What is DNS and how does it work?

When your computer wants to find the IP address associated with a domain name, it first makes its DNS query via a DNS client, typically in a Web browser. The query then goes to a recursive DNS server, also known as a recursive resolver. A recursive resolver is typically operated by an Internet Service Providers (ISP), such as AT&T or Verizon (or some other third-party), and it knows which other DNS servers it needs to ask to resolve the name of a site with its IP address. The servers that actually have the needed information are called authoritative name servers.

DNS is organized in a hierarchy. An initial DNS query for an IP address is made to a recursive resolver. This search first leads to a root server, which has information on top-level domains (.com, .net, .org), as well as country domains. Root servers are located all around the world, so the DNS system routes the request to the closest one.

Once the request reaches the correct root server, it goes to a top-level domain server (TLD nameserver), which stores information for the second-level domain, which is the words that you type into a search box. The request then goes to a domain nameserver, which looks up the IP address and sends it back to the DNS client device so it can visit the appropriate website. All of this takes mere milliseconds.

What is DNS caching?

Chances are that you use Google several times a day. Instead of your computer querying the DNS nameserver for the IP address every time you enter the domain name, that information is saved on your personal device so that it doesn’t have to access a DNS server to resolve the name with the IP address.

Additional caching can occur on the routers used to connect clients to the internet, as well as on the servers of the user’s ISP. With so much caching going on, the number of queries that actually make it to the DNS name servers is significantly reduced, which helps with the speed and efficiency of the system.

How does the DNS numbering system work?

Every device that connects to the internet needs to have a unique IP address in order to have traffic properly routed to it. DNS translates human queries into numbers using a system known as IPv4 or IPv6. With IPv4, the numbers are 32-bit integers that are expressed in decimal notation.