DNS (Domain Name Server)

How Does It Work ?

The Domain Name System (DNS) is an essential part of the web that works invisibly to connect the easily-remembered names of websites typed into a search bar with their associated Internet Protocol (IP) addresses.

Although IP addresses can be used to access websites, domain names have become the preferred method of access due to their short, memorable nature. For instance, "Network World."

In the 1970s and 1980s, Elizabeth Feinler at Stanford Research Institute was responsible for keeping track of every computer linked to the internet and its unique IP address. Given the exponential expansion of the internet, this was obviously untenable; in 1983, Paul Mockapetris created DNS, an automated, scalable system that translates domain names to IP addresses.

Keeping track of the over 342 million domain names that are now registered in a single index would be a massive undertaking. The directory, like the internet itself, is stored on domain name servers all over the world that regularly communicate with one another to provide changes and remove duplications.

One of the motivations for developing a distributed system is the desire to improve performance. Imagine, for instance, that all of the simultaneous requests from around the world to connect the domain name google.com with its corresponding IP address were being processed in a single facility. In order to solve this problem, DNS data is distributed over multiple servers.

Therefore, it is possible for a single domain to use many IP addresses. To give just one example, when you type "www.google.com" into the address bar of your computer, tablet, or smartphone, you connect to a specific physical server. Nonetheless, DNS will always lead you to the correct location.

When a computer needs to know the IP address that corresponds to a domain name, it first does a DNS query, which is commonly performed via a web browser. The query then proceeds to a recursive DNS server, also known as a recursive resolver. A recursive resolver is often managed by an Internet Service Providers (ISP), such as AT&T or Verizon (or some other third-party), and it knows which other DNS servers it needs to contact to resolve the name of a site with its IP address. The servers that genuinely contain the relevant information are termed authoritative name servers.

DNS is organized in a hierarchy. An first DNS query for an IP address is performed to a recursive resolver. This search first leads to a root server, which holds information on top-level domains (.com, .net, .org), as well as country domains. Given that root servers can be found in any part of the world, the DNS system selects the one that is geographically nearest.

Once the request reaches the relevant root server, it moves to a top-level domain server (TLD nameserver), which keeps information for the second-level domain, which is the words that you type into a search box. The request then goes to a domain nameserver, which looks up the IP address and transmits it back to the DNS client device so it may visit the right website. All of this takes only milliseconds.