What is DNS?

The Domain Name System (DNS) is a foundational protocol of the internet that enables users to access websites, applications, and services using readable domain names instead of complex numerical IP addresses. Without DNS, every internet interaction would require manually entering IP addresses like 192.0.2.1 or 2001:db8::1.

In its simplest form, DNS acts as a distributed database. It stores and provides mappings between domain names and various forms of resource records—most commonly IP addresses, but also mail servers (MX), text records (TXT), and service discovery (SRV), among others.

DNS was designed to solve two primary problems:

1. Human usability: People can remember words (like google.com), not IPs.

2. Scalability: The internet's structure requires a hierarchical, globally distributed system to resolve billions of queries daily.

Technically speaking:

• DNS is a decentralized, hierarchical naming system.

• It operates over UDP (port 53) by default for queries, and TCP for zone transfers or large payloads.

• It uses caching to reduce resolution time and query load.

• It includes both forward resolution (name → IP) and reverse resolution (IP → name via PTR records).

Hierarchy Breakdown:

Root (.)
└── TLDs (com, org, net, tr)
    └── Domains (example.com)
        └── Subdomains (www.example.com)

Each layer in the hierarchy is handled by authoritative nameservers, and DNS resolution typically traverses from the root down to the most specific entry.

DNS is not just about websites:

• It powers email routing (MX records).

• It enables service discovery (SRV, SVCB).

• It supports security mechanisms (DNSSEC, CAA, TLSA).

• It's used in CDNs, firewalls, load balancers, and internal service meshes.