Have you ever wondered how your computer is able to connect to a website by simply typing in its name? This is where the Domain Name System (DNS) comes into play.
DNS is like a phone book for the internet, converting human-readable domain names into IP addresses that computers can understand. In this article, we will explore how DNS servers work step by step.
Step 1: Understanding the Basics of DNS
DNS works on a client-server model. When you enter a domain name in your web browser, your computer acts as the client and sends a request to a DNS server. The DNS server then looks up the IP address associated with that domain name and returns it to your computer.
Step 2: Resolving the Domain Name
The first thing your computer does is check its local cache for the IP address of the domain name you entered. If it finds a match, it directly connects to that IP address without involving any external DNS servers.
If there’s no match in the local cache, your computer sends a query to its configured DNS server, usually provided by your Internet Service Provider (ISP). This is known as a recursive query because if the configured DNS server doesn’t have the answer, it will recursively reach out to other DNS servers until it finds an answer or reaches a root DNS server.
Step 3: Contacting Root DNS Servers
If the configured DNS server doesn’t have the IP address for the requested domain name, it contacts one of the root DNS servers. These root servers are responsible for maintaining information about top-level domains such as .com, .org, and country-specific domains like .uk or .fr.
The root DNS server doesn’t have detailed information about every website but can direct your computer to other authoritative DNS servers that can provide the required information.
Step 4: Contacting Top-Level Domain (TLD) DNS Servers
Based on the information received from the root DNS server, your computer then contacts the appropriate Top-Level Domain (TLD) DNS server. TLD servers are responsible for specific domain extensions like .com or .org.
The TLD server further directs your computer to the authoritative DNS server responsible for the specific domain name you entered.
Step 5: Contacting Authoritative DNS Servers
The authoritative DNS server is the final stop in resolving a domain name. It has detailed information about a particular domain, including IP addresses of the associated web servers and other records like MX records for email routing.
Once your computer reaches the authoritative DNS server, it retrieves the IP address associated with the requested domain name and sends it back to your computer.
Step 6: Caching and Storing Information
Your computer caches this IP address locally so that future requests to the same domain name can be resolved quickly without having to go through all these steps again. The TTL (Time-to-Live) value associated with each record determines how long this information is retained in the cache before it expires.
Step 7: Establishing Connection
Armed with the IP address obtained from the authoritative DNS server, your computer can now establish a connection with the web server hosting the website you want to access. This connection allows you to fetch and display web content in your browser.
In Conclusion
DNS servers play a crucial role in translating human-readable domain names into machine-readable IP addresses. By understanding how DNS works step by step, you can appreciate its significance in enabling seamless internet browsing.
By now, you should have a clear understanding of the DNS resolution process and the role of various DNS servers involved. Next time you enter a domain name in your browser, remember that behind the scenes, a complex series of queries and responses are taking place to bring that website to your screen.