4 min read · Dec 20, 2023
Have you ever wondered what happens when you type a web address into your browser’s address bar and hit Enter? The process that unfolds behind the scenes is known as DNS (Domain Name System) lookup. In this blog post, we’ll take you through the intricate steps involved in the DNS lookup process, shedding light on how your browser connects to a website seamlessly.
The process begins when you, the user, enter a URL (Uniform Resource Locator) into your web browser’s address bar. For example, let’s consider the URL “www.example.com."
Your browser checks its local cache to see if it already has a recent DNS resolution for the requested domain. If it finds a match, it can skip the rest of the lookup process and use the cached IP address, expediting the connection.
If the DNS resolution isn’t found in the browser’s cache, the browser may check your operating system’s DNS cache. Operating systems like Windows and macOS maintain their own DNS caches for efficiency. If the DNS record is present here, it’s promptly returned to the browser.
In certain network configurations, a proxy server may come into play. Your browser could send the DNS query to a proxy server instead of directly to the router or local DNS resolver. This intermediary, the proxy server, manages the connection between your browser and the DNS resolver.
If no proxy server is involved, the request is sent to your local router or DNS resolver, often provided by your Internet Service Provider (ISP). The router may have its own cache to expedite DNS queries. If the required information is available, it’s provided directly to your browser.
If the router’s cache doesn’t contain the DNS record, it queries any locally configured private DNS servers within your Local Area Network (LAN). These servers may be set up within a corporate network.
If the private DNS server can’t resolve the domain name, it forwards the request to your ISP’s recursive DNS resolver. This resolver is responsible for handling DNS queries for the ISP’s customers and often maintains a substantial cache of DNS records.
Should the ISP’s DNS resolver lack the necessary information, it contacts a Root Name Server, one of the 13 authoritative root servers worldwide. The root server provides essential information about top-level domains (TLDs), like “.com,” “.org,” “.net,” and more. The root server responds by referring the query to the appropriate TLD server.
The TLD server manages requests for domains under its specific TLD, such as “.com” or “.org.” It provides the IP address of the authoritative name server for the second-level domain, like “example.com.”
The authoritative name server for the requested domain, such as “example.com,” may have multiple IP addresses. These multiple IPs serve as a form of redundancy and load balancing, ensuring reliability and performance. The DNS resolver receives these IPs and selects one based on factors like proximity, availability, or load.
In addition to multiple IP addresses, some authoritative name servers employ GeoDNS techniques. GeoDNS provides different IP addresses based on the geographic location of the user making the DNS query. This optimizes performance and delivers geographically relevant content by directing users to the nearest data center, reducing latency and enhancing the user experience.
The ISP’s recursive DNS resolver caches the IP address obtained from the authoritative name server, including multiple IP addresses if applicable. It then returns this information to the private DNS server in your LAN.
The private DNS server caches the IP address, which may be one of the multiple IP addresses obtained earlier, and forwards it to your router.
The router caches the IP address and provides it to your browser.
Your browser receives the IP address, potentially one of several, for the requested domain. It then uses this IP address (also remembering it for future references) to establish a connection to the web server associated with that domain, ultimately loading the webpage you requested.
Understanding the DNS lookup process is like unveiling the magic behind your browser’s ability to seamlessly connect you to the vast world of websites. This intricate journey involves various layers of caching, authoritative servers, and even geographic optimization, all working together to make your web experience smooth and efficient.
To gain an even deeper insight into this fascinating process, you should also watch our informative video, where each step is vividly illustrated and explained.
Happy browsing!
