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Part 1: Introduction to networking
Chapter 1: Introduction to TCP/IP networking
So, you are new to networking, Like many people, your perspective about networks might be that of a user of network, as opposed to the netword engineer who builds the networks. For some, your view of networking might be based on how use the internet, from home, using a high-speed Internet connection like digital subscriber line or cable TV, as shown in figure 1-1.
The top part of the figure shows a typical high-speed cable internet user. The PC connects to a cable modem using an ethernet cable. The cable modem then connects to a cable outlet in the wall using a round coaxial cable the same kind of cable used to connects your TV to the CATV wall outlet. Because cable Internet services provide service continuously, the user can just sit down at the pc and star sending email, browsing websites, making internet phone calls, and using tools and applications.
The lower part of the figure uses two different technologies. First, the tablet computer uses wireless technology that goes by the name wireless local-area network. Instead of using an ethernet cable. In this example, the router uses a different technology, DLS, to communicate with the internet.
Both home-based and networks build for use by a company make use of similar networking technologies. The infomation technology world refers to a network created by one corporation, or enterprise, for the purpose of allowing its employees to communicate, as an enterprise network. The smaller networks at home, when used for business porpose, often go by the name small office/home networks.
Users of enterprise networks have some idea about the enterprise network at their company of school. People realize that they usea network for many tasks. PC uses might realize the PC connects through an ethernet cable to a matching wall outlet, as shown at the top of figure. Those same users might use wireless LANs with they laptop when going to a meeting in the conference room as well. Figure shows these two end user perspectives on an enterprise network.

Note: In networking diagrams, a cloud represents a part of a network whose details are not important to the purpose of the diagram. In this case, Figure ignores the details of how to create an enterprise network.

Some users might not even have a concept of the network at all. Regardless of how much you already about how networks work, this book and the related certification help you how networks do their job. That job is simply this: moving data from device to another. The rest of this chapter, and the rest of this first part of the book, reveals the basics of how to build enterprise networks so that they can deliver data between two devices

*TCP/IP Networking Model
A networking model, sometimes also called a netwoking arcbitecture of networking blueprint, refers to a comprehensive set of a network; callectively, these documents define everything that should happen for computer network to work. Some documents define a protocol, which is a set of physical requirements for networking. For example, a documents could define the voltage and current levels used on a particular cable when transmitting data.
You can think of a networking model as you think of architectural blueprint for building a house. Sure, you can build this house without blueprint. However, the blueprint can ensure that the house has the right foundation and structure so that it will no fall down, and it has the correct hidden spaces to accommodate the plumbing, electrical, gas, and so on. Also, the many different people that build the house using the blueprint such as framers, electricicans, bricklayers, painters, and so on know that if thay follow the blueprint, their part of the work should not cause for the other workers.
Similarly, you could build your own network write your own solfware, build your own networking cards, and so on to create a network. However. it is much easier to simply buy and use the products that already conform to some well-known network model of blueprint. Because the networking product vendors build their products with some networking model in mind, their products should work well together.

* History leading to TCP/IP
Today, the world of computer networking uses one networking model: TCP/IP. However, the workd has not always been so simple. Once upon a time, networking protocols did't exist, including TCP/IP. Vendors created the first networking protocols; these protocols supported only that vendors computers.
For example, IBM, the computer company with the largest market share in many markets back in the 1970s and 1980s, published its system network architectural networking models in 1974. Orther vendors also created their own proprietary networking models. As a resuilt, if your company bought computers from three vendors, network engineers often had to create three different networks based on the networking models created by each networking company. and then somehow connect those networks, making the combined networks much more complex. The left side of figure shows the general idea of what a companys enterprise network might have looked like back in the 1980s, before TCP/IP became common in enterprise internetworks.

Although, vendors defined proprietary networking models often worked well, having an open, vendor-neutral networking model would aid competition and reduce complexity. The international Organization for Standardization took on the task to create such a model, starting as early as the late 1970s, begining work on what would become known as the Open system interconnection networking model. ISO had a noble goal for the OSI model: to standardize date networking protocols to allow communication among all computers across the entire planet. ISO worked toward this ambitious noble goal, with particpants from most of the technologycally developed nations on earth participating in the process.
A second, less-formal effort to create an open, vendor-neutral, public networking model sprouted forth from a US. Derpartment of Defense contract. Researchers at various universities volunteered to help further develop the protocols surrounding the original DoD work. These efforts resulted in a competing open networking model called TCP/IP.
During the 1990s, companies began adding OSI, TCP/IP, or both to their to their enterprise networks. However, by the end of the 1990s, TCP/IP had become the common choise, and OSI fell away. The center part of figure shows the general idea behind enterprise networks in that decade still with networks built upon multiple networking models but including TCP/IP.
Here in the twenty-first century, TCP/IP dominates. Proprietary networking models still exist, but the mostly been discarded in favor of TCP/IP. The OSI model, whose develment suffered in part because of a slower formal standardization process as compared with TCP/IP, never succeeded in the marketplace. And TCP/IP, the networking model originally created almost entired by a bunch of volunteers, has become the most prolific network model ever, as shown on the right side of figure.
In this chapter you will read about some of the basics of TCP/IP.Although you will learn facts about TCP/IP, the true goal of this chapter is to help you understand what a networking model or networking architectural really is and how it works.
Also in this chapter, you will learn about some of the jargon used with OSI. Will any of you ever work on a computer that is using the full OSI protocols instead of TCP/IP? Probably not. However, you will often use terms relating to OSI.

*Overview of the TCP/IP networking model
The TCP/IP model both defines and references a large collection of protocols that allow computers to communicate. To define a protocol, TCP/IP uses documents called Requests For Comments (RFC). The TCP/IP models also avoids repeating work already done by some standards body or vendors consortium by simply referring by standards of protocols created by those groups. For example, the Institute of Electrical and Electronic Engineers (IEEE)