DNS Hierarchy: What You Need To Know

The Domain Name System (DNS) makes it easy for people to browse the Internet. It turns simple website names, like mywebsite.com, into numbers that computers use to communicate with each other. Without it, you would type in a long string of numbers to open a simple web page. When you register a domain name, DNS plays a significant role by linking that name to the correct server, making it easy for people to find your website. Learning how the DNS hierarchy works is important because it shows the steps your device follows to find a website. Each level in the system plays a unique role in helping you reach your desired online destination. This blog explains each step of the DNS structure, showing you why every layer is important and how they all fit together.

KEY TAKEAWAYS

• DNS helps convert website names into IP addresses so computers can locate each other.
• The domain name system hierarchy moves through each step from the root level to the host server.
• Root servers direct requests to the correct top-level domain (TLD), such as .com or .org.
• Second-level domains are names people register (e.g., example in example.com).
• Subdomains organize different parts of a website under one main domain.
• Hosts are where the website’s data is stored and accessed.
• Root Zone servers are placed globally to make DNS fast, strong, and reliable.
• Understanding the DNS hierarchy helps you manage, troubleshoot, and protect websites more effectively.

What is The DNS?

The Domain Name System (DNS) is a hierarchical, decentralized naming system that translates human-friendly website names (e.g., hosted.com) into IP addresses (e.g., 192.0.2.1), which computers use to locate servers where that website is stored.

When you type a domain name into your browser, DNS resolves it to the correct IP address, allowing your device to connect to the right server. Without this system, people would have to memorize numerical IP addresses to visit websites, like needing a phone number for every call.

However, DNS simplifies this process, making the internet more user-friendly. As we move deeper into the DNS hierarchy, you will see how different parts of the Domain Name System work together to keep the internet running smoothly.

What are DNS Servers?

DNS servers are specialized systems that resolve human-readable domain names into machine-readable IP addresses. When you enter a website domain, your device sends a request to a DNS server, which looks up its records to find a matching IP address.

If the server has the answer cached (from a recent lookup), it responds immediately. If not, it performs a recursive query, asking other DNS servers (starting from the root, then the domain extension or Top Level Domain (TLD), and finally, the authoritative server for the domain) to find the correct IP.

Once resolved, your browser uses the IP to connect to the website’s server. DNS servers also improve speed through caching and can optimize traffic via load balancing (e.g., directing users to the nearest server).

What is a Fully Qualified Domain Name?

A Fully Qualified Domain Name (FQDN) is a complete and absolute address of a resource, such as a server, website, or network device, within the DNS. Unlike partial domain names (e.g., mail or mail.mydomain), an FQDN leaves no ambiguity about the resource’s location because it specifies every level of the DNS hierarchy, from the hostname to the domain name’s TLD.

For example, in the FQDN:  mail.mydomain.com
mail is the hostname (identifying a specific server or service)
mydomain.com is the domain name (the registered website address)

This structure ensures that DNS resolvers can accurately navigate from the top-level domain (.com) down to the exact host (mail).

FQDNs are essential for reliable network communication because they eliminate guesswork in DNS resolution. Without them, systems may rely on assumptions, such as appending default domain suffixes (e.g., automatically adding mydomain.com to mail), which could lead to errors if the intended resource resides elsewhere.

For instance, while mail may resolve correctly on a local office network, an FQDN like mail.mydomain.com guarantees the correct server is located, whether accessed internally or over the public internet.

Additionally, the role of FQDNs extends beyond just naming; they are fundamental to how DNS queries work. When you enter an FQDN (mail.mydomain.com) into a browser, the DNS resolver follows a structured process:

It starts by consulting the root DNS servers to identify the authoritative servers for .com, then queries the .com TLD servers to locate mydomain.com, and finally requests the IP address of mail from the domain’s authoritative name servers. This hierarchical resolution ensures efficiency and accuracy, preventing requests from being misrouted.

Moreover, FQDNs are universally compatible, functioning seamlessly across public internet services (e.g., www.google.com), private intranets (e.g., server1.corp.local), and cloud environments (e.g., api.region.cloudprovider.com). They are essential for web hosting, email delivery, and internal network management, where precise addressing is critical.

DNS Hierarchy Explained

The DNS hierarchy is the system that organizes how website names are translated into IP addresses. It works step-by-step, moving through different levels until the correct server is found. Each level plays a special role in ensuring you reach the right website quickly and without errors.

Root Level

The root level is the starting point of the DNS hierarchy. When you type a website address into your browser, the request first goes to the root servers. These servers do not know the final answer; they only know where to send your request next.

They direct it to the correct TLD server based on an extension like .com, .org, or .net. A small number of root servers worldwide are important for keeping the Internet running smoothly.

Top-Level Domain (TLD)

The next step after the root level is the Top-Level Domain, often called a TLD. These are the endings of website addresses (.com, .net, .org, .gov, and many others). TLD servers manage everything under their extension. For example, the .com server handles all domain names that end with .com. They help move the request closer to the correct website by pointing to the server that knows about the domain name.

Second Level Domain

Below the TLD is the Second Level Domain (SLD). This is usually the main name you choose when registering a website. For example, in myblog.com, myblog is the SLD. These domains are owned by individuals or companies and are registered through domain name service providers. The SLD then connects your website’s custom domain name with the internet.

Subdomain

A subdomain is a smaller part under a Second-Level Domain. It helps organize a website into different sections. For instance, blog.example.com is a subdomain of example.com. Subdomains are often used to create special areas of a website, such as stores, blogs, or help centers, without needing a completely new domain name. They give website owners more flexibility to easily manage different parts of their site.

Hosts

Hosts are the final step in the DNS hierarchy. A host refers to a specific device, server, or website that holds the information you want to access. Once the DNS system reaches the host level, your computer connects to where the website’s files are stored. Hosts are important because they provide the content you see when visiting a website.

Why DNS Hierarchy Matters

The DNS hierarchy is central to keeping the Internet organized and working well. Dividing responsibilities across different levels ensures that no single server or system has too much to handle.

This setup helps speed up lookups because your request is guided step by step instead of searching through every website on the internet. It also improves reliability because others can assist if one server is busy or offline.

The DNS hierarchy also makes website management easier. Owners can easily control their main domains and create subdomains for different parts of their sites. This structure keeps everything clear and well-organized, even when a site grows bigger over time.

Root Zone Servers

Root Zone servers are essential components of the DNS. While there are 13 root server names (designated from A to M), these aren’t individual physical servers; they represent clusters of hundreds of replicated server instances worldwide.

This network uses Anycast routing technology and is maintained by various trusted organizations, including Verisign, ICANN, NASA, universities, and other reputable institutions. It creates a resilient and efficient system.

When you enter a website URL, the DNS resolution process begins with these root servers. For example, if you access mystore.com, your request first reaches a root server instance. As discussed earlier, the root server doesn’t provide the final IP address.

Instead, it acts as a directory that points your request to the appropriate Top-Level Domain (TLD) server based on the website’s extension. The process works as follows:

1. Your resolver asks the root where to find .com domains.
2. The root directs it to Verisign’s .com TLD servers.
3. Then, your resolver queries those TLD servers for the authoritative name servers of example.com.

This multi-step delegation is fundamental to how DNS maintains its distributed architecture.

Why Distribution Matters

The global distribution of root server instances serves several critical purposes. It creates redundancy so that if one server instance goes offline or becomes overloaded, traffic will automatically route to the next nearest instance.

The Anycast technology behind this system ensures that queries are handled by the physically closest server, significantly reducing latency. This distributed model also provides the scalability to handle the billions of daily DNS queries on the internet without creating bottlenecks.

Some common misconceptions worth clarifying include the nature of the 13 servers – these are 13 logical names, each representing numerous physical servers worldwide.

Major operators include Verisign (managing A and J roots), ICANN (managing L roots), and other organizations, all coordinated through root-servers.org.

Note: Root servers never store actual website IP addresses; their primary function is to direct queries to the appropriate TLD servers.

In the DNS hierarchy, root servers perform the vital first step in domain name resolution, ensuring queries are started correctly. Their distributed design makes the internet infrastructure resilient against technical failures and malicious attacks.

To understand their role, imagine root servers as air traffic control; they don’t land planes (resolve final IPs) but direct flights (queries) to the correct destination airports (TLDs), with multiple control towers (server instances) ensuring uninterrupted service.

FAQS

Other Blogs of Interest

– The Future of Domain Registration: Hosted.com’s Advanced AI Domain Name Generator

– The .com Domain: Everything You Need to Know

– Free Domain Checker: Find Available Domain Names

– Domain Maps: A Guide To Creating Yours

– What Is Domain Hijacking And How Can You Prevent It