What actually happens during DNS resolution

When a browser opens an address, the name is not turned into an IP by a single query but by a chain of them. Let us walk that chain step by step.

The stub resolver

The operating system ships a minimal resolver that never talks to the root servers itself. It hands the query to a recursive resolver whose address came from DHCP or from manual configuration.

The recursive resolver

This is where the real work happens:

1. it checks its own cache;
2. it queries a root server when no cached answer exists;
3. it walks down the zone hierarchy to the authoritative server.

What TTL controls

TTL states how many seconds an answer may be considered valid.

example.com.   300   IN   A   203.0.113.10

A value of 300 means five minutes. Too low a TTL raises load; too high a TTL slows migrations down.