What is the DNS?A Complete Guide on DNS Operation

What exactly is DNS?

The Domain Name System (DNS) is the Internet’s phonebook. Domain names, such as nytimes.com or espn.com, are used by humans to access information online. Web browsers communicate using Internet Protocol (IP) addresses. DNS converts domain names to IP addresses so that browsers can access Internet resources.

Each Internet-connected device has a unique IP address that other machines can use to locate the device. DNS servers reduce the requirement for humans to remember IP addresses like 192.168.1.1 (in IPv4) or more complex modern alphanumeric IP addresses like 2400:cb00:2048:1::c629:d7a2 (in IPv6).

How does DNS function?

DNS resolution is the process of translating a hostname (such as www.example.com) into a computer-friendly IP address (such as 192.168.1.1). Each device on the Internet is assigned an IP address, and that address is required to locate the relevant Internet device, much as a street address is used to locate a certain residence. When a user requests a webpage, a translation must take place between what the user types into their web browser (example.com) and the machine-friendly address required to access the example.com webpage.

To comprehend the process of DNS resolution, it is necessary to first learn about the many hardware components that a DNS query must transit through. Apart from the initial request, the DNS query occurs “behind the scenes” in the web browser and requires no input from the user’s computer.

When a webpage is loaded, four DNS servers are involved:

DNS recursion – Consider the recursor to be a librarian who is asked to locate a specific book in a library. The DNS recursor is a server that receives queries from client machines via applications like web browsers. The recursor is then often responsible for making further requests to satisfy the client’s DNS query.

The root nameserver is the initial stage in translating (resolving) human-readable host names into IP addresses. It’s similar to a library index that links to different book racks – normally, it serves as a reference to other more particular locations.

TLD nameserver – Think of a top-level domain server (TLD) as a specific rack of books in a library. This nameserver is the following step in the search for a certain IP address, and it hosts the final portion of a hostname (the TLD server in example.com is “com”).

Authoritative nameserver – Think of this last nameserver as a dictionary on a book rack, where a specific name can be translated into its description. The last stop in the nameserver inquiry is the authoritative nameserver. If the authoritative name server has access to the requested record, it will return the IP address for the requested hostname to the DNS Recursor (the librarian) who initiated the request.

What is the distinction between a recursive DNS resolver and an authoritative DNS server?

Both notions refer to servers (or groups of servers) that are part of the DNS infrastructure, but each serves a different purpose and dwells in separate parts of the DNS query pipeline. One way to think about it is that the recursive resolver is at the start of the DNS query, while the authoritative nameserver is at the finish. 

DNS recursive resolver

The recursive resolver is the machine that responds to a client’s recursive request by searching for the DNS record. It accomplishes this by a series of requests until it reaches the authoritative DNS nameserver for the requested record (or times out or returns an error if no record is found). Fortunately, recursive DNS resolvers do not always need to make many queries to find the records required to respond to a client; caching is a data persistence technique that aids in short-circuiting the necessary requests by serving the requested resource record earlier in the DNS lookup. 

DNS authoritative server

Simply said, an authoritative DNS server is a server that stores and manages DNS resource records. This is the server at the end of the DNS lookup chain that will respond with the requested resource record, allowing the web browser to reach the IP address required to access a website or other web resources. Because it is the last source of truth for specific DNS records, an authoritative nameserver can satisfy queries from its data without needing to query another source. It’s worth noting that if the query is for a subdomain, such as foo.example.com or blog.cloudflare.com, an additional nameserver will be added to the sequence following the authoritative nameserver, which is responsible for holding the CNAME record for the subdomain.

What steps are involved in a DNS lookup?

In most cases, DNS is concerned with translating a domain name into the proper IP address. To understand how this process works, trace the course of a DNS lookup from a web browser to the DNS lookup process and back again. Let us go over the steps.

Please keep in mind that DNS lookup information is frequently cached, either locally on the querying computer or remotely in the DNS infrastructure. A DNS lookup typically consists of eight phases. When DNS information is cached, steps in the DNS lookup process are bypassed, making it faster.