CISCO CCNA 200-301 - Chapter 1: Introduction to TCP/IP Networking

Welcome to the first chapter in your study for CCNA! This chapter begins Part I, which
focuses on the basics of networking.
Networks work correctly because the various devices and software follow the rules. Those
rules come in the form of standards and protocols, which are agreements of a particular
part of how a network should work. However, the sheer number of standards and protocols
available can make it difficult for the average network engineer to think about and work
with networks—so the world of networking has used several networking models over time.
Networking models define a structure and different categories (layers) of standards and protocols.
As new standards and protocols emerge over time, networkers can think of those new
details in the context of a working model.
You can think of a networking model as you think of a set of architectural plans for building
a house. A lot of different people work on building your house, such as framers, electricians,
bricklayers, painters, and so on. The blueprint helps ensure that all the different pieces of the
house work together as a whole. Similarly, the people who make networking products, and
the people who use those products to build their own computer networks, follow a particular
networking model. That networking model defines rules about how each part of the network
should work, as well as how the parts should work together so that the entire network functions
correctly.
Today, TCP/IP rules as the most pervasive networking model in use. You can find support for
TCP/IP on practically every computer operating system (OS) in existence today, from mobile
phones to mainframe computers. Every network built using Cisco products today supports
TCP/IP. And not surprisingly, the CCNA exam focuses heavily on TCP/IP. This chapter uses
TCP/IP for one of its main purposes: to present various concepts about networking using the
context of the different roles and functions in the TCP/IP model.