How does the Domain Name System (DNS) work?

The Domain Name System (DNS) is a hierarchical decentralized naming system that translates domain names (e.g., www.example.com) into IP addresses (e.g., 192.0.2.1) that computers can understand. It acts as a phonebook of the internet, allowing users to access websites and other internet resources using human-readable domain names instead of remembering complex IP addresses.

When a user enters a domain name in their web browser, the DNS resolution process begins. Here is a step-by-step explanation of how DNS works:

1. User Input: The user enters a domain name (e.g., www.example.com) in their web browser.

2. Local DNS Resolver: The user's device sends a DNS query to the local DNS resolver, which is typically provided by the Internet Service Provider (ISP) or configured manually. The local DNS resolver is responsible for handling DNS queries on behalf of the user.

3. Recursive Query: If the local DNS resolver does not have the IP address corresponding to the domain name in its cache, it starts a recursive query process. It sends the query to the root DNS servers.

4. Root DNS Servers: The root DNS servers are the highest level of DNS servers in the hierarchy. They maintain a database of the IP addresses for the top-level domain (TLD) servers (.com, .org, .net, etc.). The root DNS servers respond to the query with the IP address of the TLD server responsible for the requested domain extension (.com in this case).

5. TLD DNS Servers: The local DNS resolver then sends a query to the TLD DNS server responsible for the requested domain extension (.com). The TLD DNS server maintains information about the authoritative DNS servers for each domain registered under its TLD.

6. Authoritative DNS Servers: The TLD DNS server responds with the IP address of the authoritative DNS server for the requested domain (example.com). The authoritative DNS server is responsible for storing the DNS records for the specific domain.

7. DNS Records: The local DNS resolver sends a query to the authoritative DNS server for the IP address of the requested domain (www.example.com). The authoritative DNS server responds with the corresponding IP address.

8. DNS Response: The local DNS resolver receives the IP address from the authoritative DNS server and stores it in its cache for future use. It then sends the IP address back to the user's device.

9. Website Access: The user's device now has the IP address of the requested domain. It can establish a connection with the web server hosting the website and retrieve the requested web page.

Overall, the DNS system works by distributing the responsibility of maintaining the mapping between domain names and IP addresses across multiple DNS servers in a hierarchical manner. This distributed nature ensures efficient and reliable resolution of domain names to IP addresses, enabling seamless internet connectivity.