DNS
acronymnetworking
Stands for: Domain Name System
The system that translates human-readable names like example.com into IP addresses.
The Domain Name System is the internet's phone book, a distributed, hierarchical lookup queried billions of times a second. Because so much depends on it, its speed (via anycast and caching) and its security (encrypted variants) are constant areas of work.
You meet DNS most often when something else is broken. A service is unreachable, the application team swears nothing changed, and the first useful question is whether the name resolves at all, whether it resolves to what you expect, and whether the answer came from cache or from the authoritative server. That is why dig and nslookup output is worth being able to read line by line rather than glancing at.
The part that surprises people is that DNS is not one lookup. A single page load can trigger resolution for a dozen names, each with its own TTL, each potentially answered by a different resolver in the path: the stub resolver on the host, the recursive resolver at the ISP or in the enterprise, and the authoritative servers for the zone. When an answer is wrong, the real question is usually which of those layers is holding it.
DNS also became a policy surface, not just a lookup service. Blocking, filtering, and redirection are frequently implemented at the resolver because it sits in front of everything, which is why enterprise security stacks and national blocking regimes both reach for it. The protocol was designed for reachability, and it has spent decades being used for control.
Also known as: dns, domain name system, name resolution