All computer devices on the Internet, whether your personal smartphone or content servers powering the world’s largest e-commerce websites, use numbers to locate and interact with one another. You don’t need to recollect and input a long number whenever you open an internet browser and visit a website.
The DNS is essentially the Internet’s phonebook. DNS locates the corresponding Internet Protocol (IP) address when a user enters a domain name like “google.com” or “nytimes.com” into a web browser. Browsers use these addresses to directly contact the website’s primary server or a content delivery network’s edge server.
Types of DNS servers
There are four types of DNS servers, each with specific functions: recursive resolvers, authoritative nameservers, root nameservers, and top-level domain name servers. These DNS servers collaborate to resolve a service user’s needs for an IP address of a specified domain. They are:
Recursive resolver DNS server
In a domain name system inquiry, the first server contacted is the recursive resolver. This DNS server facilitates communication between a user and a DNS nameserver.
Upon obtaining a DNS query from an internet browser, the recursive resolver will respond with cached data or initiate a request to a root nameserver. Then, the following request to a TLD nameserver and a query to the authoritative nameserver. The recursive resolver then responds to the client with the IP address they requested after receiving a response containing the address from the authoritative nameserver.
The recursive resolver caches all results it gets from authoritative nameservers. It saves time by serving records directly from their cache rather than contacting the nameservers when multiple clients request the same IP address.
Root nameservers
The recursive resolver is familiar with the 13 DNS root nameservers and uses them as a starting point for looking up DNS information. When a recursive resolver sends a query that contains a domain name, the root nameservers take it and return a response that specifies which top-level domain (TLD) nameserver the recursive resolver should contact (.com, .net, .org, etc.).
The ICANN (Internet Corporation for Assigned Names and Numbers), a non-profit organization, is responsible for maintaining the root nameservers. Therefore, it suffices to state that while there are Thirteen root nameservers, it does not imply only thirteen computers are in the root nameserver network.
Faster answers are possible because of Anycast routing, and each of the 13 different root nameservers exists in several locations. By estimation, there are approximately 600 unique root nameservers today.
TLD Nameservers
TLD nameservers store data for all domains with the same domain extension, such as .com, .net, or any other extension that follows the last dot in a URL. For all domains that end in “.com.” After getting a response from the root nameserver, the recursive resolver would contact a “.com” TLD nameserver for the domain google.com.
The “.com” TLD nameserver would then point the recursive resolver to the authoritative nameserver for the domain google.com.
The Internet Assigned Numbers Authority (IANA), a division of ICANN, is responsible for the administration of TLD nameservers. According to the Internet Assigned Numbers Authority (IANA), there are five categories of TLD servers. They are as follows:
Generic top-level domain
The most well-known examples of generic top-level domains (TLDs) include “.com,” “.org,” “.net,” “.edu,” and “.gov,” none of which has any connection with any country.
TLDs with country codes
This type of TLD DNS is for countries or sovereign entities. It ends with an abbreviation of the country. For instance, .uk, .us, .ru, and .jp.
Sponsored TLD DNS
These TLDs frequently stand for ethnic, professional, or regional communities. The sponsor of the TLD (sponsored TLD) represents that community. For instance, Google sponsors the TLD “.app,” aimed at the developer community. Also, “.gov” is sponsored by the General Services Administration and is meant for the United States government.
Dedicated TLDs:
Certain TLDs are permanently unavailable since they are on the reserved list. For instance, “.localhost” and “.example” are only used in local computing environments and example demonstrations.
Authoritative Nameservers
A TLD nameserver’s response to a recursive resolver will point toward an authoritative nameserver. The final stop on the resolver’s path to an IP address is typically the authoritative nameserver.
When a domain has a CNAME record (alias), the authoritative nameserver will provide the recursive resolver with an alias domain. It can also provide the server’s IP address in the DNS A record. The authoritative nameservers from Cloudflare DNS include Anycast routing to increase their dependability.