Module 1: DNS Fundamentals

DNS is the reason you type github.com instead of 140.82.121.4. It's also the reason entire companies go dark when a single provider has a bad day — ask anyone who was on-call during the Dyn attack in October 2016.

This module covers the fundamentals. Not as a dry technical taxonomy, but as the working knowledge you need to make good decisions, debug real problems, and stop treating DNS as someone else's problem.

What you'll cover

Lesson 1 — Introduction: Where DNS came from, why the phone book analogy is both useful and wrong, and what actually breaks when DNS fails at scale.

Lesson 2 — Architecture: The tree structure, the 13 root servers (sort of), how delegation works, and why the whole thing is surprisingly resilient.

Lesson 3 — Records: A practitioner's guide to every record type that matters. What each one does, when to use it, and the mistakes that cost you sleep.

Lesson 4 — Resolution: The full query journey. Recursive vs iterative. Caching. TTLs. What actually happens when you type google.com.

Lesson 5 — Protocols: UDP, TCP, port 53, the 512-byte limit, EDNS0, zone transfers. The plumbing you need to understand when things get weird.

Lesson 6 — Governance: ICANN, registries, registrars, WHOIS, RDAP. Who controls DNS and what that means in practice.

Lesson 7 — Hands-on: Set up a working DNS server. Run your own resolver. Learn by doing what reading cannot teach you.

Prerequisites

Comfortable with the command line. Basic networking concepts (IP addresses, TCP/UDP). That's it.

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Let's start at the beginning: a 1987 RFC that changed everything.