Business Data Communications and Networking, Eleventh Edition

CHAPTER 4

DATA LINK LAYER

THE DATA link layer (also called layer 2) is responsible for moving a message from one computer or network device to the next computer or network device in the overall path from sender or receiver. It controls the way messages are sent on the physical media. Both the sender and receiver have to agree on the rules, or protocols, that govern how they will communicate with each other. A data link protocol determines who can transmit at what time, where a message begins and ends, and how a receiver recognizes and corrects a transmission error. In this chapter, we discuss these processes, as well as several important sources of errors.

OBJECTIVES

• Understand the role of the data link layer
• Become familiar with two basic approaches to controlling access to the media
• Become familiar with common sources of error and their prevention
• Understand three common error detection and correction methods
• Become familiar with several commonly used data link protocols

CHAPTER OUTLINE

4.1 INTRODUCTION

4.2 MEDIA ACCESS CONTROL

4.2.1 Contention

4.2.2 Controlled Access

4.2.3 Relative Performance

4.3 ERROR CONTROL

4.3.1 Sources of Errors

4.3.2 Error Prevention

4.3.3 Error Detection ...