The Domain Name System connects the names of websites to their underlying IP addresses, increasing efficiency and even security.
The Domain Name System (DNS) is one of the internet’s pillars, working in the background to match web site names entered into search boxes with the corresponding IP address, a long string of numbers that no one can be expected to remember.
It is still possible to access a website by typing an IP address into a browser, but most people prefer an internet address to be made up of easy-to-remember words known as domain names. (For instance, Network World.)
When your computer wants to find the IP address associated with a domain name, it first uses a DNS client, which is usually a Web browser. After that, the query is routed to a recursive DNS server, also known as a recursive resolver. A recursive resolver is typically operated by an Internet Service Provider (ISP) such as AT&T or Verizon (or another third-party), and it knows which other DNS servers to query in order to resolve a site’s name with its IP address. The authoritative name servers are the servers that actually have the required information.
DNS is structured in a hierarchical manner. A recursive resolver is queried for the first time for an IP address. This query first takes you to a root server, which contains information on top-level domains (.com,.net,.org) as well as country domains. Because root servers are located all over the world, the DNS system routes requests to the closest one.
When a request reaches the correct root server, it is routed to a top-level domain server (TLD nameserver), which stores information for the second-level domain, which is the words entered into a search box. The request is then routed to a domain nameserver, which looks up the IP address and returns it to the DNS client device, allowing it to access the appropriate website. All of this happens in milliseconds.
What is DNS caching?
You probably use Google several times per day. Instead of your computer querying the DNS nameserver for the IP address each time you enter the domain name, that information is saved on your personal device, so it does not need to access a DNS server to resolve the name with the IP address.
Additional caching can occur on routers that connect clients to the internet, as well as on the user’s ISP’s servers. Because there is so much caching going on, the number of queries that actually make it to the DNS name servers is significantly reduced, which improves system speed and efficiency.
