Before considering how to configure Cisco routers and switches, you must be introduced to basic networking concepts you’ll need to understand in order to grasp the 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 most networking 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-maintain networks | OSI Reference Model Hierarchical Network Model Two-Minute Drill Data Link Layer Network Layer Transport Layer Transferring Information Between Computers CCNA CISCO CERTIFIED NETWORK ASSOCIATE 2 Networking Concepts k Q A Self Test 2 Chapter 2 Networking Concepts Before considering how to configure Cisco routers and switches you must be introduced to basic networking concepts you ll need to understand in order to grasp the 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 most networking 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-maintain networks. CERTIFICATION OBJECTIVE OSI Reference Model The International Organization 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 many network protocols such as IP and IPX fail to fit nicely into the scheme explained in ISO s model. Therefore the OSI Reference Model is most often used as a teaching and troubleshooting tool. By understanding the basics of the OSI Reference Model you can apply these to real protocols to gain a better understanding of them as well as to more easily troubleshoot problems. Advantages ISO developed the seven-layer model to help .
