DNS: Resolving Names

Before a browser can open a connection to api.example.com, something has to turn that name into an address, and DNS, the Domain Name System, is that something. Almost every request starts with it, so knowing how it works explains slow first loads, changes that seem to take hours, and a family of outages that are "always DNS".

The topic starts with the hierarchy of servers that resolve a name and walks through one lookup step by step. It then covers the common record types, the TTL that controls caching, and the transports DNS runs over. An example plans a server move around the TTL, and a gotcha explains why a CNAME cannot sit at the root of a domain.

Running your own authoritative servers and securing DNS with DNSSEC are not covered.

By the end you can order the steps of a lookup, choose a record type, predict from a TTL when a change is seen, read dig output, and say when DNS uses TCP.