Networking Fundamentals

A top-down networking course. We follow one concrete question - what happens when you load https://example.com? - and answer it layer by layer, from the application down to the bits on the wire. The skeleton mirrors Computer Networking: A Top-Down Approach (Kurose & Ross).

Read it start to finish, or jump to a topic. Interactive artifacts appear where watching something move beats reading about it.

The journey

1. The Internet & performance - what a network is, and how we measure it.
2. Application layer - HTTP, DNS, and the modern web.
3. Transport layer - ports, UDP, and how TCP makes an unreliable network reliable.
4. Network layer (data plane) - IP addressing, subnetting, NAT.
5. Network layer (control plane) - how routers learn paths.
6. Link layer - MAC addresses, ARP, switches, Ethernet.
7. Wireless & mobile - WiFi and cellular.
8. Security - cryptography, TLS, firewalls.
9. At scale - load balancing and CDNs.
10. Tooling & debugging - reading ping/dig/tcpdump/ss/curl output, and a symptom-to-cause playbook.
11. Cloud & production networking - VPCs, security groups, NAT gateways, and private connectivity, kept cloud-generic.
12. Reference - ports, latency numbers, header field maps, and decision rules for the classic tradeoffs.

Start with The Internet & Performance.