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Computer Networks/Networks Ra Professiona University

Notes Unit 12: Application Layer

CONTENTS
Objectives
Introduction

12.1 Domain Name System (DNS)
12.2 Electronic Mail
12.2.1 Simple Mail Transfer Protocol (SMTP)

12.2.2 Mail Exchange
12.3 World Wide Web
12.3.1 WWW Functioning
12.3.2 Browser Architecture
12.3.3 Hypertext Markup Language (HTML)

12.3.4 Uniform Resource Locators (URL)
12.4 Multimedia
12.4.1 Multimedia Elements

12.4.2 Uses of Multimedia
12.5 Summary
12.6 Keywords
12.7 Review Questions
12.8 Further Readings

Objectives

After studying this unit, you will be able to:
Know how DNS is able to provide the quick translation of text of the IP addresses into
corresponding binary numbers?

Learn about e-mail and its various features
Know Hyper Text Transfer Protocol and its role in accessing the websites

Conceptualize the World Wide Web
Understand the concept of multimedia and its elements
Introduction

The upper three layers namely session, presentation and application layers are considered as
user or application layers of the OSI models. They are implemented in software. In most of the
protocols, the functions of these layers are converged into a single layer called the application
layer. TCP is one of the examples of such types of protocols. The application layer, the highest
layer of OSI model interacts with software applications, which enable source and destination
machines to communicate properly. It provides different services, which are described herein.

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