How the Internet Actually Works
You use the internet for everything. Do you actually know how it works?
This four-part series covers the foundations of the internet — from the Cold War military project that started it all, through the systems that make it function today, to the 60-year history behind every cloud VM you’ve ever launched. It’s written for practitioners and aspiring engineers who want to understand the infrastructure they work on, not just use it.
Each article includes practical commands you can run from your own terminal, interview questions with senior-level answers, and the career context that connects history to the skills employers pay for.
From ARPANET to Your Router
The Cold War problem that created packet switching. TCP/IP and the protocol that connected incompatible networks. The physical internet — 550 submarine cables, Internet Exchange Points, and the tier system that holds it all together. BGP, CDNs, and why things break in spectacular ways. Plus: why the internet was designed to be decentralised, and what that means for self-hosting.
How DNS Actually Works (And Why It’s Always DNS)
From the HOSTS.TXT file maintained by one person at Stanford, to a distributed hierarchy serving billions of queries. How DNS resolution actually works — root servers, TLD servers, authoritative servers, and caching. Record types that matter in practice. The “propagation” myth debunked. Real failure scenarios from 20 years of troubleshooting. DNS privacy and why running your own resolver matters.
What Happens When You Type a URL
The most common interview question in infrastructure, answered at senior level. Ten steps from keystroke to rendered page: browser cache, DNS, TCP handshake, TLS negotiation, HTTP request, routing, reverse proxy, server processing, response, and browser rendering. Every step is a potential failure point. Every step has tools to diagnose it.
The Birth of Cloud Computing: From MIT Time-Sharing to Hyperscalers
Cloud computing didn’t start with AWS — it started in 1961 at MIT. Time-sharing, IBM’s first hypervisor in 1966, Multics, Unix, VMware’s inflection point, AWS selling spare capacity, OpenStack’s ambitious promise, and the container revolution. A 60-year timeline that explains why every cloud platform works the way it does — and why self-hosting is closer to the original vision than the hyperscaler monoculture.
Career Value: Infrastructure interviews test your understanding of these fundamentals constantly. “How does the internet work?” “Walk me through a DNS lookup.” “What happens when you type a URL?” “What’s the difference between virtualisation and containerisation?” The depth of your answers reveals your level. This series gives you the senior answers.
Who This Series Is For
- Career changers building foundational knowledge before their first infrastructure role
- Junior engineers who use these systems daily but want to understand what’s actually happening underneath
- Homelabbers who want context for the services they’re running — DNS, reverse proxies, containers, VMs
- Senior engineers who want a refresher or a resource to share with their teams
- Interview candidates preparing for networking, infrastructure, or DevOps roles
Related Guides
This series covers the theory and history. These guides cover the hands-on:
- How to Build Your First Homelab in 2026 — Put this knowledge into practice
- Raspberry Pi 5 Homelab: 10 Projects — Docker, DNS, Kubernetes, and more on real hardware
- Pi-hole on Raspberry Pi 5 — Run your own DNS resolver
- Nginx Proxy Manager — Build a reverse proxy
- K3s Kubernetes — Container orchestration at home
- Best Mini PCs for Homelabs — Run Proxmox on enterprise hardware
- Why Self-Host in 2026 — The sovereignty case
The internet is infrastructure. Understanding it — really understanding it — makes you better at everything built on top of it.
ReadTheManual is run, written and curated by Eric Lonsdale.
Eric has over 20 years of professional experience in IT infrastructure, cloud architecture, and cybersecurity, but started with PCs long before that.
He built his first machine from parts bought off tables at the local college campus, hoping they worked. He learned on BBC Micros and Atari units in the early 90s, and has built almost every PC he’s used between 1995 and now.
From helpdesk to infrastructure architect, Eric has worked across enterprise datacentres, Azure environments, and security operations. He’s managed teams, trained engineers, and spent two decades solving the problems this site teaches you to solve.
ReadTheManual exists because Eric believes the best way to learn IT is to build things, break things, and actually read the manual. Every guide on this site runs on infrastructure he owns and maintains.
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