How DNS Works, iterative and recursive queries

Here's a high-level overview of how DNS works:

DNS Hierarchy: DNS operates in a hierarchical structure. At the top of the hierarchy, there are the root servers, followed by top-level domain (TLD) servers (such as .com, .org, .net), and then authoritative name servers responsible for individual domains.

Recursive DNS Resolution: When you enter a domain name into your web browser, your device (usually your computer or router) starts the DNS resolution process by querying a recursive DNS resolver (also known as a recursive resolver) provided by your internet service provider (ISP) or another third-party DNS resolver like Google Public DNS or Cloudflare DNS.

Recursive Query: The recursive resolver takes the domain name you entered and queries the root DNS servers to find the authoritative name servers responsible for the TLD (.com, .org, etc.). The root DNS servers respond with a referral to the appropriate TLD name servers.

Response: The authoritative name servers respond to the recursive resolver with the IP address, and the recursive resolver caches this information for a certain period of time (Time-to-Live, TTL).

Client Response: Finally, the recursive resolver returns the IP address to your device, allowing your browser to connect to the web server hosting the requested website.

DNS Iterative Queries: In the process mentioned above, each query from the recursive resolver to the root servers, TLD servers, and authoritative servers is an iterative query. Iterative queries are queries in which the DNS resolver sends a query to a server and expects the server to respond with either the answer or a referral to a more authoritative server. The recursive resolver continues making iterative queries until it reaches the authoritative name servers and gets the IP address for the requested domain.

In summary, DNS operates through recursive queries performed by the resolver on behalf of the client, and iterative queries are used by the resolver to traverse the DNS hierarchy and find the authoritative name servers.