MEPX
Chapter 1 of 10All chapters
  1. 1Layers
  2. 2Addresses
  3. 3DNS
  4. 4TCP and UDP
  5. 5Routing
  6. 6HTTP
  7. 7Wifi and local networks
  8. 8Latency and bandwidth
  9. 9Diagnosing problems
  10. 10How the internet fits together

Chapter 1 of 10

Layers

Why networking is split into levels.

The idea

Each layer solves one problem and hands the result to the next: cables and wifi at the bottom, addressing above that, reliable delivery above that, and applications at the top.

  • The point is independence: changing wifi for cable does not change the browser.
  • The four practical layers are link, internet, transport and application.

Where problems live

Naming a layer makes debugging quicker. No signal is a link problem, no route is an internet problem, a refused connection is transport, and a 500 error is the application.