What Is DNS and How It Works?

What Is DNS and How It Works

The Domain Name System (DNS) is a hierarchical and decentralized naming system of the Internet. A critical component of the digital infrastructure, it acts like a phonebook for the web. Just as phonebooks convert people’s names, which are easy for humans to remember, into phone numbers that machines use to connect calls, DNS converts human-friendly computer hostnames into machine-friendly IP addresses.

To access a website, we typically use familiar and recognizable domain nameslike example.com. However, for our computers to display the website, they must convert this name into something much harder for us to remember — such as 93.184.215.14 in the case of the IPv4 system. And with the newer IPv6 system — which is designed to eventually replace IPv4 — the addresses are even more complex, like 2606:2800:21f:cb07:6820:80da:af6b:8b2c. DNS is the system that performs this crucial conversion.

How Domain Name System Works

The Internet is vast, decentralized, and, most importantly, dynamic. For this reason, the Domain Name System has to be far more complex than a simple phonebook that anyone can keep a copy of. For one thing, it’s impractical for your computer to store billions of DNS records about every website that exists, just in case you might visit a few.

Additionally, the Internet is constantly changing: new websites pop up, and old ones disappear literally every second. To keep such an Internet “phonebook” up to date, your computer would need to store hundreds of gigabytes of DNS data and continuously monitor changes across the web. This would be incredibly wasteful.

Instead, DNS provides a far more efficient solution: a hierarchical system of DNS servers that store information about which IP addresses correspond to specific domain names. This system can be accessed by any computer that needs to convert a hostname to IP address. DNS has been in continuous operation for nearly 40 years, since its inception in 1985, ensuring that domain name resolution is both scalable and reliable.

Different Roles of DNS Servers

The domain name resolution process involves several DNS servers, each performing a specific function. Before we explore in detail how a domain name is converted into an IP address, it’s important to understand the roles of the various name servers. This will help clarify how DNS operates efficiently across the global network of networks that is the Internet.

• Recursive resolver (also called recursive name server or DNS recursor): This server receives the DNS query from the client, such as the user’s browser, and either answers the query using its cache or forwards it to other servers to get the correct IP address. The resolver plays a crucial role in simplifying the DNS lookup process for the end user.
• Root name server: This DNS server is the starting point in the process of resolving human-readable domain names into IP addresses. It directs the recursive resolver to the appropriate top-level domain (TLD) name server based on the domain zones, such as .com, .net, .org, or others.
• Top-level domain name server (TLD name server): This server is responsible for maintaining information about domain names within a specific top-level domain, such as .com, .net, .org, or others. It helps direct queries to the authoritative name server for the requested domain.
• Authoritative name server (authoritative DNS server): This server contains the actual DNS records, such as A, MX, or CNAME records, for a specific domain. It provides the final answer to the recursive resolver, containing the IP address that corresponds to the requested domain name.

It’s worth noting that all the servers involved in converting domain names into IP addresses are often simply referred to as DNS servers or name servers, without specifying their roles. However, for the purpose of this text, we will explicitly refer to them by their specific functions.

Example of a DNS Lookup

Now that we’ve defined all the necessary terms, let’s walk through the process of converting a domain name into an IP address step by step, using qrator.net as an example.

1. User request. When you enter qrator.net in your browser's address bar and press Enter, your computer sends a request to a recursive DNS resolver to find the corresponding IP address for the domain.
2. Recursive DNS resolver. The resolver, which is often managed by your ISP or a public DNS provider, checks its cache to see if it has recently resolved qrator.net. If it doesn’t have the answer cached, it begins the process of querying other DNS servers.
3. Querying the root name server. When the recursive resolver doesn’t have the answer, it queries a root name server. The root server doesn’t provide the IP address but instead directs the resolver to the TLD name server responsible for the specific domain zone, which in this case is .net.
4. Querying the TLD name server. The recursive resolver then sends a query to the TLD name server responsible for .net domains. This server doesn’t know the specific IP address of qrator.net, but it directs the resolver to the authoritative name server that holds the DNS records for qrator.net.
5. Querying the authoritative name server. The recursive resolver contacts the authoritative DNS server for qrator.net. This server contains the actual DNS records, including the A record, which maps the domain name to an IP address. The authoritative server responds to the resolver with the IP address of qrator.net.
6. Returning the IP address to the client. The recursive resolver provides your browser with the IP address that corresponds to qrator.net. With this information, the browser can now establish a connection to the web server hosting qrator.net.
7. Website loading. Using the IP address, your browser sends a request directly to the web server hosting qrator.net. The server responds by sending the requested webpage, and the website is displayed in your browser.

In cases where the requested address includes a subdomain, such as docs.qrator.net, the resolution process must involve an additional authoritative DNS server that stores records for the subdomains of the qrator.net domain.

As you may have noticed, the DNS lookup process resembles dealing with bureaucracy and involves considerable back and forth. However, because computers and networks are fast and (mostly) error-free, the Domain Name System, unlike human bureaucracy, works effectively.

In reality, a DNS lookup usually happens within milliseconds, ensuring a seamless browsing experience. Additionally, DNS caching at various points (such as in your browser, operating system, or the recursive resolver) helps speed up future queries for frequently visited websites.

Protection from DDoS Attacks on DNS Servers

Because of their critical role, DNS servers are frequent targets of Distributed Denial of Service (DDoS) attacks aimed at overwhelming servers and disrupting the functioning of digital infrastructure.

Without a way to convert domain names into IP addresses, the resources that users request become effectively unreachable, even if the web servers hosting them are perfectly operational. However, protection of DNS servers is often overlooked, making them a weak link in an organization’s cybersecurity defenses.

To protect DNS servers from attacks, specialized tools like Qrator.SecureDNS service offer robust defense mechanisms. An integral part of our enterprise solutions for a business’s continuous online availability, this distributed and reliable cloud DNS service ensures minimal response times and provides a high level of protection against even the most complex and intensive DDoS attacks.