What is DNS in simple terms
Any website on the internet actually resides on some device. An individual computer connected to the internet has an individual number called an IP address. This is a set of four numbers from 0 to 255. The address allows you to find out where the page you are looking for is being downloaded from.
The IP address of a device can be compared to a mobile phone number and DNS to a phone book (we borrowed this analogy from The Complete Guide to Web Hosting and Servers review). More specifically, DNS is a system of domain names that references a site's name to its numeric address.
In other words, a user types a resource's domain name into a web browser and DNS translates the name into an IP address and transmits it to your device. The computer at that address processes the request and sends the information to open the desired page on the site.
The structure of the DNS can be thought of as a logical tree. The system contains a distributed database of domain names, a space that is organized hierarchically. The top level is the root domain and the first level domains are placed next to it. To each of them join the second level domains, and so on.
What is a DNS server
The domain name system operates through the DNS-server, which is needed to perform two main functions:
- storing data on the correspondence of a domain name to a specific IP address,
- caching of resource records of other DNS-servers.
If the user intends to visit a site located in another country, the regular transfer of requests to the primary server takes a lot of time and leads to slow loading of pages. To avoid such inconveniences, the DNS server located near your device caches data about the previously requested IP addresses and issues them the next time they are requested.
The source of the resource records are the source DNS servers that contain the initial links between domains and host network addresses.
As a rule, it is recommended to use two servers: primary and secondary. This ensures that your domain can be accessed, because if one server is unavailable, the other will respond.
How DNS servers work
Let's consider step-by-step the operation of applications designed to respond to DNS queries:
- The browser receives a request from the user and sends it to the network's DNS server, which looks for a match between the domain name and the network address. If the response is detected, the website page loads immediately. Otherwise, the request is sent to a higher-level server, or root server.
- The root server forwards the request to the first-level server, which in turn forwards it to the second-level server. This movement continues until a name and IP address match is found.
- The browser receives an answer to its request, forwards it to the host, and the page opens.
It is also possible to reverse the procedure – search for the domain name in the DNS server that matches the requested IP address. For example, this happens in the case of an email server.
Where DNS-servers are located
Foundation for the processing of requests for domain names are the root servers responsible for the root DNS-zone. They are managed by different operators, who ensure the smooth functioning of the servers. The first root servers appeared in North America, but over time they began to appear in other countries around the world. Today, there are 123 root servers located around the world (depending on the intensity of use of the World Wide Web).
Why do you need to assign DNS servers?
Imagine that you just registered a domain. To make information on the existence of your domain available to other servers, you must specify resource records. The first thing you must do is to configure and assign DNS servers for the domain.
Servers in this format are updated up to 24 hours, during this period, the site may not work. Therefore, you must wait a day after you prescribe them.
Often these servers are prescribed in pairs. Each domain has one primary and up to 12 secondary servers. This is to ensure the reliability of the site. If one of them goes down, the domain and resource will still function.