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This is an introduction to basic DNS concepts to help new users understand DNSFilter's capabilities. 

What is DNS?

Domain Name System (DNS) is a system for computers and services connected to the Internet that resolves domain names to IP addresses. It converts human-readable domain names (www.dnsfilter.com) into Internet Protocol (IP) addresses (184.73.183.75).

This is because computers can only communicate using a series of numbers, so DNS was developed as a sort of “phonebook” that translates the domain you enter in your browser into a computer-readable IP.

How does DNS Work?

We already know that DNS maps IP addresses to domain names, but where is this information stored? These are stored on something called nameservers.

Nameservers store DNS records which is the actual file that says “this domain” maps to “this IP address.” This being said it is not as simple as there being one room that has all the nameservers and DNS records in one spot. Instead, it is distributed all over the world and stored in something called root servers. Instead of these root servers storing every domain name ever, they store the locations of the Top Level Domains (TLDs) where these domain names are located.

These TLDs would be two or three-character extensions like ".com," ".org," or for different countries like ".ca." Each TLD has its own set of nameservers that store the information of who is authoritative for storing the DNS records for that domain.

Authoritative DNS Servers

The authoritative nameserver is typically the DNS provider or the DNS registrar (like GoDaddy, which offers both DNS registration and hosting). This is where we can find the DNS record that maps example.com to the IP address 127.66.122.88.

An Authoritative DNS server holds the information for the domain (e.g. dnsfilter.com) it serves. This information is contained in an A record, or CNAME record if the domain has an alias.

Authoritative DNS servers are not always part of a DNS query because the information they provide is sometimes cached by recursive DNS servers and DNS clients the first time it is received.

If a user attempts to access a domain they already have, and the authoritative DNS information is cached, the query will resolve without contacting the Authoritative nameserver.

An authoritative nameserver is the last point of call in a DNS query operation when the DNS client makes a (does not go through its cache) fresh request for the domain’s IP address.

A DNS query goes through a tree-like path from root servers through recursive servers to finally find the information for the domain on the server that is authoritative for that domain.

What Protocol Layer does DNS operate on?

DNS is such an important protocol, and the internet would not be so usable today without it. 

DNS is an Application-layer protocol. The Application layer is the top-most layer on the TCP/IP Model. Just like every application layer protocol, DNS uses the User Datagram Protocol (UDP) on the Transport layer of the TCP/IP model to transport data.

UDP is preferred over TCP for DNS because of its speed and lightweight packets. Read more about other security protocols like DoT and DoH in our related article.

The DNS layer provides networking support to identify and locate computer services and devices with the corresponding protocols. Simply put, when a client application requests that a domain name be converted into an IP address, the task is completed within the application layer by DNS.