envelope before handing it to the recipient. Removing a header and trailer from a lower layer’s PDU is called decapsulation. Note 1-11 In conceptual drawings and network maps, symbols are used for switches and routers. In the figure, notice the square symbol representing a switch and the round symbol representing a router. Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.  Module 1 Introduction to Networking 23 7 Application Browser Switch 6 Presentation 5 Session P Payload 2 Data link H H H P T Frame 4 Transport H P Segment or datagram 1 Physical 3 Network H H P Packet 2 Data link H H H P T Frame 1 Physical Header Trailer 7 Application Web server 6 Presentation Router 3 Network H H P Packet 5 Session P Payload 2 Data link H H H P T Frame 4 Transport H P Segment or datagram 1 Physical 3 Network H H P Packet 2 Data link H H H P T Frame 1 Physical Figure 1-20 Follow the red line to see how the OSI layers work when a browser makes a request to a web server The steps listed in Table 1-2 summarize the process illustrated in Figure 1-20. Table 1-2 Steps through the OSI layers during a browser-to-web server transmission Device Task Sending host 1. The browser, involving the application, presentation, and session layers, creates an HTTP message, or payload, on the source computer and passes it down to the transport layer. Sending host 2. The transport layer (TCP, which is part of the OS) encapsulates the payload by adding its own header and passes the segment down to the network layer. Sending host 3. IP at the network layer in the OS receives the segment (depicted as two yellow boxes in the figure), adds its header, and passes the packet down to the data link layer. Sending host 4. The data link layer on the NIC firmware receives the packet (depicted as three yellow boxes in the figure), adds its header and trailer, and passes the frame to the physical layer. Sending host 5. The physical layer on the NIC hardware places bits on the network. Switch 6. The network transmission is received by the switch, which passes the frame up to the data link layer (firmware on the switch), looks at the destination MAC address, and decides where to send the frame. Switch 7. The pass-through frame is sent to the correct port on the switch and on to the next device, which happens to be a router. Router 8. The router has two NICs, one for each of the two networks to which it belongs. The physical layer of the first NIC receives the frame and passes it up to the data link layer (NIC firmware), which removes the frame header and trailer and passes the packet up to IP at the network layer (firmware program or other software) on the router. Router 9. This network layer IP program looks at the destination IP address, determines the next node en route for the packet, and passes the packet back down to the data link layer on the second NIC. The data link layer adds a new frame header and trailer appropriate for this second NIC’s LAN, including the MAC address of the next destination node. It passes the frame to its physical layer (NIC hardware), which sends the bits on their way. Destination host 10. After several iterations of this process at various routers and other networking devices, the frame eventually reaches the destination host NIC. The data link layer NIC firmware receives it, removes the frame header and trailer, and passes the packet up to IP at the network layer, which removes its header and passes the segment up to TCP at the transport layer. Destination host 11. TCP removes its header and passes the payload up to HTTP at the application layer. HTTP presents the message to the web server application. Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove add