Communication Networks

This chapter explains how modern communication networks such as the Internet work, and considers the security risks due to its way of working. Basic concepts such as layered architectures, services and protocols, and the functions of the five layers of the Internet architecture are defined. It is characteristic of the Internet that each layer has its own addressing schemes for identifying the senders and receivers of messages sent within that layer The Internet then relies heavily on having a trustworthy service DNS which maintains information about the relationships between the names of systems and the placement of these systems within the Internet. The functioning of the two central Internet protocols TCP and IP and their interaction with the DNS is illustrated with examples.