What is DNS?

Summary: DNS stands for Domain Name System. It is often referred to as the "phonebook of the internet" because it is essentially a directory that matches domain names with IP addresses.

The internet as we know it today would not be possible without DNS – the Domain Name System that translates domain names like example.com into IP addresses that computers use to route traffic. When you type a web address into your browser, DNS is the technology that helps get you to the right place.

DNS has been a fundamental building block of the internet since the 1980s, but it remains a bit of a mystery to most casual web users. Read on for a comprehensive overview of what DNS is, how it works, and why it’s essential for navigating online.

An Introduction to DNS

DNS stands for Domain Name System. It is often referred to as the “phonebook of the internet” because it is essentially a directory that matches domain names with IP addresses.

Humans access information online through domain names, like nytimes.com or espn.com. Web browsers interact through Internet Protocol (IP) addresses – those strings of numbers separated by periods that look something like 50.18.199.26. DNS translates domain names to IP addresses so that browsers can load internet resources.

Each device connected to the internet has a unique IP address which other machines use to find the device. DNS servers eliminate the need for humans to memorize IP addresses like 192.168.1.1 (in IPv4) or more complex newer alphanumeric IP addresses like 2400:cb00:2048:1::c629:d7a2 (in IPv6).

So in summary, DNS is like an address book that matches the domain name you type into your browser (the name) to the numerical IP address (the address) that computers use to properly route information over the internet.

The Origins of DNS

The domain name system traces back to 1983 when a computer scientist named Paul Mockapetris proposed the idea as part of his PhD dissertation at the University of Southern California. His concept outlined the distributed database system that became the Domain Name System still in use today.

In 1984, the first testbed for DNS was developed. By 1987, a team led by Mockapetris created the current DNS architecture and software that became the standard for the modern internet. DNS was adopted as the naming system for the fledgling internet around 1989.

Since then, DNS has continued to evolve to keep pace with the exponentially growing demands of internet. By the 1990s, the rapid expansion of the World Wide Web placed increasing loads on the relatively simple DNS system which led to the development of more robust, scalable DNS architecture.

Today, Cloudflare operates one of the largest DNS networks in the world, processing over 20 billion DNS queries per day. We also host authoritative DNS servers for more than 2 million Internet properties including major sites like Shopify and Peloton. The DNS infrastructure now spans globally to reliably handle trillions of requests and keep internet traffic flowing smoothly.

How Does DNS Work?

Now that we’ve covered a brief history of DNS, let’s look at how it actually works. The process of DNS resolution involves converting a domain name (www.example.com) into a computer-friendly IP address (192.168.1.1).

Domain names are designed to be memorable and easy for humans to recognize and remember. But computers access the internet through numerical IP addresses assigned to each device. DNS serves as the bridge between these two identification systems.

When you type a domain name into your browser and hit enter, a DNS lookup takes place. Your browser will first check its local cache to see if it already has the corresponding IP address handy. If not, it will query the DNS resolver provided by your Internet Service Provider (ISP).

The DNS resolver is like a librarian who goes to hunt down the answer from the global DNS records. It will contact each lower level of DNS servers until it reaches the authoritative name server for the domain name requested.

The authoritative name server is like a dictionary that matches the domain name in the query to the correct IP address. Once located, the IP address gets communicated back to the browser that initiated the lookup so it can now finish loading the requested webpage.

Behind the scenes, four types of DNS servers work together to make the DNS lookup happen quickly and seamlessly:

• DNS recursor – The recursor receives queries from client machines through apps like web browsers. It handles additional requests needed to satisfy the query.
• Root nameserver – The starting point for translating human readable host names into IP addresses. Points requests to the proper TLD nameserver.
• TLD nameserver – The top level domain server stores the last portion of a domain name (like .com) and points to the domain’s authoritative nameserver.
• Authoritative nameserver – The final stop and source of truth for the requested DNS record. Responds with the IP address associated with the queried domain name.
• This hierarchy of DNS servers around the world keeps the address lookup process short and efficient for billions of queries made per day.

There are also two important types of queries that take place during DNS resolution:

• Recursive query – The DNS client requires the DNS resolver to respond with the requested record or an error if it can’t be located.
• Iterative query – The client allows the DNS server to return the best answer it has available. The resolver may have to contact multiple authoritative name servers to get the fully resolved IP address.

Now that we’ve outlined the basic roles of DNS servers and process of DNS queries, let’s take a closer look at what happens during a typical DNS lookup.

The 8 Steps in a DNS Lookup

When you type a domain name (let’s say example.com) into your browser, it goes through the following steps to translate the name into an IP address:

1. Local DNS resolver gets the request and queries a root nameserver (“).
2. The root server responds with the address of the Top Level Domain (TLD) nameserver (.com).
3. The TLD nameserver for .com is queried.
4. The TLD server returns the IP address of the domain’s authoritative nameserver (example.com).
5. The authoritative nameserver for example.com is queried.
6. The IP address of example.com is returned.
7. Local DNS resolver replies to browser with the IP address.
8. Browser can now complete the request using the IP address.

Once the IP address is acquired, the browser can fetch the webpage. The whole process typically takes just milliseconds to complete.

It may seem complex, but DNS lookups happen automatically every time you access a website or web-based service. The distributed hierarchy of DNS servers around the globe streamline this critical process for billions of daily queries.

Note that DNS information is cached at multiple levels during this process to reduce delays and bandwidth usage. Your browser and OS have a cache to check before querying external DNS servers. The DNS resolvers provided by your ISP also maintain caches containing common DNS records.

As long as the cached data hasn’t expired yet, DNS lookups can skip querying certain nameservers to speed up the IP retrieval. Caching helps the DNS infrastructure quickly handle the staggering number of requests without crumbling under the load.

The Key Difference Between DNS Servers

There are two main types of DNS servers that operate behind the scenes to make DNS work: recursive resolvers and authoritative nameservers.

A recursive resolver handles the user’s DNS query and does the legwork of tracking down the answer from DNS data sources. Many ISPs maintain clusters of high performance recursive resolvers to quickly handle all the queries originating from their customer’s devices.

An authoritative nameserver is a DNS server that actually stores DNS records instead of caching them temporarily. This includes critical infrastructure servers like the root servers and TLD registries which form the backbone of the DNS system. They respond to queries with verified DNS data from their own authoritative records.

The Importance of DNS

Now that you understand the basic inner workings of DNS, let’s quickly cover why it’s such a crucial component of internet infrastructure. Here are some key reasons DNS is essential:

• Allows human friendly domain names to be translated for computers
• Decentralized structure scales easily without single point of failure
• Hierarchical framework optimizes lookups and reduces traffic
• Caching minimizes delays for popular queries and heavily trafficked domains
• High performance anycast networks prevent outages and geo-locate responses
• Supports reliability and redundancy in addressing

While it may not be a topic that most internet users think about often, DNS is fundamental to delivering the seamless online experience that people around the world depend on. The next time you visit your favorite website, remember that DNS played a role in getting you there!

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