Trust
Mechanisms that work by believing an answer, with nothing to prove the answer is honest
Part 3 · Inside one network
11Spanning Tree — the protocol that fixes a problem Ethernet createdWhy one redundant cable can take down a whole network, how Radia Perlman solved it in 1985, what is in the 35-byte BPDU, and every step of the development from 802.1D to what replaced it
Part 3 · Inside one network
13ARP — the seam the whole stack rests its trust onThe question ARP actually asks is not the one people think, a cache rule from 1982 that is still in force, why every packet is nearly a third empty padding, and why there is nothing at all to verify
Part 4 · Across networks
14Routing — what the gateway actually does nextNineteen articles on this site mention routes, and none explained how a router decides. This one answers with a single rule you can measure on your own machine
Part 6 · The services that make it usable
20DHCP — to ask for an address you need an addressThe chicken-and-egg problem an RFC posed in 1985, why it takes four messages, why 81 percent of the header is still legacy nobody uses, and reading a real packet off your own machine
Part 6 · The services that make it usable
23TLS — HTTPS does not mean safeThe three promises the RFC makes and the four people think it makes, this site's real certificate chain, the name check that carries the whole thing alone, and what stays visible even once encrypted
Part 6 · The services that make it usable
24Certificate lifetimes — why only 47 days47 days is not a tightening of the screws. It is an admission that revocation never worked — and the 200-day ceiling has been in force since March 2026