DNS (Domain Name System) is a critical component of the internet that translates human-readable domain names, like “example.com,” into IP addresses that computers and servers use to identify each other on the internet. DNS plays a crucial role in facilitating the accessibility and functionality of websites and other online services.
User Initiates a Request: When you enter a domain name (e.g., “www.example.com“) into your web browser’s address bar or click on a link, your computer initiates a DNS request to resolve that domain name into an IP address. This request is sent to a DNS resolver, which can be provided by your internet service provider (ISP) or configured independently.
Local DNS Cache Check: Your computer first checks its local DNS cache to see if it already knows the IP address associated with the requested domain name. If the information is found in the cache and has not expired, the computer uses it, saving time and resources. This local cache helps reduce the need for repeated DNS lookups.
Recursive DNS Resolver: If the IP address is not found in the local cache or has expired, the request is sent to a recursive DNS resolver, also known as a recursive DNS server. Recursive resolvers are operated by ISPs or third-party DNS providers (e.g., Google DNS, OpenDNS).
Root DNS Servers: The recursive DNS resolver, not having the IP address for the requested domain name, starts the resolution process by contacting one of the 13 root DNS servers distributed worldwide. These root servers contain information about top-level domains (TLDs), such as “.com,” “.org,” “.net,” and country-code TLDs like “.uk” or “.jp.”
TLD DNS Servers: Based on the TLD of the requested domain (e.g., “.com”), the root server refers the resolver to the authoritative DNS servers responsible for that specific TLD. There are many authoritative DNS servers for each TLD.
Authoritative DNS Servers: The authoritative DNS servers for the TLD then direct the recursive resolver to the authoritative DNS servers for the second-level domain (SLD), which is the part of the domain name just before the TLD (e.g., “example.com”).
Domain’s DNS Records: The authoritative DNS servers for the SLD contain the domain’s DNS records, including the A record (IPv4 address) and AAAA record (IPv6 address) that map the domain name to the corresponding IP address.
Response to Resolver: The authoritative DNS servers send the IP address back to the recursive resolver.
Resolver Caches the Result: The recursive resolver caches the IP address obtained from the authoritative DNS servers for future use, reducing the need for repeated lookups. It also sends the IP address to your computer.
Computer Accesses the IP Address: Armed with the IP address, your computer can now initiate a connection to the web server associated with the domain name. The web server processes the request and sends the requested webpage or resource back to your computer, which is then displayed in your web browser.
DNS operates behind the scenes, making the internet more user-friendly by translating human-readable domain names into the numerical IP addresses that computers and servers understand. This process occurs rapidly and seamlessly each time you access a website, ensuring that you can navigate the internet using familiar domain names instead of complex IP addresses.