CCNA新教程第2章.pdf

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Composite Default screen CertPrs8 / CCNA Cisco work Associate Study Guide / Deal / 222934-9 / Chapter 2
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2
Networking
Concepts
CHAPTER OBJECTIVES
OSI Reference Model work Model
Data Link Layer ✓ Two-Minute Drill
Layer Q&A Self Test
Transport Layer
Transferring Information
puters
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Composite Default screen CertPrs8 / CCNA Cisco work Associate Study Guide / Deal / 222934-9 / Chapter 2
2 Chapter 2: Networking Concepts
efore considering how to configure Cisco routers and switches, you must be
introduced to working concepts you’ll need to understand in order to grasp
Bthe advanced concepts discussed in later chapters. The OSI Reference Model is the
best place to start, since it will help you understand how information is transferred between
networking devices. Of the seven layers in the OSI Reference Model, be especially sure to
understand how the bottom three layers function, since working devices function at
these layers. This chapter discusses information flow, as well as Cisco’s three-tiered hierarchical
model, which is used to design scalable, flexible, and easy-to-troubleshoot-and-works.
CERTIFICATION OBJECTIVE
OSI Reference Model
The anization for Standardization (ISO) developed the Open Systems
Interconnection (OSI) Reference Model to describe how information is transferred
from one machine to another, from the point when a user enters information using a
keyboard and mouse to when that information is converted to electrical or light signals
transferred along a piece of wire or radio waves transferred through the air. It is
important to understand that the OSI Reference Model describes concepts and terms
in a general manner, and that work protocols, such as IP and IPX, fail to fit
nicely into the sc