Lesson 5 - LAN Software Architectures

   Introduction

In the first part of this unit, we discussed how networks differ at the Physical and Data Link Layers, through approaches such as Ethernet, Token Ring, and wireless LANs. In this lesson, we will examine the various software technologies that operate at Layer 3 and above. We will introduce the key elements and protocols of the most important network operating systems (NOSs), and compare the layered protocols of each NOS to the OSI model. In general, you will find that each PC LAN architecture maps fairly closely to the OSI model as shown here. However, you will also discover some notable departures from this system.

   Objectives

At the end of this lesson you will be able to:

1.	Explain the role of Network Basic Input/Output System (NetBIOS) and NetBIOS Extended User Interface (NetBEUI) (pronounced "net-Boo-ee")
2.	Describe the difference between the medium access control methods of Ethernet and AppleTalk
3.	Compare the TCP/Internet Protocol (IP) protocol stack to the OSI model

Key Point
Most LAN architectures conform largely to the OSI reference model. All major LAN architectures support TCP/IP.

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