How does DNS actually work?

How does DNS actually work?

DNS (Domain Name System) is a distributed and hierarchical system that translates human-readable domain names into the numerical IP addresses used by computers to communicate on the internet. Here's a step-by-step overview of how DNS works:

  1. User enters a domain name: When a user enters a domain name, such as "," in their web browser, their computer initiates a DNS lookup to find the corresponding IP address.

  2. Local DNS cache lookup: The computer first checks its local DNS cache, which stores previously resolved domain names and their corresponding IP addresses. If the requested domain name is found in the cache and hasn't expired, the IP address is retrieved, and the process ends.

  3. Recursive DNS resolver: If the domain name is not found in the local cache, the computer sends a request to a recursive DNS resolver. This resolver is typically provided by the user's Internet Service Provider (ISP) or a third-party DNS provider.

  4. Iterative DNS resolution: The recursive resolver starts the iterative resolution process. It contacts root DNS servers to find the authoritative DNS server responsible for the top-level domain (TLD) of the requested domain name. For example, it queries the root server to find the authoritative server for the ".com" TLD.

  5. TLD authoritative DNS server: The recursive resolver receives a response with the IP address of the authoritative DNS server for the TLD. It then sends a query to that server, requesting the IP address of the next level domain server.

  6. Authoritative DNS server for the domain: The recursive resolver contacts the authoritative DNS server for the specific domain (e.g., "") and sends a query for the IP address of the domain name.

  7. Response and caching: The authoritative server responds to the recursive resolver with the IP address of the requested domain. The recursive resolver caches this information to speed up future queries and sends the IP address back to the user's computer.

  8. User access to the website: Armed with the IP address, the user's computer can establish a direct connection to the web server hosting the website associated with the domain name. The web server responds to the user's request, and the website content is displayed in the user's web browser.

DNS is designed to be highly distributed, which helps improve its reliability and performance. The hierarchical structure and caching mechanisms ensure efficient resolution of domain names while reducing the load on authoritative DNS servers.

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