What is DNS?
DNS stands for Domain Name System, a hierarchical naming system used for identifying computers, services, or other resources on the internet or private networks. DNS associates domain names with essential information, most importantly, their corresponding IP addresses. These IP addresses are essential for locating computers and services within a network. By translating numerical IP addresses into easy-to-remember alphanumeric domain names, DNS plays a vital role in the functionality of the internet. It functions like a phonebook, linking IP addresses to easy-to-remember domain names, much like phone numbers are matched to people’s names.
How DNS Works
DNS translates domain names into IP addresses. For example, the domain www.example.com, a demonstration domain created by the IETF (Internet Engineering Task Force), is resolved by DNS to the IPv4 address 192.0.43.10 and the IPv6 address 2001:500:88:200::10. IPv4 is the fourth generation of IP addresses, widely used today, while IPv6 was introduced to address the depletion of available IPv4 addresses. DNS allows these updates to occur seamlessly, meaning the locations of computers and services can change without affecting users.
DNS operates as a client-server database, where the individual nodes are known as name servers. Every domain has at least one DNS server that provides information about the domain and its associated name servers. At the top of the DNS hierarchy are root name servers, which are responsible for resolving top-level domains (TLDs) such as .uk, .com, .net, and others. Name servers are classified as either master servers or slave servers. Master servers store all the original data about the domains, while slave servers always contain exact copies of the master servers through an automatic update mechanism.
When a new domain is registered, it must be linked to at least one primary server (usually a master server) and one secondary server (typically a slave server). This ensures that the domain remains accessible even if one server goes down. When you attempt to open a website, name servers perform a series of queries to narrow down the possible domains until they locate the correct one. DNS tracking tools are available, allowing you to trace network information, such as finding an IP address or tracking the route between your computer and the web server hosting the site.
Example of DNS in Action
Let’s say you’re looking for the domain www.example.uk:
- 123.45.6.7: the root name server finds the TLD (.uk) and sends a possible IP address to the next name server
- 123.45.678.9: this name server narrows the search based on the second-level domain (SLD), and if necessary, sends it to another server
- 123.456.789.123: finally, the name server finds the exact IP address, allowing your browser to load the website
To speed up searches, internet service providers (ISPs) use caching, storing previously resolved domain name-to-IP address pairs for faster lookups.