LECTURE HANDOUT Computer Networks

Abstract

Mastering computer networks and communication protocols is now an essential skill for any engineer in applied sciences. In an era of interconnected systems, where the fast, reliable, and secure transmission of data has become a necessity, understanding the underlying mechanisms of networks is crucial for designing, operating, and maintaining highperformance infrastructures. This textbook, entitled “Computer networks”, is intended for third-year Electronics students at the École Supérieure en Sciences Appliquées de Tlemcen (ESSA-Tlemcen), where it has been taught since 2023. This course requires prior knowledge in computer tools, computer system architecture, and communication systems.The primary objective of this course is to provide students with a comprehensive understanding of computer networks, their architectures, and the protocols that govern communication between systems. The course addresses not only theoretical concepts but also their implementation in real environments to ensure both conceptual and practical training. The course particularly emphasizes: • The layered architecture of networks and how each layer interacts with the others, • The protocols that ensure various functions (addressing, routing, error control, reliability), • The current technologies and standards used in wired and wireless networks, • Practical application through case studies to develop operational skills. The course content is structured into several progressive chapters, allowing a coherent skillbuilding approach: • Chapter 1: Introduction to Computer Networks This first chapter introduces the fundamental concepts: definitions, objectives, a historical overview of communications and the evolution of the Internet. It also presents the8 different classifications of networks (by geographic scope, topology, speed, and transmission mode), providing a global view of current architectures. • Chapter 2: Layered Architecture and the OSI Model This chapter introduces the principle of layered structuring, the notions of protocol, service, and interface, as well as the advantages of hierarchical architectures. A detailed analysis of the OSI model and its seven functional layers is carried out, highlighting their roles and interactions. • Chapter 3: The Physical Layer This chapter covers the general characteristics of physical transmission, transmission modes, bandwidth and speed, as well as transmission media (cables, optical fibers, wireless links). This part provides the essential hardware foundations for understanding binary communication over a channel. • Chapter 4: The Data Link Layer This chapter highlights the crucial role of this layer in ensuring reliable exchanges. It addresses data encapsulation into frames, error control mechanisms, media access control (CSMA/CD, CSMA/CA, token passing), and physical addressing (MAC). Major protocols such as Ethernet are studied. • Chapter 5: The Network Layer This section deals with logical addressing (IPv4), subnetting concepts, IP routing principles and mechanisms, as well as routing protocols (static and dynamic). This chapter is essential for understanding how data travels through multiple interconnected networks. • Chapter 6: The Transport Layer This part focuses on the TCP and UDP protocols, their characteristics, segmentation concepts, multiplexing/demultiplexing, as well as flow control and transmission reliability. • Chapter 7: Session, Presentation, and Application Layers Finally, this chapter explores the upper layers of the OSI model: session management, data translation, encryption and compression, as well as application services and protocols such as HTTP, FTP, SMTP, DNS.9 Each chapter is accompanied by practical examples to consolidate understanding through the manipulation of studied concepts (frame analysis, IP address configuration, network architecture studies, protocol testing, etc.). This textbook combines theory and practice. Concepts are introduced progressively and illustrated with explanatory diagrams, concrete examples, and exercises. The practical aspect is strongly emphasized, enabling students to apply the concepts studied. In short, this course aims to provide future engineers with a global vision of computer networks while developing their ability to design, configure, and secure interconnected systems.