1.1. The Network Abstraction: Why Networks Exist

💡 First Principle: A network exists to move data from one place to another reliably and efficiently. Every networking technology, protocol, and device is designed to solve one of three problems: addressing, delivery, or reliability.

What breaks without this understanding: You memorize isolated facts instead of building reasoning tools. When the exam presents an unfamiliar scenario, you guess rather than deduce. Understanding why networks exist helps you reason about any network technology—when you encounter an unfamiliar protocol or device, ask: "Which of the three fundamental problems does this solve?" The answer guides you to the correct response.