DNS

DNS, or Domain Name System, is a hierarchical distributed naming system for computers, services, or resources connected to the Internet or a private network. Its primary function is to translate human-friendly domain names into numerical IP addresses that machines use to identify each other. DNS also stores other information associated with domain names, such as mail servers and service endpoints, via various resource records.

When a user attempts to reach a domain, a DNS resolver (usually operated by the user's ISP or an enterprise) performs a recursive lookup on behalf of the client. The resolver queries a sequence of name servers in a top-down manner: starting at the root zone, then the top-level domain (such as .com or .org), and finally the domain’s authoritative name servers. Answers are cached to speed subsequent queries and reduce network load, with records carrying a time-to-live (TTL) value that governs caching duration.

DNS data is organized into zones and represented by resource records. Common record types include A (IPv4 address), AAAA (IPv6 address), CNAME (alias), MX (mail exchanger), NS (name server), SOA (start of authority), PTR (reverse lookup), and TXT (text information). An authoritative name server stores the definitive DNS data for a zone.

Security and privacy measures include DNSSEC, which authenticates origin and data integrity, and transport-level encryption approaches such as DNS over HTTPS (DoH) and DNS over TLS (DoT) to improve privacy. DNS is administered through standards coordinated by the Internet Engineering Task Force (IETF) and policy bodies such as ICANN and IANA.