What is DNS?¶
title: "What is DNS?" card_id: "IP-035" status: "complete" source_document: "https://docs.google.com/document/d/1I-Kn7-kMQZhYXWvrwv7ldXUKsx_XVmj4lzkxDCvkfuA/edit?usp=drivesdk"
What is DNS?¶
Computers communicate across networks using IP addresses.
People, however, generally prefer names.
It is easier to remember a name such as ifdigital.co.uk than an IPv4 address such as 203.0.113.25—or a much longer IPv6 address.
The Domain Name System, usually shortened to DNS, connects those two things.
DNS is often described as the internet’s phone book.
That is a useful starting point, but DNS does more than simply hold one name and one address.
It is a distributed system containing different types of records about domain names.
Some DNS records associate a name with an IPv4 or IPv6 address. Others identify mail servers, provide aliases, show which servers are responsible for a domain or publish information used by other services.
When a device needs to contact a named service, it can ask DNS for the relevant information.
For example, if somebody enters a website name into a browser, the device needs to discover an IP address it can contact.
DNS provides an answer, and the device can then attempt to connect to that address.
DNS doesn't normally carry the webpage, email or other content itself. It helps the device find the system responsible for providing the service.
There is no single DNS database containing every answer.
Responsibility is distributed across many systems and organisations. Different servers may help find the answer, while particular servers hold the official records for a domain.
A DNS answer isn't necessarily permanent.
A domain name can move to a different IP address. It can use several addresses simultaneously, and different users may receive different answers depending on their location or the way the service is configured.
Several different domain names can also use the same IP address.
This means that a DNS result showing a connection between a domain name and an IP address doesn't prove that the relationship has always existed—or that the address belongs exclusively to that domain.
DNS also doesn't normally identify the person who registered, administered or visited a domain.
It describes technical information used to locate and operate internet services.
A DNS query may form part of the process of accessing a service, but a DNS record alone doesn't prove that somebody visited a website or completed any particular activity.
DNS gives names a practical meaning on a network. It allows devices to find services without people having to remember and enter their IP addresses directly.