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Mit Professional Unit 7: Data Link Layer

Unit 7: Data Link Layer Notes

CONTENTS
Objectives
Introduction

7.1 Data Link Layer Design Issues
7.1.1 Services Provided to Network Layer
7.1.2 Framing

7.1.3 Error Control
7.1.4 Flow Control
7.2 Error Detection and Correction
7.2.1 Error Detection Codes
7.2.2 Error Correction Code

7.3 Summary
7.4 Keywords
7.5 Review Questions

7.6 Further Readings
Objectives

After studying this unit, you will be able to:
Explain the significance & functions
Discuss data link layer design issues including services provided to the network layer,
framing, error control and flow control
Describe error detection and correction techniques along with error-correcting codes and
error-detecting codes
Introduction

Data link layer is the second layer after physical layer in the OSI reference model. It describes the
techniques to access a shared communication channel and reliable transmission of data frame in
computer communication environment. It receives a raw stream of bits for the physical layer at
sender machine. The raw stream of data is created using different technologies like cable, DSL,
wireless, optical fiber, etc. The data link layer transforms data free of undetected transmission
errors to the network layer. Data link layer accomplishes this task by using acknowledgment
frames and error detection algorithms. In other words, the task of the data link layer is to
transmit the bits to the destination machine. The data link layer of the destination machine,
then, hand over thus received data to the network layer for processing. The communication
between any two hosts that are physically connected via a channel can be shown in Figure 7.1.

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