Turning a Name into an Address
The Domain Name System translates a human name like a shop dot example into the numeric IP address a machine dials. Your browser cannot route on letters, so a lookup must happen before any connection opens.
The Chain of Questions
When a name is not already cached, your computer asks a recursive resolver, usually run by your provider. The resolver then walks the tree from the top.
- It asks a root server which servers own the top level domain such as com.
- It asks the top level domain server which servers own the example zone.
- It asks the authoritative server for the exact address record of the name.
Caching the Result
Each answer carries a time to live so the resolver and your computer can remember it. The next lookup for the same name skips the whole walk until that timer expires.
Key idea
A DNS lookup walks from root to top level domain to authoritative server, and caching with a time to live keeps later lookups for the same name fast.