This text helps readers to take their first steps in the world of computer networks and Internet in particular. It is conceived as a study tool for an introductory course in “Computer Networks” in Engineering and Computer Science bachelor courses, but its structure makes it suitable for use in any type of school where the objective is to provide introductory technical knowledge of the world of Internet. The text is made up of three parts: (i) networks and protocols, (ii) Internet, (iii) access networks.

The first part defines the basic network nomenclature and introduces the world of protocols through its layered architecture that represents the supporting framework. The fundamental concepts that characterize the various types of network are presented and the numerical parameters necessary to express their performance are defined. The methodological tools necessary to understand the mechanisms that regulate the operations of a network are then presented under the “Protocol theory” hat.

The second part is entirely dedicated to the world of Internet. The reader’s understanding of its technical content is facilitated by the so-called “top-down” introduction of the issues addressed. This consists in presenting the methods of interaction with the world of Internet from the user’s point of view, thus initially describing the protocols of the application layer, which make it possible to provide and receive all types of services through a network. We mention among these the e-mail and those applications that allow you to interact with the “World Wide Web”. The text then addresses the issues related to the transfer of information through the Internet network as required by applications, which requires the description of the transport layer and the network layer protocols.

The third part deals with the issue of access networks, that is those communication structures which allow “the entrance doors” to the Internet world to be reached. In particular, the link layer protocols are introduced and for the physical layer we limit ourselves to describing the techniques for encoding the information sent through a transmission medium. The issue of local area networks, which provide connectivity in limited geographical areas, such as office buildings and companies, is addressed with particular emphasis on the access protocols adopted. Finally, the main technological solutions in copper and fibre optics providing Internet access to a population distributed over a territory are presented.

We emphasise the original structure of this text, which has dedicated the entire chapter 3 to theoretical aspects of networks and their protocols, with reference to point-to-point connections (section A), multipoint networks (section B), routing protocols (section C) and flow and congestion control (section D). This feature makes it possible to adopt the text in university courses of different types in terms of the number of associated credits.

In courses with 10/12 ECTS credits dedicated to Internet and computer networks, the recommended course is to introduce the principles of networks with the first two chapters, followed by the presentation of the Internet protocols of chapters 4, 5 and 6. The theory (chapter 3) of point-to-point connections (section A) and of flow and congestion control (section D) can precede the discussion of the respective topics in the transport layer (chapter 5); the theory of the routing protocols (section C) may precede the treatment of these protocols in the network layer (chapter 6). The issue of access networks is addressed through chapters 7, 8 and 9. The theory of point-to-point connections (section A), if not previously discussed, can precede the discussion of chapter 7, and the theory of multipoint networks (section B) can be described before going into the topic of local networks (chapter 8)

In introductory university courses on networks with a limited number of credits, the discussion can focus on Internet protocols (chapters 4, 5 and 6), after the introductory part that provides the basic concepts on computer networks (chapters 1 and 2). The presentation of access networks (chapters 7, 8 and 9), which can also be limited to local networks only (chapter 8) or residential access networks only (chapter 9), can conclude the course. Specific aspects of protocol theory (chapter 3) can be treated to complement the study of the various Internet protocols and access networks, depending on the interest and objectives of the course.

The text is proposed as a tool for knowledge and systematic study of Internet and computer networks in general; for this reason it is accompanied by more than one hundred numerical examples which enable the operations carried out by the various protocols to be expressed quantitatively in terms of network performance parameters. No particular prerequisites for understanding the text are required, beyond basic knowledge of probability theory. Additional text and support material such as files for laboratory exercises, self-assessment tests for students, all images of the text to be used to deliver a course based on it, can be found on the website