How Domain Name Servers (DNS) Function

The internet and the World Wide Web are vast realms powered by computer languages, codes, and web browsers, all designed to find and exchange data. One of the cornerstones of the internet is the Domain Name System, or DNS. (Though many people mistakenly believe "DNS" means "Domain Name Server," it actually stands for "Domain Name System.")

DNS operates as a protocol within the broader set of standards used for data exchange across the internet and private networks, referred to as the TCP/IP protocol suite. Its function is essential, as it translates user-friendly domain names like "Mytour.com" into Internet Protocol (IP) addresses, such as 70.42.251.42, which computers use to recognize one another on the network. In essence, it serves as a system that pairs names with numbers.

Think of the DNS system as the internet's version of a phone book. Without such a directory, you'd be left to navigate the vast, complex web of data scattered across the globe in much more convoluted ways... and trust me, it wouldn't be nearly as enjoyable, especially with the hundreds of millions of domain names in play [source: VeriSign].

Without DNS servers, the internet would quickly grind to a halt. But how does your device know which DNS server to use? Typically, when you connect to your home network, ISP, or WiFi, the modem or router that assigns your device's network address also provides crucial network settings, including one or more DNS servers for your device to use when translating DNS names to IP addresses.

You've already learned some essential DNS fundamentals. The remainder of this article explores domain name servers and the process of name resolution in more detail. It even introduces how you can manage your own DNS server. Let's start by examining how IP addresses are structured and why this structure is vital to name resolution.

DNS Servers and IP Addresses

You've just discovered that the primary function of a DNS server is to resolve (or translate) domain names into IP addresses. While this may seem like a straightforward task, it becomes more complex due to several factors:

Given the sheer volume of data to manage, DNS servers rely heavily on network efficiency and internet protocols. Part of the power of the IP system is that each machine on a network has its own unique IP address, whether under the IPV4 or IPV6 standards, both overseen by the Internet Assigned Numbers Authority (IANA). Here are a few ways to identify an IP address:

Web servers and other systems that require a constant point of contact use static IP addresses. This means that the same IP address is consistently assigned to the system's network interface whenever it connects to the internet. To ensure this, the IP address is linked to the Media Access Control (MAC) address of that interface. Each network interface, whether wired or wireless, has a unique MAC address set by the manufacturer.

Now, let's turn our attention to the other side of the DNS equation: domain names.

Domain Names

If we had to memorize the IP addresses of all our favorite websites, it would be a nightmare! Humans aren't great at recalling long strings of numbers. However, we're quite skilled at remembering words, which is where domain names come into play. You likely have hundreds of domain names stored in your mind, such as:

Domain names typically consist of strings of characters separated by dots (periods). The final segment in a domain name corresponds to the top-level domain. These top-level domains are managed by the IANA within the Root Zone Database, which we’ll explore in more detail later [source: IANA]. There are over 1,000 top-level domains, and here are some of the most familiar:

In a domain name, every word and dot combination you add before the top-level domain represents a level in the domain hierarchy. Each level refers to a specific server or a set of servers responsible for managing that domain. For example, "Mytour" in the domain name is a second-level domain within the COM top-level domain.

An organization may have a hierarchy of sub-domains to better structure its online presence. For instance, "bbc.co.uk" is the BBC's domain under the CO second-level domain, a level created by the domain authority that oversees the U.K.'s country code.

The first part of a domain name, like www or mail, is referred to as the host name. This designates a particular machine (with a unique IP address) within the domain, often assigned a specific function. A domain can house millions of distinct host names, provided each one is unique to that domain.

The 'http' stands for Hypertext Transfer Protocol, which is the method used to send information from a user to the website they are accessing. Today, however, you're more likely to encounter 'https,' which indicates a secure version of the protocol, ensuring the data sent is encrypted. This is especially crucial when entering sensitive information like a credit card number on a website [source: EasyNews].

When we discuss how to create a domain name later, one of the steps involves selecting one or more name servers (DNS servers) that hold the authority to resolve the host names and sub-domains within that domain. This process is typically done through a hosting provider, which operates its own DNS servers. Up next, we’ll explore how these DNS servers manage your domain and how DNS servers across the internet collaborate to ensure proper traffic routing between IP addresses.

The Distributed System

Every domain is associated with a domain name server (DNS) that handles its requests. A dedicated person or IT team manages the records stored in that server's database. No other database on Earth handles as many requests as DNS servers, as they manage queries and updates from millions of users daily. What makes DNS truly remarkable is its distributed nature — it's spread across millions of machines, operated by millions of people, but still functions as if it's a single, unified database!

Managing DNS can seem like an overwhelming task, which is why many leave it to IT professionals. However, by understanding the basics of how DNS functions and how servers are distributed throughout the internet, you can confidently manage DNS on your own. The first step is understanding the role of the DNS server within the network it belongs to. A DNS server will typically have one of these two primary functions:

DNS servers that handle the first task are typically operated by your internet service provider (ISP). As mentioned previously, the ISP’s DNS server is part of your network configuration, provided by DHCP when you connect to the internet. These servers are housed in your ISP's data centers, and they process requests in the following manner:

The second type of DNS server, typically linked to web, mail, and other hosting services, is easier for non-technical users to manage, though some advanced IT professionals still set up their own DNS servers. Hosting services have simplified DNS management for everyday users.

A DNS server that manages a particular domain is known as the Start of Authority (SOA) for that domain. The information from the SOA regarding host lookups gradually propagates to other DNS servers, which then propagate it further across the internet.

The vast network of DNS servers includes the root name servers, which are positioned at the top of the domain hierarchy for each top-level domain. For every top-level domain, there are hundreds of root name servers available. Although DNS lookups don't always begin with a root name server, it can be contacted as a last resort to help locate the Start of Authority (SOA) for a domain.

Now that you understand how DNS servers are interlinked to streamline the process of name resolution, let's explore how you can configure a DNS server to be the authoritative server for your domain.

Creating a New Domain Name

To create a new domain name, follow these steps:

Whether your SOA is hosted elsewhere or on your system, you can adjust your DNS settings to add sub-domains, redirect emails, and manage other services. This data is stored in a zone file on the DNS server. If you're running your own server, you’ll likely need to manually update the zone file using a text editor. Many registrars now offer web interfaces for DNS management. Each modification you make is referred to as a record, and here are the most common record types you can configure for your DNS server [source: GoDaddy.com].

Here’s an example of how a zone file might appear if you’re editing it directly in a text editor. Note that the second column (middle item on each line) specifies the record type, such as those listed above. When you see an "@" in the first column, it means the record applies universally unless otherwise noted:

@ NS primary-auth-server.Mytour.com

@ NS secondary-auth-server.Mytour.com

@ MX priority 10 email-service

mail A record 209.170.137.42

vip1 A record 216.183.103.150

www CNAME vip1-server

For most users, MX and CNAME records will be the most practical. MX records allow you to direct your email services to another provider, such as Google Apps, instead of using your web host's default service. CNAME records, on the other hand, allow you to assign host names within your domain to other locations. For example, you can make google.example.com redirect to google.com, or direct traffic for a gaming server to a dedicated IP address like gameserver.example.com.

The Ever-Evolving DNS

DNS is always changing. In late 2018, ICANN introduced new security features for DNS, particularly modifying the cryptographic keys used in DNSSEC (Domain Name System Security Extensions). Known as the root zone key signing key (KSK), this update was essential to enhance security, especially considering the rapid growth of the Internet of Things (IoT) and its millions of new connected devices [source: Cooney].

These security updates are crucial because hackers often target DNS to steal data or cause disruptions, such as with DNS hijacking. Both security-conscious users and IT experts must remain informed about preventive strategies to defend against DNS poisoning, denial-of-service attacks, and similar threats [sources: Greenberg].