DNS - Domain Name System

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Definition

Domain Name System (DNS)
Enables the translation from a human-readable domain name to a machine-readable IP address

Example
google.com -> 142.251.167.100

Command
nslookup (e.g., $ nslookup google.com)

Algorithm

Operates using a recursive, hierarchical lookup, sequentially querying each domain level until the authoritative record is retrieved.

From Wikipedia

In given example

1. The user attempts to access fr.wikipedia.org, triggering a DNS resolution request.
2. The DNS resolver queries the root NS, or root name server (here a.root-servers.net) to identify .org top-level domain authority.
3. root NS (a.root-servers.net) replies specifying the authoritative server for .org domain names (here a0.org.afilias-nst.info).
4. The resolver queries said server (a0.org.afilias-nst.info) for fr.wikipedia.org.
5. a0.org.afilias-nst.info answers ns0.wikimedia.org is in charge of wikipedia.org domain.
6. The resolver queries ns0.wikimedia.org for fr.wikipedia.org's IP address.
7. ns0.wikimedia.org returns 91.198.174.232.
8. The resolver delivers the IP address to the end user.

Note : In the referenced diagram, the DNS resolver is labeled Serveur DNS récursif

Structure

The DNS architecture is based on a distributed, tree-like model, structured around root servers, top-level domains, and authoritative name servers.

From Wikipedia