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History Leading to TCP/IP

Today, the world of computer networking uses one networking model: TCP/IP. However,
the world has not always been so simple. Once upon a time, networking protocols didn’t
exist, including TCP/IP. Vendors created the first networking protocols; these protocols
supported only that vendor’s computers. For example, IBM published its Systems Network
Architecture (SNA) networking model in 1974. Other vendors also created their own proprietary
networking models. As a result, 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 company, and then somehow connect those networks, making
the combined networks much more complex. The left side of Figure 1-3 shows the general
idea of what a company’s enterprise network might have looked like back in the 1980s,
before TCP/IP became common in enterprise internetworks.
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Figure 1-3 Historical Progression: Proprietary Models to the Open TCP/IP Model
Although vendor-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 (ISO) took on the task to create such a model,
starting as early as the late 1970s, beginning work on what would become known as the Open
Systems Interconnection (OSI) networking model. ISO had a noble goal for the OSI model: to standardize data networking protocols to allow communication among all computers across
the entire planet. ISO worked toward this ambitious and noble goal, with participants from
most of the technologically 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 U.S. Department of Defense (DoD) 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 enterprise networks.
However, by the end of the 1990s, TCP/IP had become the common choice, and
OSI fell away. The center part of Figure 1-3 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 they have mostly been discarded in favor of TCP/IP. The OSI model, whose
development 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 entirely by a bunch of volunteers, has become the most prolific
network model ever, as shown on the right side of Figure 1-3.

In this chapter, you will read about some of the basics of TCP/IP. Although you will learn
some interesting facts about TCP/IP, the true goal of this chapter is to help you understand
what a networking model or networking architecture 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.

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