This course provides a comprehensive introduction to the fundamentals of computer and telecommunication networks. It begins with an exploration of networked devices and the standardisation of networking functions through the OSI 7-Layer model. The course delves into the first four layers of the OSI model, examining a variety of network types including the Internet, Wi-Fi, mobile networks (3G/4G/5G, and prospective 6G), and optical fiber networks. The course further explores the principles of IP addressing and routing, equipping students with the knowledge to design networks for both residential and industrial settings. A key component of the course is the study of teletraffic engineering fundamentals, with a focus on traffic theories and their implications for network design and quality of service (QoS). Practical lab sessions provide students with the opportunity to design networks and analyse their performance using computer simulators. Additionally, a project component offers designing a realistic enterprise network. This course aims to equip students with a robust understanding of computer and telecommunication networks fundamentals and practical skills in network design and analysis.