DNS, which stands for Domain Name System, is a fundamental protocol that enables users to access websites and other internet services using human-readable domain names like “example.com” instead of numeric IP addresses (e.g., 192.0.2.1). Understanding how DNS works is essential for anyone using the internet, as it plays a critical role in translating domain names into IP addresses, allowing the internet to function in a user-friendly manner.
Here’s a simplified explanation of how DNS works:
- Domain Registration: The process begins when someone registers a domain name through a domain registrar. This unique name is associated with one or more IP addresses where the website or service is hosted.
- DNS Records: After registering a domain, the domain owner sets up DNS records on a DNS server. These records contain information about the domain, such as the authoritative name servers responsible for the domain and the corresponding IP addresses associated with the domain name.
- Resolving a Domain: When a user enters a domain name in their web browser, their device needs to find the corresponding IP address to establish a connection with the website. The device first checks its local cache (memory) to see if it has recently resolved the domain. If the information is not in the cache or has expired, the device initiates a DNS query.
- DNS Query: The DNS query is sent to a recursive resolver (typically provided by the user’s ISP or a public DNS service like Google’s 8.8.8.8). The recursive resolver does not have the answer but will find it for the requesting device.
- Iterative Resolution: The recursive resolver starts the process of iterative resolution by first querying the root nameservers. The root nameservers know the IP addresses of the Top-Level Domain (TLD) nameservers (e.g., .com, .org, .net).
- TLD Nameservers: The recursive resolver then queries the appropriate TLD nameserver for the domain extension (e.g., .com) to get information about the authoritative nameservers responsible for that specific domain.
- Authoritative Nameservers: Once the recursive resolver obtains the IP addresses of the authoritative nameservers, it queries these nameservers directly.
- DNS Response: The authoritative nameservers respond with the correct IP address for the requested domain, and this information is passed back through the recursive resolver to the user’s device.
- Local Cache Update: The recursive resolver stores the IP address in its local cache for a specified time (TTL – Time To Live). This cache helps speed up future queries for the same domain and reduces the load on the DNS infrastructure.
- Establishing Connection: Armed with the correct IP address, the user’s device can now establish a connection with the web server hosting the requested website or service.
Overall, DNS acts as the “phone book” of the internet, translating easy-to-remember domain names into the numerical IP addresses necessary to locate and communicate with web servers. This process happens automatically and in the background every time you access a website, send an email, or perform any online activity using domain names.