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Computer Networking 10 Page Research Paper

Description

The project will consist of a 10-page project paper. The 10 pages include only the text, with everything else extra. You are expected to run a spell checker against the paper. More than 12 pages is not expected. As a matter of fact, it will not help you to include more.

Supporting diagrams or pictures are welcome, but they do not need to be fancy.

The project will be a subset of a network design that still requires you to think about media, hardware, and protocols for either home use or to support a small office.

You will write the paper from the point of view of a network designer, and you will try to solve one of these two problems.

Problem 1

I am sitting in front of my Intel PC, which is running a Windows 7 (or later) operating system, and I am using my Internet Explorer Web browser to access an ISP of your choice. I am doing this at 56 kbs modem speeds, but I want to join the broadband revolution.

You will hook my PC up to some broadband access method. You will describe the overall design; describe specific vendor hardware that makes up the design; describe the transmission media; and describe the protocols within the design (note that this includes TCP/IP and HTTP).

The three approved solutions for this problem are cable TV, DSL, or wireless. For DSL, you should describe the solution from my PC to the DSLAM or the first ATM switch. For cable or wireless, you will have to include an overview of their networks.

Problem 2

I want to set up an Ethernet LAN for my small office of 10 people. The parameters are similar to those of Problem 1, except you will be connecting to a LAN.

For either problem, your design should include the link from my PC or office workstation to the Internet Service Point (ISP) access point within the vendor's network.

You will have to research one of these solutions and then write your paper. For the DSL solution, you should go to one of the DSLAM vendors, such as Lucent; select a DSLAM; and then describe it.

For the cable, wireless, or LAN solutions, you will have to describe how the network components work in general. You will need to include descriptions on the home or office components, as well as an overview of their networks.

Project Grading

The project paper will be graded on the following elements:

· introduction (10%)

· overall design or high-level description (20%)

hardware (10%)

transmission media (10%)

protocol description (10%)

· lessons learned (10%)

· grammar/syntax and length (20%)

· references (10%)

Submitted papers that show evidence of plagiarism will be given a score of zero.
There should be no spelling or grammatical mistakes; the construction should be logical and easy to read. A reference list should be provided at the end of the paper. A minimum of two outside references should be used.

To Cite This Material:

Dean, Tamara. (2013). Comptia network+ n10-005 in depth. [Books24x7 version] Available from http://common.books24x7.com.ezproxy.umuc.edu/toc.aspx?bookid=47482.

Chapter 1: An Introduction to Networking

After reading this chapter and completing the exercises, you will be able to:

· List the advantages of networked computing relative to stand-alone computing

· Distinguish between client/server and peer-to-peer networks

· List elements common to all client/server networks

· Describe several specific uses for a network

· Identify some of the certifications available to networking professionals

· Identify the kinds of skills and specializations that will help you excel as a networking professional

On the Job

I was the chief information officer for a large political research firm that served the president of the United States. I was also teaching at a local community college as an adjunct. Some students just stood out. They were hungry for knowledge. After 15 years of teaching, I could spot the other kind—students who were just there for a grade. Those students seemed to think they didn’t have to work hard in school because they would learn what they needed on the job. Others really wanted to get their money’s worth out of school and learn all they could.

I noticed one student who was always the last one out of class because she was trying to solve some problem or another. The material wasn’t coming easy to her, but I could tell she was curious, and that meant that she was learning things she hadn’t intended to learn. I hired her to work for the political research firm because she never rested until she solved any problem she set out to resolve. Before she even finished college, she was making $45,000 a year at her new job. She was the hardest working member of my staff and I constantly gave her new responsibilities.

After only two years, I left to go to another company, but I didn’t worry about leaving because I knew my former student could handle it. She became the youngest CIO in the history of the firm. Hard work and a lust for learning were the keys to her success.

Michael Bleacher Assistant Dean, School of Technology and School of Business Westwood 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 as large as several thousand computers connected across the world via a combination of cable, phone lines, and cellular links. In addition to connecting personal computers, networks might link mainframe computers, printers, plotters, fax machines, and phone systems. They might communicate through copper wires, fiber-optic cable, or radio waves. This chapter introduces you to the fundamental characteristics of networks.

Why Use Networks?

Using networks offers advantages relative to using a stand-alone computer—that is, a computer that is not connected to other computers and that uses software applications and data stored on its local disks. Most important, networks enable multiple users to share devices (for example, printers) and data (such as spreadsheet files), which are collectively known as the network’s resources. Sharing devices saves money. For example, rather than buying 20 printers for 20 staff members, a company can buy one printer and have those 20 staff members share it over a network. Sharing devices also saves time. For example, it’s faster for coworkers to share data over a network than to copy data to a removable storage device and physically transport the storage device from one computer to another—an outdated file-sharing method commonly referred to as a sneakernet (presumably because people wore sneakers when walking from computer to computer). Before networks, transferring data via floppy disks was the only possible way to share data.

Networks also allow you to manage, or administer, resources on multiple computers from a central location. Imagine you work in the Information Technology (IT) Department of a multinational bank and must verify that each of 5000 employees around the globe uses the same version of a database program. Without a network, you would have to visit every employee’s machine to check and install the proper software. With a network, however, you could provide employees with access to the database program on a single computer using a Web page. Because they allow you to share devices and administer computers centrally, networks increase productivity. It’s not surprising, then, that virtually all organizations depend on their networks to stay competitive.

Types of Networks
Computers can be positioned on a network in different ways relative to each other. They can have different levels of control over shared resources. They can also be made to communicate and share resources according to different schemes. The following sections describe two fundamental network models: peer-to-peer and client/server.

Peer-to-Peer Networks
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The simplest form of a network is a peer-to-peer network. In a peer-to-peer network, every computer can communicate directly with every other computer. By default, no computer on a peer-to-peer network has more authority than another. However, each computer can be configured to share only some of its resources and prevent access to other resources. Traditional peer-to-peer networks typically consist of two or more general-purpose personal computers, with modest processing capabilities. Every computer is capable of sending and receiving information to and from every other computer, as shown in Figure 1-1.

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Figure 1-1: Resource sharing on a simple peer-to-peer network

The following are advantages of using traditional peer-to-peer networks:

· They are simple to configure. For this reason, they may be used in environments in which time or technical expertise is scarce.

· They are often less expensive to set up and maintain than other types of networks. This fact makes them suitable for environments in which saving money is critical.

The following are disadvantages of using traditional peer-to-peer networks:

· They are not very flexible. As a peer-to-peer network grows larger, adding or changing significant elements of the network may be difficult.

· They are also 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 handful of computers because they do not always centralize resources.

For example, if your computer is part of a peer-to-peer network that includes five other computers, and computer users store their spreadsheets and word-processing files on their own hard disks, whenever your colleagues want to edit your files, they must access your machine on the network. If one colleague saves a changed version of one of your spreadsheets on her hard disk, you’ll find it difficult to keep track of which version is the most current. As you can imagine, the more computers you add to a peer-to-peer network, the more difficult it becomes to find and manage resources.

A common way to share resources on a peer-to-peer network is by modifying the file-sharing controls via the computer’s operating system. For example, you could choose to create a directory on your computer’s hard disk called “SharedDocs” and then configure the directory to allow all networked computers to read its files. On a peer-to-peer network, each user is responsible for configuring her computer to allow access to certain resources and prevent access to others. In other words, resource sharing is not controlled by a central computer or authority. Because access depends on many different users, it might not be uniform or secure.

Although traditional peer-to-peer networks are typically small and contained within a home or office, examples of very large peer-to-peer networks have emerged to take advantage of the Internet. These newer types of peer-to-peer networks (commonly called P2P networks) link computers from around the world to share files between each others’ hard disks. Unlike the older style of peer-to-peer network, they require specialized software (besides the computer’s operating system) to allow resource sharing. Examples of these networks include Gnutella, Bitcoin, and the original Napster. In 2001, Napster, which allowed users around the globe to share music files, was forced to cease operation due to charges of copyright infringement from musicians and music producers. Later, the service was redesigned to provide legitimate music file-sharing services. A company called BitTorrent has made a unique high-speed peer-to-peer communications method (also called BitTorrent) the foundation of its business. The company specializes in allowing companies and individuals to share video, audio, software, and games over the Internet. Although BitTorrent’s peer-to-peer technology is legal, its use for distributing illegal or copyrighted materials has generated several lawsuits against the company.

Client/Server Networks
Another way of designing a network is to use a central computer, known as a server, to facilitate communication and resource sharing between other computers on the network, which are known as clients. Clients take the form of personal computers, also known as workstations, or mobile devices, such as smartphones. A network that uses a server to enable clients to share data, data storage space, and devices is known as a client/server network. The term client/server architecture is sometimes used to refer to the design of a network in which clients rely on servers for resource sharing and processing.

In terms of resource sharing and control, you can compare the client/server network with a public library. Just as a librarian manages the use of books and other media by patrons, a server manages the use of shared resources by clients. For example, if a patron does not have the credentials to check out books, the librarian prevents the patron from doing so. Similarly, a server allows only authorized clients to access its resources.

Every computer on a client/server network acts as a client or a server. (It is possible, but uncommon, for some computers to act as both.) Clients on a network can still run applications from and save data to their local hard disk. But by connecting to a server, they also have the option of using shared applications, data, and devices. Clients on a client/server network do not share their resources directly with each other, but rather use the server as an intermediary. Clients and servers communicate through connectivity devices such as switches or routers. These devices are covered in detail in Chapter 6.

Figure 1-2 illustrates how resources are shared on a client/server network.

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Figure 1-2: Resource sharing on a client/server network

To function as a server, a computer must be running an NOS (network operating system).

An NOS is a special type of software designed to do the following:

· Manage data and other resources for a number of clients.

· Ensure that only authorized users access the network.

· Control which type of files a user can open and read.

· Restrict when and from where users can access the network.

· Dictate which rules computers will use to communicate.

· Supply applications to clients.

Examples of popular network operating systems include various forms of UNIX and Linux, Microsoft Windows Server 2008 R2, and Mac OS X Server. By contrast, a stand-alone computer, or a client computer, uses an operating system, such as Windows 7 or a version of Linux, UNIX, or Mac OS, and has authority for managing resources on other computers.

Usually, servers have more memory, processing, and storage capacity than clients. They may even be equipped with special hardware designed to provide network management functions beyond that provided by the network operating system. For example, a server might contain an extra hard disk and specialized software so that if the primary hard disk fails, the secondary hard disk 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, such as:

· User logon accounts and passwords for anyone on a server-based network can be 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.

· Servers are optimized to handle heavy processing loads and dedicated to handling requests from clients, enabling faster response time.

· Because of their efficient processing and larger disk storage, servers can connect more than a handful of computers on a network.

Together, these advantages make client/server networks easier to manage, more secure, and more powerful than peer-to-peer networks. They are also more scalable than peer-to-peer networks. In other words, it is easier to add computers and other devices to a client/server network.

Because client/server networks are by far the most popular type of network, most of the concepts covered in this book and on the Network+ exam pertain to client/server networks. Next, you will learn how networks are classified according to size.

LANs, MANs, and WANs
As its name suggests, a LAN (local area network) is a network of computers and other devices that is confined to a relatively small space, such as one building or even one office. Small LANs first became popular in the early 1980s. At that time, LANs might have consisted of a handful of computers connected in a peer-to-peer fashion. Today’s LANs are typically much larger and more complex client/server networks.

Often, separate LANs are interconnected and rely on several servers running many different applications and managing resources other than data. For example, imagine an office building in which each of a company’s departments runs its own LAN and all the LANs are connected. This network may contain dozens of servers, hundreds of workstations, and several shared storage devices, printers, plotters, fax machines, and even telephone interfaces. Figure 1-3 roughly depicts this type of network (in reality, the network would probably contain many more clients). As you progress through this book, you will learn about the devices on this network and how they communicate. After completing this book, you’ll understand how to integrate clients, servers, and connectivity devices so as to create networks that are reliable, secure, and manageable.

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Figure 1-3: Interconnected LANs

Networks may extend beyond the boundaries of a building. A network that is larger than a LAN and connects clients and servers from multiple buildings—for example, a handful of government offices surrounding a state capitol building—is known as a MAN (metropolitan area network). Because of the distance it covers, a MAN may use different transmission technology and media than a LAN.

A network that connects two or more geographically distinct LANs or MANs is called a WAN (wide area network). Because such networks carry data over longer distances than LANs, WANs may use different transmission methods and media than LANs. Most MANs can also be described as WANs; in fact, network engineers are more likely to refer to all networks that cover a broad geographical range as WANs.

WANs commonly connect separate offices in the same organization, whether they are across town or across the world from each other. For example, imagine you work for a nationwide plumbing supply company that keeps its inventory in warehouses in Topeka, Kansas, and Panama City, Florida. Suppose also that the company’s headquarters is located in New York. When a customer calls and asks whether you have five faucets of a certain type available to ship overnight, you need to check the inventory databases for both the Topeka and Panama City warehouses. Thanks to your WAN, the data are accessible from your New York desktop. Twice a day, the warehouses’ inventory software automatically updates a database located on a central server in New York via WAN links that connect the locations.

WANs are also used to connect LANs that belong to different organizations. For example, all the public universities within a state might combine and share their resources via a WAN. The largest and most varied WAN in the world is the Internet. Figure 1-4 depicts a simple WAN.

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Figure 1-4: A simple WAN

Elements Common to Client/Server Networks

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You have learned that networks, no matter how simple or complex, provide some benefits over stand-alone computers. They also share terminology and common building blocks, some of which you have already encountered. The following list provides a more complete rundown of basic elements common to all client/server networks. You will learn more about these topics throughout this book:

· Client —A computer on the network that requests resources or services from another computer on a network; in some cases, a client could also act as a server. The term client may also refer to the human user of a client workstation or to client software installed on the workstation.

· Server —A computer on the network that manages shared resources; servers usually have more processing power, memory, and hard disk space than clients. They run network operating software that can manage not only data, but also users, groups, security, and applications on the network.

· Workstation —A personal computer (such as a desktop or laptop), which may or may not be connected to a network; most clients are workstation computers.

· NIC (network interface card) —The device (pronounced nick) inside a computer that connects a computer to the network media, thus allowing it to communicate with other computers; many companies (such as Intel, Linksys, and Netgear) manufacture NICs, which come with a variety of specifications that are tailored to the requirements of the workstation and the network. Some connect to the motherboard, which is the main circuit that controls the computer, some are integrated as part of the motherboard, and others connect via an external port. NICs are also known as network adapters. Figure 1-5 depicts a NIC connected to a computer’s motherboard.

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· Figure 1-5: A NIC (network interface card)

Note

Because different PCs and network types require different kinds of NICs, you cannot assume that a NIC that works in one workstation will work in another.

· NOS (network operating system) —The software that runs on a server and enables the server to manage data, users, groups, security, applications, and other networking functions. Examples include various types of UNIX and Linux operating systems, Microsoft Windows Server 2008 R2, and Mac OS X Server.

· Host —A computer that enables resource sharing by other computers on the same network.

· Node —A client, server, or other device that can communicate over a network and that is identified by a unique number, known as its network address.

· Connectivity device —A specialized device that allows multiple networks or multiple parts of one network to connect and exchange data. A small client/server network can operate without connectivity devices. However, medium- and large-sized LANs use them to extend the network and to connect with WANs. WANs use them to connect with the Internet and with other WANs.

· Segment —A part of a network. Usually, a segment is composed of a group of nodes that use the same communications channel for all their traffic.

· Backbone —The part of a network to which segments and significant shared devices (such as routers, switches, and servers) connect. A backbone is sometimes referred to as “a network of networks” because of its role in interconnecting smaller parts of a LAN or WAN. Figure 1-6 shows a LAN with its backbone highlighted in yellow.

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 Figure 1-6: A LAN backbone

 Topology —The physical layout of a computer network. Topologies vary according to the needs of the organization and available hardware and expertise. Networks can be arranged in a ring, bus, or star formation, and the star formation is the most common. Hybrid combinations of these patterns are also possible. Figure 1-7 illustrates these network topologies, which you must understand to design and troubleshoot networks.

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 Figure 1-7: Common network topologies

 Protocol —A standard method or format for communication between networked devices. For example, some protocols ensure that data are transferred in sequence and without error from one node on the network to another. Other protocols ensure that data belonging to a Web page are formatted to appear correctly in a Web browser window. Still others encode passwords and keep data transmissions secure.

 Packet —A distinct unit of data exchanged between nodes on a network. Breaking a large stream of data into many packets allows a network to deliver that data more efficiently and reliably.

 Addressing —The scheme for assigning a unique identifying number to every node on the network. The type of addressing used depends on the network’s protocols and network operating system. Each network device must have a unique address so that data can be transmitted reliably to and from that device.

 Transmission media —The means through which data are transmitted and received. Transmission media may be physical, such as wire or cable, or atmospheric (wireless), such as radio waves. Figure 1-8 shows several examples of transmission media. Chapter 3, which explains physical transmission media in detail, offers additional images of network cabling.

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· Figure 1-8: Examples of network transmission media

Now that you are familiar with basic network terminology, you are ready to appreciate the many uses of computer networks.

How Networks Are Used
The functions provided by a network are usually referred to as network services. Any network manager will tell you that the network service with the highest visibility is e-mail. If your company’s e-mail system fails, users will notice within minutes—and they will not be shy about informing you of the failure. Although e-mail may be the most visible network service, other services can be just as vital. Printer sharing, file sharing, Internet access and Web site delivery, remote access capabilities, the provision of voice (telephone) and video services, and network management are all critical business functions provided through networks. In large organizations, separate servers may be dedicated to performing each of these functions. In offices with only a few users and little network traffic, one server may perform all functions.

File and Print Services
The term file services refers to a server’s ability to share data files, applications (such as word-processing or spreadsheet programs), and disk storage space. A server that provides file services is called a file server. File services accounted for the first use of networks and remain the foundation of networking today, for a number of reasons. As mentioned earlier, it is easier and faster to store shared data at a central location than to copy files to disks and then pass the disks around. Data stored at a central location is typically more secure because a network administrator can take charge of backing up this data, rather than relying on individual users to make their own copies. In addition, using a file server to run applications for multiple users requires the purchase of fewer copies of the application and less maintenance work for the network administrator.

Using print services to share printers across a network also saves time and money. A high-capacity printer can cost thousands of dollars, but can handle the printing tasks of an entire department, thereby eliminating the need to buy a desktop printer for each worker. With one printer, less time is spent on maintenance and management. If a shared printer fails, the network administrator can diagnose the problem from a workstation anywhere on the network using the network operating system’s printer control functions. Often, the administrator can solve the problem without even visiting the printer.

Access Services
A network’s access services allow remote users to connect to the network. (The term remote user refers to a person working on a computer on a different network or in a different geographical location from the LAN’s server.) Less frequently, access services allow network users to connect to machines outside the network. Most network operating systems include built-in access services that enable users to dial in to a remote access server, log on to the network, and take advantage of the network just as if they were logged on to a workstation on the office LAN. A remote access server may also be known as simply an access server.

Organizations might use access services to provide LAN connectivity for workers at home, workers on the road, and workers at small satellite offices where dedicated WAN connections are not cost effective. In addition, access services can allow staff from other organizations (such as a software or hardware vendor) to help diagnose a network problem. For example, suppose you work for a clothing manufacturer that uses embroidery software to control the machines that sew insignias on shirts and hats. You are an expert on networking, but less adept with the automated embroidery software. When the software causes problems, you turn to the software vendor for help. But suppose the vendor’s technician can’t solve the problem except by logging on to your network. In that case, it is much more efficient and less expensive to allow the technician to dial in to your network through a remote access server than to fly the technician to your office.

It is important to remember that remote access servers—no matter which platform (hardware or operating system software) they run on—allow external users to use network resources and devices just as if they were logged on to a workstation in the office. From a remote location, users can print files to shared printers, log on to hosts, retrieve mail from an internal messaging system, or run queries on internal databases. Because they can be accessed by the world outside the local network, remote access servers necessitate strict security measures.

Communications Services
Today’s networks can help users communicate in many ways: e-mail, telephone, video, fax, cell phone, smartphone (for example, an iPhone), and personal digital assistant (for example, a BlackBerry). Using the same network to deliver multiple types of communications services is known as convergence. A similar term, unified communications, refers to the centralized management of multiple network-based communications. For example, your company might use one software program to manage intraoffice phone calls, long-distance phone calls, cell phone calls, voice mail, faxes, and text messaging for all the users on your network. Chapter 12 describes how networks deliver these services.

The oldest network communications services are mail services, which coordinate the storage and transfer of e-mail between users on a network. The computer responsible for mail services is called a mail server. Mail servers are usually connected to the Internet, but when clients only need to exchange e-mail within their organization, their mail server may be isolated on their LAN.

In addition to simply sending, receiving, and storing mail, mail servers can do the following:

· Intercept or filter unsolicited e-mail, known as spam.

· Find objectionable content in e-mails and do something about that content, such as flagging it to make the recipient aware of it.

· Route messages according to particular rules. For example, if a technical support representative has not opened a customer’s message within 15 minutes of delivery, a mail server could automatically forward the message to a supervisor.

· Provide a Web-based client for checking e-mail.

· Notify administrators or users if certain events occur, such as a user’s mailbox exceeding its maximum amount of space on a server.

· Schedule e-mail transmission, retrieval, storage, and maintenance functions.

· Communicate with mail servers on other networks so that mail can be exchanged between users who do not connect to the same LAN.

To supply these services, a mail server runs specialized mail server software, examples of which include Sendmail and Microsoft Exchange Server. Because of their critical nature and heavy use, maintaining a mail server in any sizable organization requires a significant commitment of technical support and administration resources.

Internet Services
You have probably connected to the Internet without knowing or caring about all of the services running behind the scenes. But in fact, many servers are working together to bring Web pages to your desktop. For example, a Web server is a computer installed with the appropriate software to supply Web pages to many different clients upon demand. The most popular Web server software is Apache. It’s used to deliver more than 60 percent of Web pages on the Internet.

Supplying Web pages is only one type of Internet service. Other Internet services include file transfer capabilities, Internet addressing schemes, security filters, and a means for directly logging on to other computers on the Internet.

Management Services
When networks were small and simple, a single network administrator could manage the entire network. For instance, suppose a user called to report a problem logging on to the network and that the administrator diagnosed the problem as an addressing conflict (that is, two workstations having the same network address). In a very small network, the conflicting workstations might be located right around the corner from each other, and one address could be changed quickly. In another example, if a manager needed to report the number of copies of Adobe Photoshop in use in a certain department, the network administrator could probably get the desired information by just walking through the department and checking the various workstations.

As networks grow larger and more complex, however, they become more difficult to manage. Using network management services can help you keep track of a large network. Network management services centrally administer management tasks on the network, such as ensuring that no more than 20 workstations are using Adobe Photoshop at one time in an organization that purchased a 20-user license for the software. Some organizations dedicate a number of servers to network management functions, with each server performing only one or two unique services.

Numerous services fall under the category of network management. Some of the most important ones include the following:

· Traffic monitoring and control —Determining how much traffic, or data transmission activity, is taking place on a network and notifying administrators when the network becomes overloaded. In general, the larger the network, the more critical it is to monitor traffic.

· Load balancing —Distributing data transfer activity evenly so that no single device becomes overwhelmed. Load balancing is especially important for networks in which it’s difficult to predict the number of requests that will be issued to a server, as is the case with Web servers.

· Hardware diagnosis and failure alert —Determining when a network component fails and automatically notifying the network administrator through an e-mail or text message.

· Asset management —Collecting and storing data on the number and types of software and hardware assets in an organization’s network. With asset management software, a server can electronically examine each client’s software and hardware and automatically save the data in a database. Other types of assets might be identified and tracked using RFID (Radio Frequency Identification) tags, which emit a wireless signal at all times. Wireless detection devices connected to a network can track the locations of RFID-tagged devices. For example, a hospital might use RFID tags to keep track of the wheelchairs, beds, and IV pumps that circulate throughout its campus. Before asset management services, inventory data had to be gathered manually and typed into spreadsheets.

· License tracking —Determining how many copies of a single application are currently in use on the network and ensuring that number does not exceed the number of licenses purchased. This information is important for legal reasons, as software companies are vigilant about illegally copying software or using more than the authorized number of copies.

· Security auditing —Evaluating what security measures are currently in force and notifying the network administrator if a security breach occurs.

· Software distribution —Automatically transferring a file or installing an application from the server to a client on the network. The installation process can be started from either the server or the client. Several options are available when distributing software, such as warning users about updates, writing changes to a workstation’s system files, and restarting the workstation after the update.

· Address management —Centrally managing a finite number of network addresses for an entire network. Usually this task can be accomplished without manually modifying the client workstation configurations.

· Backup and restoration of data —Backing up critical data files to a secure storage area and then restoring data if the original files are lost or deleted. Often backups are performed according to a formulaic schedule. Backup and data restoration services provide centralized management of data backup on multiple servers and on-demand restoration of files and directories.

Network management services will be covered in depth later in the book. For now, it is enough to be aware of the variety of services and the importance of this growing area of networking.

Becoming a Networking Professional
If you search online employment services, you’ll probably find hundreds of postings for computer professionals. Of course, the level of expertise required for each of these jobs differs. Some companies simply need “warm bodies” to ensure that a higher-level engineer is notified if a critical network segment fails; other companies are looking for people to plan their global information technology strategies. Needless to say, the more extensive your skills, the better your chances for landing a lucrative and interesting job in networking. To prepare yourself to enter this job market, master a number of general networking technologies. Only then should you pick a few areas that interest you and study those specialties. Hone your communication and teamwork skills, and stay abreast of emerging technologies. Consider the tremendous advantages of attaining professional certification and getting to know others in your field. The following sections offer suggestions on how to approach a career in networking.

Mastering the Technical Challenges
Although computer networking is a varied field, some general technical skills will serve you well no matter which specialty you choose. Because you are already interested in computers, you probably enjoy an aptitude for logical and analytical thinking. You probably also want to acquire these skills:

· Installing, configuring, and troubleshooting network server software and hardware

· Installing, configuring, and troubleshooting network client software and hardware

· Understanding the characteristics of different transmission media

· Understanding network design

· Understanding network protocols

· Understanding how users interact with the network

· Constructing a network with clients, servers, media, and connectivity devices

Because you can expand your networking knowledge in almost any direction, you should pay attention to the general skills that interest you most, then pick one or two of those areas and concentrate on them. The following specialties are currently in high demand:

· Network security

· Convergence (the delivery of voice, video, and data over a single network)

· In-depth knowledge about one or more NOSs: UNIX, Linux, Mac OS X Server, or Microsoft Windows Server 2008 R2

· Network management

· Wireless network design

· Configuration and optimization of routers and switches

· Centralized data storage and management for large-scale environments

Determine which method of learning works best for you. A small classroom with an experienced instructor and a hands-on projects lab is an excellent learning environment because there you can ask questions and learn by doing. There is no substitute for hands-on experience when it comes to improving your networking hardware and software skills. If you don’t already work in an IT department, try to find a position that puts you in that environment, even if it isn’t your dream job. Volunteer a few hours a week if necessary. After you are surrounded with other information technology professionals and encounter real-life situations, you will have the opportunity to expand your skills by practicing and asking questions of more experienced staff. On the Web, you can find a number of searchable online job boards and recruiter sites. The placement office at your local college or university can also connect you with job opportunities.

Developing Your Soft Skills
Knowing how to configure a router or install UNIX will serve you well, but advanced soft skills will help you stand out. The term soft skills refers to those skills that are not easily measurable, such as customer relations, oral and written communications, dependability, teamwork, and leadership abilities. Some soft skills might appear to be advantages in any profession, but they are especially important when you must work in teams, in challenging technical circumstances, and under tight deadlines—requirements that apply to most networking projects. For this reason, soft skills merit closer examination:

· Customer relations —Perhaps one of the most important soft skills, customer relations involve an ability to listen to customers’ frustrations and desires and then empathize, respond, and guide customers to their goals without acting arrogant. Bear in mind that some of your customers will not appreciate or enjoy technology as much as you do, and they will value your patience as you help them. The better your customer relations, the more respected and popular you will be as a network professional.

· Oral and written communications —You may understand the most complicated technical details about a network, but if you cannot communicate them to colleagues and clients, the significance of your knowledge is diminished. Imagine that you are a networking consultant who is competing with several other firms to overhaul a metropolitan hospital’s network, a project that could generate millions of dollars for your company. You may have designed the best solution and have it clearly mapped out in your head, but your plan is useless if you can’t describe it clearly. The hospital’s planning committee will accept whichever proposal makes the most sense to them—that is, the proposal whose suggestions and justifications are plainly communicated.

· Dependability —This characteristic will help you in any career. However, in the field of networking, where breakdowns or glitches can occur at any time of day or night and only a limited number of individuals have the expertise to fix them, being dependable is critical. Your career will benefit when you are the one who is available to address a problem, even if you don’t always know the answer immediately.

· Teamwork —Individual computer professionals often have strong preferences for a certain type of hardware or software. Some technical people like to think that they have all of the answers. For these and other reasons, teamwork in IT departments is sometimes lacking. To be the best networking professional in your department, you must be open to new ideas, encourage cooperation among your colleagues, and allow others to help you and make suggestions.

· Leadership abilities —As a networking professional, you will sometimes need to make difficult or unpopular decisions under pressure. You may need to persuade opinionated colleagues to try a new product, tell a group of angry users that what they want is not possible, or manage a project with nearly impossible budgetary and time restrictions. In all of these situations, you will benefit from having strong leadership skills.

After your career in networking begins, you will discover which soft skills you already possess and which ones you need to cultivate. The important thing is that you realize the importance of these attributes and are willing to devote the time necessary to develop them.

Pursuing Certification
Certification is the process of mastering material pertaining to a particular hardware system, operating system, programming language, or software application, then proving your mastery by passing a series of exams. Certification programs are developed and administered either by a manufacturer or a professional organization such as CompTIA (Computing Technology Industry Association). You can pursue a number of different certifications, depending on your specialty interest. For example, if you want to become a PC technician, you should attain A+ certification. If you want to specialize in Microsoft product support and development, pursue MCITP (Microsoft Certified IT Professional) certification. To specialize in the configuration and management of Cisco Systems’ switches and routers, work toward Cisco’s CCNA (Cisco Certified Network Associate) or go for their most difficult and prestigious distinction, CCIE (Cisco Certified Internetwork Expert) certification, which requires candidates to pass lab exams. To prove a mastery of many aspects of networking, you can choose to become Network+ certified. Network+ (Net+) is a professional certification established by CompTIA that verifies broad, vendor-independent networking technology skills, such as an understanding of protocols, topologies, networking hardware, and network troubleshooting. Network+ may also be a stepping stone to more advanced certifications. The material in this book addresses the knowledge objectives you must understand to qualify for Network+ certification.

Certification is a popular career development tool for job seekers and a measure of an employee’s qualifications for employers. Following are a list of benefits to becoming certified:

· Better salary —Professionals with certification can usually ask for higher salaries than those who aren’t certified. Employers will also want to retain certified employees, especially if they helped pay for their training, and will offer incentives to keep certified professionals at the company.

· Greater opportunities —Certification may qualify you for additional degrees or more advanced technical positions.

· Professional respect —After you have proven your skills with a product or system, your colleagues and clients will gain great respect for your ability to solve problems with that system or product. They will therefore feel confident asking you for help.

· Access to better support —Many manufacturers reward certified professionals with less-expensive, more detailed, and more direct access to their technical support.

Finding a Job in Networking
With the proper credentials and demonstrated technical knowledge, you will qualify for a multitude of positions in networking. For this reason, you can and must be selective when searching for a job. Following are some ways to research your possibilities:

· Search the Web —Because your job will deal directly with technology, it makes sense to use technology to find it. Companies in the computer industry recruit intensively on the Web, either through searchable job databases or through links on their company Web sites. Most job database Web sites do not charge for their services, but may require you to register with them. One popular general Web job database is Monster at www.monster.com . IT-specific job sites include Dice at www.dice.com , Slashdot Jobs at jobs.slashdot.org , and computerjobs.com . A simple Web search could yield dozens more.

· Check your local newspaper’s Web site —Although many employers list job openings through national online services, some with specific, local opportunities might advertise only in a local or regional newspaper’s online classifieds. It’s worth checking the Web site of your newspaper for these types of listings.

· Visit a career center —Regardless of whether you are a registered university or college student, you can use career center services to find a list of job openings in your area. Companies that are hiring pay much attention to the collegiate career centers because of the number of job seekers served by these centers. Visit the college or university campus nearest you and search through its career center listings.

· Network —Find like-minded professionals with whom you can discuss job possibilities. You may meet these individuals through training classes, conferences, professional organizations, or career fairs. Let them know that you are looking for a job, and specify exactly what kind of job you want. If they can’t suggest any leads for you, ask these people if they have other colleagues who might.

· Attend career fairs —Most metropolitan areas host career fairs for job seekers in the information technology field, and some large companies host their own job fairs. Even if you aren’t sure you want to work for any of the companies represented at a job fair, attend the job fair to research the market. You can find out which skills are in high demand in your area and which types of companies are hiring the most networking professionals. You can also meet other people in your field who may offer valuable advice based on their employment experience.

· Enlist a recruiter —Many recruiting agencies deal strictly with clients in the technical fields. By signing up with such a recruiting agency, you may have access to job opportunities that you didn’t know existed. You might also take advantage of a temporary assignment, to see if the fit between you and an employer is mutually beneficial, before accepting a permanent job with that employer.

Joining Professional Associations
Joining an organization can connect you with people who have similar interests, provide new opportunities for learning, allow you to access specialized information, and give you more tangible assets such as free goods. Specifically, a networking professional organization might offer its own publications, technical workshops and conferences, free software, prerelease software, and access to expensive hardware labs.

You can choose from several prominent professional organizations in the field of networking. Because the field has grown so quickly, with so many areas in which to specialize, no single professional organization stands out as the most advantageous or highly respected. You will have to decide whether an organization is appropriate for you. Among other things, you will want to consider the organization’s total membership, membership benefits, membership dues, technical emphasis, and whether it hosts a local chapter. Many organizations host student chapters on university campuses. You may also want to find a professional association that caters to your demographic group (such as Women in Technology International, if you are female). Table 1-1 lists some professional organizations and their Web sites.

Table 1-1: Some networking organizations Open table as spreadsheet

Professional organization

Web site

Association for Computing Machinery (ACM)

www.acm.org

Association of Information Technology Professionals

www.aitp.org

IEEE Computer Society

www.computer.org

Network Professional Association

www.npanet.org

Women in Technology International (WITI)

www.witi.org

© Cengage Learning 2013

Chapter Summary
· A network is a group of computers and other devices (such as printers) that are connected by some type of transmission media, such as copper or fiber-optic cable or radio waves, in the case of wireless transmission.

· All networks offer advantages relative to using a stand-alone computer. Networks enable multiple users to share devices and data. Sharing resources saves time and money. Networks also allow you to manage, or administer, resources on multiple computers from a central location.

· In a peer-to-peer network, every computer can communicate directly with every other computer. By default, no computer on a peer-to-peer network has more authority than another. However, each computer can be configured to share only some of its resources and keep other resources inaccessible.

· Traditional peer-to-peer networks are usually simple and inexpensive to set up. However, they are not necessarily flexible or secure.

· Client/server networks rely on a centrally administered server (or servers) to manage shared resources for multiple clients. In this scheme, the server has greater authority than the clients, which may be desktop or laptop workstations or mobile devices, such as cell phones.

· Client/server networks are more complex and expensive to install than peer-to-peer networks. However, they are more easily managed, more scalable, and typically more secure. They are by far the most popular type of network in use today.

· Servers typically possess more processing power, hard disk space, and memory than client computers. To manage access to and use of shared resources, among other centralized functions, a server requires a network operating system.

· A LAN (local area network) is a network of computers and other devices that is confined to a relatively small space, such as one building or even one office.

· LANs can be interconnected to form WANs (wide area networks), which traverse longer distances and may use different transmission methods and media than LANs. The Internet is the largest example of a WAN.

· Client/server networks share some common elements, including clients, servers, workstations, transmission media, connectivity devices, protocols, addressing, topology, NICs, packets, network operating systems, hosts, backbones, segments, and nodes.

· Networks provide a wide range of services, including printing, file sharing, Internet access, remote access, communicating in multiple forms, and network management.

· File and print services provide the foundation for networking. They enable multiple users to share data, applications, storage areas, and printers.

· Networks use access services to allow remote users to connect to the network or network users to connect to machines outside the network.

· Communications services provided by networks include e-mail, telephone, video, fax, messaging, and voice mail.

· Mail services (running on mail servers) allow users on a network to exchange and store e-mail. Most mail packages also provide filtering, routing, scheduling, notification, and connectivity with other mail systems.

· Internet services such as Web servers and browsers, file transfer capabilities, addressing schemes, and security filters enable organizations to connect to and use the global Internet.

· Network management services centrally administer and simplify complicated management tasks on the network, such as asset management, security auditing, hardware problem diagnosis, backup and restore services, license tracking, load balancing, and data traffic control.

· To prepare yourself for a networking career, master a number of broad networking skills, such as installing and configuring client and server hardware and software. Then pick a few areas that interest you, such as network security or voice/data integration, and study those specialties.

· Certification is the process of mastering material pertaining to a particular hardware system, operating system, programming language, or other software program, then proving your mastery by passing a series of exams. The benefits of certification can include a better salary, more job opportunities, greater professional respect, and better access to technical support.

· To excel in the field of networking, hone your soft skills, such as customer relations, oral and written communications, dependability, teamwork, and leadership abilities.

· Joining an association for networking professionals can connect you with like-minded people, give you access to workshops and technical publications, allow you to receive discounted or free software, and perhaps even help you find a job in the field.

Chapter 2: Networking Standards and the OSI Model
After reading this chapter and completing the exercises, you will be able to:

· Identify organizations that set standards for networking

· Describe the purpose of the OSI model and each of its layers

· Explain specific functions belonging to each OSI model layer

· Understand how two network nodes communicate through the OSI model

· Discuss the structure and purpose of data packets and frames

· Describe the two types of addressing covered by the OSI model

On the Job

While I was working as a junior project manager in the Technology Solutions Department for a large corporation, I was assigned to work on a network infrastructure project. At the time, I had no training as a network engineer, and was instead responsible for small- to medium-sized technology projects as they related to a business unit that spanned five states. For this new project, our goal was to change the network’s topology in a way that would allow the network to grow over time for the least amount of money, and to keep the network up-to-date with the latest trends within the industry.

As with most projects, a budget was set at the beginning. This budget allowed us to hire a professional vendor to complete the wiring and cabling installations. The network engineers who worked for the vendor were experts on everything related to wiring and cabling. However, before they could get very far, our budget was aggressively reduced. Suddenly, we could no longer afford the cabling experts. Instead, senior managers decided that work would be completed by our company’s own junior IT technicians, people who were better suited to printer paper jam resolution than recabling an entire network. They knew nothing about hierarchical cable structure, maximum cable distances, or endpoint terminations.

This ignorance of basic networking standards had dire consequences on our project’s budget and timeline. But the problem wasn’t just that the IT people doing the work lacked the proper knowledge. As the project manager, with no systematic knowledge of networking standards, I was also hampered in my ability to keep things on track.

Part of a successful project manager’s job is recognizing the need for subject matter experts, or at least being able to understand where to find key pieces of information related to the project and then interpreting that information as it relates to the project. In my case, a simple understanding of a set of telecommunications standards, or TIA/EIA-568, would have been indispensable in completing the network topology change project.

Our in-house team began the project on a vacant floor that was to become new employee office space. We unknowingly exceeded cable runs, terminated wall outlet connection points incorrectly, and generally did a poor installation job. Only after new client computers were installed and exhibited a variety of connection issues did we realize our installation was most likely the culprit. We soon understood that our lack of prior planning and our ignorance of industry standards were to blame. Through painful trial and error, we gained an in-depth knowledge of telecommunications structured cabling and the tools needed to implement a network topology change, but with the cost of this knowledge was a lot of time on a ladder removing ceiling tiles and working late into the night to ensure clients were able to effectively run their applications at the start of the next workday.

Tom Johnson Segment Account Manager, Defense Industry

When trying to grasp a new theoretical concept, it often helps to form a picture of that concept in your mind. In the field of chemistry, for example, even though you can’t see a water molecule, you can represent it with a simple drawing of two hydrogen atoms and one oxygen atom. Similarly, in the field of networking, even though you can’t see the communication that occurs between two nodes on a network, you can use a model to depict how the communication takes place. The model commonly used to describe network communications is called the OSI (Open Systems Interconnection) model.

In this chapter, you will learn about the standards organizations that have helped create the various conventions (such as the OSI model) used in networking. Next, you’ll be introduced to the seven layers of the OSI model and learn how they interact. You will then take a closer look at what goes on in each layer. Finally, you will learn to apply those details to a practical networking environment. Granted, learning the OSI model is not the most exciting part of becoming a networking expert. Thoroughly understanding it, however, is essential to proficient network design and troubleshooting.

Networking Standards Organizations
Standards are documented agreements containing technical specifications or other precise criteria that stipulate how a particular product or service should be designed or performed. Many different industries use standards to ensure that products, processes, and services suit their purposes. For example, the construction industry follows standards to ensure a building’s safety and accessibility, such as those defining the width and slope of wheelchair ramps. The airline industry adheres to standards that specify the precise contents of jet fuel.

Because of the wide variety of hardware and software in use today, standards are especially important in the world of networking. Without standards, it would be very difficult to design a network because you could not be certain that software or hardware from different manufacturers would work together. For example, if one manufacturer designed a network cable with a 1-centimeter-wide plug and another company manufactured a wall plate with a 0.8-centimeter-wide opening, you would not be able to insert the plug into the wall plate.

When purchasing networking equipment, therefore, you want to verify that equipment meets the standards your network requires. However, bear in mind that standards define the minimum acceptable performance of a product or service—not the ideal. So, for example, you might purchase two different network cables that comply with the minimum standard for transmitting at a certain speed, but one cable might exceed that standard, allowing for better network performance. In the case of network cables, exceeding minimum standards often follows from the use of quality materials and careful production techniques.

Because the computer industry grew so quickly out of several technical disciplines, many different organizations evolved to oversee its standards. In some cases, a few organizations are responsible for a single aspect of networking. For example, both the American National Standards Institute (ANSI) and IEEE are involved in setting standards for wireless networks. Whereas ANSI prescribes the kind of NIC (network interface card) that the consumer needs to accept a wireless connection, IEEE prescribes, among other things, how the network will ensure that different parts of a communication sent through the atmosphere arrive at their destination in the correct sequence.

A complete list of the standards that regulate computers and networking would fill an encyclopedia. Although you don’t need to know the fine points of every standard, you should be familiar with the groups that set networking standards and the critical aspects of standards required by your network.

ANSI
ANSI (American National Standards Institute) is an organization composed of more than a thousand representatives from industry and government who together determine standards for the electronics industry and other fields, such as chemical and nuclear engineering, health and safety, and construction. ANSI also represents the United States in setting international standards. This organization does not dictate that manufacturers comply with its standards, but requests voluntarily compliance. Of course, manufacturers and developers benefit from compliance, because compliance assures potential customers that the systems are reliable and can be integrated with an existing infrastructure. New electronic equipment and methods must undergo rigorous testing to prove they are worthy of ANSI’s approval.

You can purchase ANSI standards documents online from ANSI’s Web site ( www.ansi.org ) or find them at a university or public library. You need not read complete ANSI standards to be a competent networking professional, but you should understand the breadth and significance of ANSI’s influence.

EIA and TIA
Two related standards organizations are EIA and TIA. EIA (Electronic Industries Alliance) is a trade organization composed of representatives from electronics manufacturing firms across the United States. EIA not only sets standards for its members, but also helps write ANSI standards and lobbies for legislation favorable to the growth of the computer and electronics industries.

In 1988, one of the EIA’s subgroups merged with the former United States Telecommunications Suppliers Association (USTSA) to form TIA (Telecommunications Industry Association). TIA focuses on standards for information technology, wireless, satellite, fiber optics, and telephone equipment. Both TIA and EIA set standards, lobby governments and industry, and sponsor conferences, exhibitions, and forums in their areas of interest.

Probably the best known standards to come from the TIA/EIA alliance are its guidelines for how network cable should be installed in commercial buildings, known as the “TIA/EIA 568-B Series.” You’ll learn about following these guidelines while terminating cables in Chapter 3. You can find out more about TIA from its Web site, www.tiaonline.org , and EIA from its Web site, www.eia.org .

IEEE
The IEEE (Institute of Electrical and Electronics Engineers), or “I-triple-E,” is an international society composed of engineering professionals. Its goals are to promote development and education in the electrical engineering and computer science fields. To this end, IEEE hosts numerous symposia, conferences, and local chapter meetings and publishes papers designed to educate members on technological advances. It also maintains a standards board that establishes its own standards for the electronics and computer industries and contributes to the work of other standards-setting bodies, such as ANSI.

IEEE technical papers and standards are highly respected in the networking profession. Among other places, you will find references to IEEE standards in the manuals that accompany NICs. You can purchase IEEE documents online from IEEE’s Web site ( www.ieee.org ) or find them in a university or public library.

ISO
ISO (International Organization for Standardization), headquartered in Geneva, Switzerland, is a collection of standards organizations representing 162 countries. ISO’s goal is to establish international technological standards to facilitate global exchange of information and barrier-free trade. Given the organization’s full name, you might expect it to be called IOS, but ISO is not meant to be an acronym. In fact, iso is the Greek word for equal. Using this term conveys the organization’s dedication to standards.

ISO’s authority is not limited to the information-processing and communications industries. It also applies to the fields of textiles, packaging, distribution of goods, energy production and utilization, shipbuilding, and banking and financial services. The universal agreements on screw threads, bank cards, and even the names for currencies are all products of ISO’s work. In fact, fewer than 3000 of ISO’s more than 18,500 standards apply to computer-related products and functions. You can find out more about ISO at its Web site: www.iso.org .

ITU
The ITU (International Telecommunication Union) is a specialized United Nations agency that regulates international telecommunications, including radio and TV frequencies, satellite and telephony specifications, networking infrastructure, and tariffs applied to global communications. It also provides developing countries with technical expertise and equipment to advance those nations’ technological bases.

The ITU was founded in Paris in 1865. It became part of the United Nations in 1947 and relocated to Geneva, Switzerland. Its standards arm contains members from 193 countries and publishes detailed policy and standards documents that can be found on its Web site: www.itu.int . Typically, ITU documents pertain more to global telecommunications issues than to industry technical specifications. However, the ITU is deeply involved with the implementation of worldwide Internet services. As in other areas, the ITU cooperates with several different standards organizations, such as ISOC (discussed next), to develop these standards.

ISOC
ISOC (Internet Society), founded in 1992, is a professional membership society that helps to establish technical standards for the Internet. Some current ISOC concerns include the rapid growth of the Internet and keeping it accessible, information security, and the need for stable addressing services and open standards across the Internet. ISOC’s membership consists of more than 44,000 Internet professionals from over 80 chapters around the world.

ISOC oversees groups with specific missions, such as the IAB (Internet Architecture Board). IAB is a technical advisory group of researchers and technical professionals interested in overseeing the Internet’s design and management. As part of its charter, IAB is responsible for Internet growth and management strategy, resolution of technical disputes, and standards oversight.

Another ISOC group is the IETF (Internet Engineering Task Force), the organization that sets standards for how systems communicate over the Internet—in particular, how protocols operate and interact. Anyone can submit a proposed standard for IETF approval. The standard then undergoes elaborate review, testing, and approval processes. On an international level, IETF works with the ITU to help give technical standards approved in the United States international acceptance. You can learn more about ISOC and its member organizations, IAB and IETF, at their Web site: www.isoc.org .

IANA and ICANN
You have learned that every computer on a network must have a unique address. On the Internet, this is especially important because millions of different computers must be available to transmit and receive data at any time. Addresses used to identify computers on the Internet and other TCP/IP-based networks are known as IP (Internet Protocol) addresses. To ensure that every Internet-connected device has a unique IP address, organizations across the globe rely on centralized authorities.

In early Internet history, a nonprofit group called the IANA (Internet Assigned Numbers Authority) kept records of available and reserved IP addresses and determined how addresses were doled out. Starting in 1997, IANA coordinated its efforts with three RIRs (Regional Internet Registries): ARIN (American Registry for Internet Numbers), APNIC (Asia Pacific Network Information Centre), and RIPE (Reseaux IP Europeens). An RIR is a not-for-profit agency that manages the distribution of IP addresses to private and public entities. In the late 1990s, the United States Department of Commerce (DOC), which funded IANA, decided to overhaul IP addressing and domain name management. The DOC recommended the formation of ICANN (Internet Corporation for Assigned Names and Numbers), a private, nonprofit corporation. ICANN is now ultimately responsible for IP addressing and domain name management. Technically speaking, however, IANA continues to perform the system administration.

Individuals and businesses do not typically obtain IP addresses directly from an RIR or IANA. Instead, they lease a group of addresses from their ISP (Internet service provider), a business that provides organizations and individuals with access to the Internet and often, other services, such as e-mail and Web hosting. An ISP, in turn, arranges with its RIR for the right to use certain IP addresses on its network. The RIR obtains its right to dole out those addresses from ICANN. In addition, the RIR coordinates with IANA to ensure that the addresses are associated with devices connected to the ISP’s network. You can learn more about IANA and ICANN at their Web sites, www.iana.org and www.icann.org , respectively.

The OSI Model
C:\Users\Jeremiah\Desktop\f0034-01.jpg

In the early 1980s, ISO began work on a universal set of specifications that would enable computer platforms across the world to communicate openly. The result was a helpful model for understanding and developing computer-to-computer communications over a network. This model, called the OSI (Open Systems Interconnection) model, divides network communications into seven layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application. At each layer, protocols perform services unique to that layer. While performing those services, the protocols also interact with protocols in the layers directly above and below. In addition, at the top of the OSI model, Application layer protocols interact with the software you use (such as an e-mail or spreadsheet program). At the bottom, Physical layer services act on the networking cables and connectors to issue and receive signals.

You have already learned that protocols are the rules by which computers communicate. A protocol is simply a set of instructions written by a programmer to perform a function or group of functions. Some protocols are included with a computer’s operating system. Others are files installed with software programs. Chapter 4 covers protocols in depth; however, some protocols are briefly introduced in the following sections to better explain what happens at each layer of the OSI model.

The OSI model is a theoretical representation of what happens between two nodes communicating on a network. It does not prescribe the type of hardware or software that should support each layer. Nor does it describe how software programs interact with other software programs or how software programs interact with humans. Every process that occurs during network communications can be associated with a layer of the OSI model, so you should be familiar with the names of the layers and understand the key services and protocols that belong to each.

Tip

Networking professionals often devise a mnemonic way of remembering the seven layers of the OSI model. One strategy is to make a sentence using words that begin with the same first letter of each layer, starting with either the lowest (Physical) or the highest (Application) layer. For example, you might choose to remember the phrase “Programmers Dare Not Throw Salty Pretzels Away.” Quirky phrases are often easiest to remember.

The path that data takes from one computer to another through the OSI model is illustrated in Figure 2-1. First, a user or device initiates a data exchange through the Application layer. The Application layer separates data into PDUs (protocol data units), or discrete amounts of data. From there, Application layer PDUs progress down through OSI model layers 6, 5, 4, 3, 2, and 1 before being issued to the network medium—for example, the wire. The data traverses the network until it reaches the second computer’s Physical layer. Then at the receiving computer the data progresses up the OSI model until it reaches the second computer’s Application layer. This transfer of information happens in milliseconds.

C:\Users\Jeremiah\Desktop\f0036-01.jpg

Figure 2-1: Flow of data through the OSI model

Logically, however, each layer communicates with the same layer from one computer to another. In other words, the Application layer protocols on one computer exchange information with the Application layer protocols of the second computer. Protocols from other layers do not attempt to interpret Application layer data. In the following sections, the OSI model layers are discussed from highest to lowest, beginning with the Application layer, where the flow of information is initiated.

Bear in mind that the OSI model is a generalized and sometimes imperfect representation of network communication. In some cases, network functions can be associated with more than one layer of the model, and in other cases, network operations do not require services from every layer.

Application Layer
The top, or seventh, layer of the OSI model is the Application layer. Contrary to what its name implies, the Application layer does not include software programs, such as Microsoft Word or Firefox. Instead, the Application layer facilitates communication between such programs and lower-layer network services. Services at this layer enable the network to interpret a program’s request and the program to interpret data sent from the network. Through Application layer protocols, programs negotiate their formatting, procedural, security, synchronization, and other requirements with the network. Note that not all these requirements are fulfilled by Application layer protocols. They are merely agreed upon at this stage.

C:\Users\Jeremiah\Desktop\f0036-02.jpg

For example, when you choose to open a Web page in Firefox, an Application layer protocol called HTTP (Hypertext Transfer Protocol) formats and sends your request from your client’s browser (a software application) to the server. It also formats and sends the Web server’s response back to your client’s browser. Figure 2-2 illustrates how the Application layer services operate in this example.