The Domain Name System (DNS)

The Domain Name System (DNS) serves as a bridge between user-friendly domain names, such as example.com, and machine-readable IP addresses. A domain name may consist of a primary domain with an optional subdomain, for instance, www.example.com. When your device needs to resolve a hostname to an IP address, its DNS resolver will issue multiple queries until it obtains a response.

Basic Illustration

Imagine you want to access wikipedia.com through your web browser. Here’s the process in detail:

1. Your web browser sends a request to the DNS server specified in your network configuration.
2. The DNS server queries a root nameserver to locate the .com domain and receives information from the Top-Level Domain (TLD) servers.
3. Subsequently, it inquires with the TLD servers about the location of wikipedia.com and gets a response from the authoritative nameservers for Wikipedia’s hosting.
4. The DNS server then fetches the IP address of Wikipedia's web server.
5. With this information, your browser can connect to the web server and load the Wikipedia page.

Stored Responses

To enhance performance, local DNS servers may cache previous query results for a specific duration, referred to as TTL (Time To Live). Thus, if the same domain is queried shortly thereafter, the server can quickly supply the IP address without repeating the full resolution process.

Important Reminder: Modifications to DNS records may take time to propagate throughout the entire internet, potentially requiring up to 24 hours.