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Understanding the DNS Resolution Process - How Domain Names Turn into IP Addresses

When you type a website address into your browser, DNS (Domain Name System) works behind the scenes to translate that name into an IP address your computer can use. This process is called DNS resolution and involves several steps with different types of queries and caching techniques to make everything fast and efficient.

Recursive vs. Iterative DNS Queries

  • Recursive Queries: Your DNS resolver asks a server for a complete answer. If the server doesn't know, it queries other DNS servers on your behalf until it finds the IP address, then sends it back to your resolver. The server does the heavy lifting here.

  • Iterative Queries: The resolver asks the server for the best answer it currently has. If it doesn't have the full answer, it points the resolver to another DNS server to ask next. The resolver then continues the search by querying the next server itself.

DNS Caching and TTL (Time To Live)

To speed up DNS lookups, servers and resolvers cache the answers they get from previous queries. This means if someone else recently asked for the same website, the DNS server can respond instantly from its cache instead of querying other servers again.

Each cached DNS record has a TTL, a timer that tells how long the record stays valid in the cache. When TTL expires, the cached record is deleted to avoid using outdated information.

Negative Caching: Handling Non-Existent Domains

DNS also caches negative responses — when a domain or record doesn't exist. This prevents repeated queries for the same missing site, reducing server load and improving overall performance.

In Summary

The DNS resolution process uses recursive and iterative queries to find the IP address for a domain name. Caching with TTL speeds up lookups by reusing previous answers, while negative caching prevents repeated requests for missing domains. Together, these mechanisms keep the internet fast and reliable.