Lesson 3 - Token Ring and FDDI

   Introduction

In the last lesson, we saw that Ethernet's approach to medium access is similar to an informal conversation. Each node simply begins transmitting as soon as the bus is idle, then takes corrective steps in case of a collision. In contrast, a Token Ring network avoids collisions altogether. It does this by using a system similar to a formal meeting, in which a "speaking stick" is passed from one person to the next. A person may speak only when holding the stick. If a person is holding the stick but has nothing to say, she passes the stick on to someone else.

   Objectives

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

1.	Explain the basics of Token Ring medium access and operation
2.	Describe how Token Ring medium access differs from Ethernet
3.	Describe common Token Ring configurations
4.	Explain key differences between Token Ring and Fiber Distributed Data Interface (FDDI) (pronounced "fiddee") networks

Key Point
A Token Ring node may transmit only when it has a free token.

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