Lesson 3 - The Data Link Layer

   Introduction

The Data Link Layer is the second layer in the OSI reference model. It uses the signaling services of the Physical Layer below it. To Layer 3 above, it provides the service of addressing a message to a device located across a single physical transmission path. The physical path that connects two nodes is called a "link."

   Objectives

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

1.	Describe what a link is
2.	Name the main services of the Data Link Layer
3.	Explain the relationship between packets and frames
4.	Describe how each frame is addressed to its destination

Key Point
The Data Link Layer deals with frames over a single physical link. A Data Link Layer address is the unique address built into a NIC.

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