DNS.
also: domain name systemThe internet's phone book: it translates domain names like www.example.com into the IP addresses computers use.
the two-minute refresher
- A lookup walks resolver → root → TLD → authoritative server, and answers are cached along the way.
- Record types include A (IPv4), AAAA (IPv6), CNAME (alias) and MX (mail).
- TTLs decide how long answers are cached, and so how fast a DNS change takes effect.
- DNS can steer traffic: geo-routing, weighted records and failover between regions.