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What happens when you want to open a website in your browser? It would seem simple. Just enter its address in the browser line - and in a few seconds the content of the requested page will appear in front of you. The Domain Name System (DNS) is responsible for making everything work exactly like this , which we use every day, even if we don’t know about it. In today's article, we will analyze why DNS is needed, what principles and algorithms it works on, and what you need to know about this system if you are going to place your website on the World Wide Web.
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What is a DNS server and what role does it play in the life of any Internet user
Any web resource on the Internet physically “lies” on some device. For example, on the server of wordpress web design agency a hosting provider or even your personal home machine. This device has its own identifier — IP address , which consists of four numbers separated by a period in the range from 0 to 255. Using the IP address, you can figure out where exactly the site or web application is loaded from.
The DNS algorithm is easiest to explain using a telephone directory as an example.
Think of the IP address of the server where the website is stored as a phone number, and DNS as a book with all the “numbers”.
When you enter the address ( domain name ) of the site you want to visit into the address bar of your browser, DNS finds the corresponding IP address and gives it to the browser. The web server then processes the client's request and sends the content of the desired web page.
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The DNS structure resembles a logical tree. The domain name space has a certain hierarchy. At the very top is the root domain. From it, the first-level domains "branch off", then the second, and so on.
DNS server: and the algorithm of work
The key element of the DNS system, as you might guess, is the DNS server. It performs two tasks:
stores data about which IP addresses correspond to domain names;
caches resource records of other DNS servers.
Let's say that you visit a web resource every day that is physically located outside the country. Constantly sending requests to the primary server would take a lot of time, and you as a user would have to wait for the pages to load. However, in reality, it works differently. The DNS server closest to you caches data on previously requested IP addresses and immediately returns them upon subsequent access.
Let's take a closer look at the DNS server's operating algorithm:
An Internet user types the domain name of the site he wants to visit in the browser's address bar. The browser sends it to the DNS server, which looks for the IP address corresponding to this domain. If a match is found, the web page opens in the browser. But if a match is found, the request is sent to a higher-level server or the root DNS server.
The root DNS server sends a request to the first-level server, which sends a request to the second-level server, and so on down the chain until the system finds an IP address that matches the domain name entered by the user.
The browser receives an IP address, contacts the web server, and the page content is downloaded from the hosting.
In some cases, the opposite situation is also possible - when the DNS is searched for not an IP address, but a domain name. This is relevant for email servers.
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