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What is DNS? A beginner’s guide to Domain Name Systems

The domain name system assigns types of IP address to a domain name, and is a fundamental building block of online communications. DNS effectively acts like an address book for the internet. Here’s how the domain name system works.

Charles Whitmore

Charles Whitmore

What is DNS? A beginner’s guide to Domain Name Systems

History of the domain name system

During the early days of the internet, assigning an IP address to a domain name wasn’t automated — it was in the hands of Elizabeth Feinler, a computer scientist at Stanford Research Institute. Before the internet had become a widespread phenomenon, manually keeping track of which domain names and IP addresses were linked was a much slower process.

As the internet grew and more domains were needed, Feinler’s manual recording of IP addresses and domain names weren’t feasible. The internet’s growing popularity meant a more robust method was needed.

In 1983, another computer scientist called Paul Mockapetris developed a dynamic system that automatically linked IP addresses with domain names without the need of a manually created reference table. This revolutionary new system was DNS. While you can still manually type in IP address information into your address bar, it’s much easier and simpler to type in a short domain name. Mockapetris made all DNS information freely available.

DNS basics – how does DNS work?

What is DNS to the internet as a whole? It’s a vital communication system. The basics of online communication require the knowledge of what IP address to follow for the desired user outcome. Luckily, instead of having to type a string of letters into your URL bar, you only need to type in the domain name of a website, like Google.com.

Once you type in a domain name into your URL bar and click “search”, the browser sends a query to whichever server holds the correct data. Once it obtains the IP address, your browser finally has all the information it needs to lead you to your desired website.

A DNS query that’s sent to a server will automatically translate IP addresses into domain names, instead of the user having to manually enter an IP address themselves.

What is a DNS lookup?

A DNS lookup is the process of searching a domain name with the intent of retrieving an IP address from the correct DNS servers. When a server receives a DNS query from a browser, it’s known as a DNS lookup.

There are ways to manually check the availability of domain names, along with whichever IP addresses are directly linked to specific domain names. A giant tech corporation like Google would have several different root servers and may use multiple different types of domain name. By using a website like whois.com, you can manually cross reference domain names and IP addresses.

When you enter a domain name into your URL and click “search”, the lookup process is automatically handled via DNS. DNS queries go through multiple servers to retrieve the correct IP address.

Here’s a step by step process of how DNS lookup works:

    1. A domain name is entered into a browser’s URL bar.
    2. Once prompted, the browser sends a message to the network to query which network or IP address the domain name belongs to.
    3. The query is received by a DNS resolver, or DNS recursor. If the recursive server doesn’t have the necessary IP data stored in a DNS cache, it will send forth more queries to other servers.
    4. Root nameservers and TLD nameservers will receive the queries, and work in tandem to narrow down where to find the correct IP address details.
    5. The final data point is the authoritative nameserver, where the exact domain-IP details can be found.
    6. The information is relayed back to the recursive resolver, which gives the browser the correct IP address to visit. The DNS resolver will cache DNS records for easier access next time the user wants to visit the website in question.

While it sounds like working through four different servers would be time consuming, DNS lookup happens instantly.

Where is the information stored?

As of late 2021, people have registered 341.7 million domain names. All the system information that connects IP addresses to domain names is stored in database servers. As a browser makes IP address DNS queries, it has to travel through four different DNS servers until the desired DNS record is found. A DNS server can refer to any of the following:

    1. DNS recursor. A recursive server, often known as a DNS resolver or recursive resolver, receives the IP address query. It was created with the purpose of collecting user queries via browsers. Once it receives the recursive query, it can make further requests with other DNS servers to resolve it. The recursive server is the first step in the DNS infrastructure.
    2. Root nameserver. A DNS resolver will send a query to a root nameserver. A root nameserver helps translate an alphabet domain name into a numerical IP address. This DNS server helps narrow down where the requested IP address can be found and helps specify the correct location. Why not go to the root server first? Root servers can’t handle the sheer number of requests or DNS queries, the DNS resolvers help keep things organized.
    3. TLD nameserver. TLD stands for a top-level domain server. In the context of a library, rather than being the section of books that the nameserver led you to, the TLD nameserver brings you to the specific shelf in the already identified section.
    4. Authoritative nameserver. An authoritative nameserver is the fourth and final server in the DNS query process and contains the desired domain name with the corresponding IP address. As the IP address is identified, the information relays back to the recursive resolver, which in turn will send the results back to the user’s browser.

Key differences between Authoritative DNS servers and Recursive DNS servers

A recursive DNS server was created to react and respond to DNS queries and is able to track down the correct records needed to find the correct root nameserver. Sometimes, recursive DNS servers will need to create multiple requests until the nameserver is found. A recursive server will only be able to respond to queries by finding the results from other DNS servers.

Authoritative DNS servers are always the final data point in the IP address retrieval process — it’s the last segment of the DNS server chain. When an authoritative DNS server receives a query, it doesn’t need to communicate with any other servers. The authoritative server already has the data needed to answer the DNS query. A recursive query, on the other hand, will always rely on other servers for the desired data.

IP Addresses and DNS Servers

IP addresses and DNS servers live together in a symbiotic and necessary relationship. Without DNS records, you would need to find and keep note of all IP addresses for your most visited websites. Domain name servers create convenience for everyone using web browsers.

Just think of DNS records as your online address book. You already have the (domain) name of the person (website) you want to talk to – now you just need the phone number (IP address) to start communication.

DNS servers help pair domain names with IP addresses. While most domain names will have a unique IP address, there are some domains that have multiple addresses. Giant corporations like Apple or Amazon will have potentially thousands of servers around the world, each with a specific IP address. DNS data ensures that the domain name will always connect to the best local DNS server.

DNS Caching

Most browsers and operating systems will indulge in DNS caching, a method that helps keep online performance at peak efficiency. A cache is a small store of data that is used to keep loading times to a minimum. The DNS lookup process can be shortened via DNS caching. When it comes to caching for a DNS server, the recursor server stores the cached information.

If a browser has a DNS cache, instead of having to communicate with DNS servers to retrieve an IP address, the cache can directly find the correct identifying records. Loading speeds can be kept as short as possible by retrieving the necessary data from a local cache. A cache of data isn’t limited by OS or browser, with a user’s internet service provider often providing its own recursive resolver cache to keep bandwidth at reasonable levels.

NordVPN DNS servers can be automatically configured to your devices, as a means to prevent any potential DNS leaks. Beware, however, of DNS cache poisoning. This is where a hacker will feed incorrect cache data into your DNS cache, with the intent to lead you to a malware-ridden website, or to a site that will harvest incriminating information.

DNS FAQ

Here are some common queries when it comes to the domain name system.

What’s the difference between top-level domains and second-level domains?

Top-level domains are the third stop in regards to DNS lookups, and they specifically refer to the final part of a domain name. Second-level domains refer to the main ‘flavor’ text of a domain name. Let’s look at Google.com as an example. “.com” would count as the top-level domain, and the main search criteria when the DNS lookup process reaches the TLD server. “Google” counts as the second-level domain. A DNS resolver will look specifically for correct TLDs in order to match the desired domain name.

Does it matter what TLD a website uses?

Other than to designate or target a specific audience, the use of different TLDs won’t affect a website’s ranking on Google. Obviously, someone from the UK will want to find a “.co.uk” version of a website to use rather than a “.com” version, especially in regards to online shopping and shipping fees.

However, when it comes to general search engine rankings, Google clarified in 2015 that it doesn’t matter if a site has “.net” or “.com”, it will still treat all domain names the same.

What is ICANN?

ICANN, the Internet Corporation for Assigned Names and Numbers, oversees and manages the allocation of IP addresses to domain names. ICANN is a non-profit organization that works to ensure the domain name system continues to function correctly. DNS data is directly regulated by ICANN.

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Charles Whitmore
Charles Whitmore Charles Whitmore
لدى Charles ككاتب محتوى شغف بالخصوصية عبر الإنترنت وحرية المعرفة. ولأنه تقني لديه نقطة ضعف للتكامل الكامل للمنزل الذكي – فهو يعتقد أنه يجب على الجميع السعي جاهدين لمواكبة تحديثهم عبر الإنترنت.