Module 4:
Networks & Internet Infrastructure

Module 4 explains how Internet traffic moves through the physical and organizational infrastructure of the global network. It begins with IP addresses and routing, showing that once DNS identifies a destination, devices still need a way to reach it. The module explains IPv4 and IPv6, public and private IP addresses, routers, routing tables, and the routing process that allows packets to move across many connected networks.

The module then examines Internet service providers, network tiers, undersea cables, satellites, and data centers. It shows that the Internet is a network of networks built by ISPs, autonomous systems, exchange points, peering and transit relationships, and large-scale routing cooperation. It also explains that most global traffic travels through fiber-optic and submarine cables, while satellites help extend connectivity to remote areas. Finally, it describes data centers, cloud infrastructure, hyperscale facilities, and edge systems as the physical backbone that stores data and powers modern digital services. Overall, the module presents the Internet not as something abstract or “in the cloud,” but as a vast system of addresses, routers, providers, cables, satellites, and computing facilities that make worldwide digital communication possible.