Humans remember domain names (google.com) but network protocols use IP addresses (142.250.191.78). Without a translation system, users would need to memorize numeric addresses for every website.
A distributed hierarchical system that translates human-readable domain names into IP addresses, acting as the internet’s phonebook.
- Application requests IP for a domain name (e.g., google.com)
- DNS resolver checks cache, then queries root servers, TLD servers, and authoritative servers
- Responses are cached to improve performance
- Primarily uses UDP for queries (port 53) due to speed requirements
- Falls back to TCP for large responses (zone transfers) or when UDP is blocked
- Hierarchical distributed database
- Uses UDP primarily (fast, low overhead) with TCP fallback
- Caching reduces query latency and server load
- Critical infrastructure — internet unusable without it
- Built from: UDP — primary transport protocol used
- Built from: Application Layer — operates at this layer
- Related: IP Protocol — returns IP addresses
- Related: DNS Cache — improves performance
- DNS cache poisoning can redirect users to malicious sites
- DNS over HTTPS (DoH) encrypts queries for privacy
- Zone transfers use TCP, not UDP, due to large data sizes