# What is the Domain Name System (DNS)?

> The Domain Name System (DNS) is a distributed, hierarchical naming system, database, and query-response protocol.

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## Content

It associates domain names with typed data in resource records. Address records help applications locate services, but DNS also publishes mail-routing, delegation, service, verification, and other information; it is not simply an internet phone book.

A client normally asks a recursive resolver for a name and record type. The resolver may answer from cache or follow delegations through the DNS hierarchy to authoritative servers, then cache the result according to its time to live. The global DNS uses the public root; private DNS uses a different naming context.

### Key points

- **Distributed authority:** Administrators control zones, and delegations connect them to the hierarchy without placing all data in one database.
- **Typed records:** A, AAAA, MX, NS, CNAME, TXT, and other record types have different purposes; one name can have multiple records.
- **Resolver role:** Recursive resolvers perform resolution for clients, while authoritative servers publish data for zones; either may loosely be called a DNS server.
- **Important limitation:** A DNS response tells a client what the consulted DNS system returned. By itself, it does not prove that the destination is safe, authenticate unsigned data, encrypt the query path, or guarantee that cached information is current beyond its defined caching rules.

### Related terms

[Domain Name System (DNS) security](<https://yellowcube.eu/glossary/domain-name-system-security/>) · [Dynamic DNS (DDNS)](<https://yellowcube.eu/glossary/dynamic-dns/>) · [Dynamic Host Configuration Protocol (DHCP)](<https://yellowcube.eu/glossary/dynamic-host-configuration-protocol/>) · [Domain Name System (DNS) hijacking](<https://yellowcube.eu/glossary/domain-name-system-hijacking/>) · [Domain Name System (DNS) cache poisoning](<https://yellowcube.eu/glossary/domain-name-system-cache-poisoning/>)

### Sources

[IETF RFC 1034: Domain Names—Concepts and Facilities](https://datatracker.ietf.org/doc/html/rfc1034) · [IETF RFC 1035: Domain Names—Implementation and Specification](https://datatracker.ietf.org/doc/html/rfc1035) · [IETF RFC 9499: DNS Terminology](https://datatracker.ietf.org/doc/html/rfc9499)

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