DNS (Domain Name System) is a hierarchical, distributed naming system for internet resources. It maps human-readable names like example.com to the IP addresses, mail servers, and other data that computers use to route traffic.
How DNS Resolution Works
Browser → Local resolver → Root servers → TLD (.com) servers → Authoritative nameservers- Browser checks local cache → OS cache
- Queries DNS resolver (ISP or 8.8.8.8)
- Resolver queries root servers for TLD authority
- Queries TLD servers for domain’s nameservers
- Queries authoritative nameservers for the specific record
- Returns answer; resolver caches for TTL duration
Key Components
| Component | Role |
|---|---|
| Root servers | 13 root server clusters, top of the hierarchy |
| TLD servers | Handle .com, .org, .net, etc. |
| Authoritative nameservers | Your DNS provider — holds your actual records |
| Recursive resolver | Your ISP or 8.8.8.8 — does the leg work |
DNS vs HTTP
DNS is a prerequisite for HTTP. Before your browser sends an HTTP request, it must resolve the hostname to an IP via DNS. DNS lookups typically add 20-120ms to the first connection if not cached.