Summary
DNS is the hierarchical, distributed naming system that resolves domain names such as example.com into IP addresses, enabling users and applications to reach services by name rather than by numeric address.
What is DNS?
The Domain Name System works as a distributed database spread across a global hierarchy of name servers. When a client queries a domain name, a recursive resolver contacts authoritative name servers in sequence—starting from root servers, then top-level domain servers, and finally the authoritative server for the specific domain.
DNS supports multiple record types: A records map hostnames to IPv4 addresses, AAAA records to IPv6, CNAME records create aliases, MX records define mail servers, and TXT records hold arbitrary text used for verification and security policies such as SPF and DKIM.
In modern cloud and microservice architectures, internal DNS is equally important. Service discovery systems like Kubernetes CoreDNS or Consul use DNS to let services find each other dynamically without hardcoded IP addresses.
Why is DNS relevant?
- Usability: Allows services to be addressed by stable names independent of changing IP addresses
- Resilience: DNS-based load balancing and failover enable traffic to be redirected without client changes
- Security: DNSSEC and DNS-over-HTTPS protect queries from tampering and eavesdropping