What is a DNS And What is Important to Know About it? (Part 1)
As the sunny and joyful mood has spread around our team in May, we – the technical support team, would like to present to your attention the next topic from the „Tips from the support” series. 🙂 In the previous articles we have been giving you many tips and guidelines on how to build more successful online presence; how to set up your hosting accounts and data bases; how to optimize the resources you are using and, of course, how to enhance your website security… But now, in this article, we are going to broaden your horizons and talk about something different, which is a basic segment of the Internet nowadays, but it is still quite vague for most of the ordinary users – DNS.
Almost every user, who has registered and is using a domain has faced the term DNS, right?
DNS stands for Domain Name System by which domains on the Internet are translated into IP addresses.
The system is designed to facilitate the users in remembering and entering names. It is much easier to write down and remember “www.superhosting.bg” instead of “18.104.22.168”.
The DNS system first appeared in 1984 when four UC Berkeley students wrote the first UNIX implementation. It is called The Berkeley Internet Name Domain – BIND. Nowadays BIND is still the most widely used DNS server.
There are two types of DNS servers: Authoritative Name Servers – servers responsible for the queries for a DNS zone and Cache Name Servers – which are responsible for all user queries while implementing the translation between a name and an IP address.
In order to explain the way a DNS records query for a domain is mapped, we first have to clarify the domains structure.
The domain name consists of hierarchical series of character strings separated by dots. (For example: superhosting.bg). The root domain stays at the top of the domain structure:
The Root domain does not have an official name and most of the time is represented as a silent dot (‘.’). Every registered domain can be loaded in a browser, as you leave a space or dot after it. For example: superhosting.bg[space] or superhosting.bg..
The contemporary DNS servers process queries without the need to put an enter or a dot after the domain name. However, you can try that right now. The websites are instantly loaded, are not they? 🙂
DNS root zone is basically the heart of the DNS system and the domains. All DNS queries go through the DNS servers at least once for a given time slot.
There are 13 authoritative root servers that are serving the root DNS zone. They keep the information for the rest of the authoritative DNS servers, which are responsible for all Top Level Domains. To this day there are 317 TLDs, added to the DNS servers. This includes gTLDs (.com, .net, .org, .info, .biz, etc. ) and ccTLDs (.bg, .uk, .me, etc. ).
The names of the Root servers are set up with letters ranging from а to m:
It is important to mention that there are not only 13 physical servers around the world, but many more. By the time we wrote this article, the total number was 365. Here comes the use of Anycast so that the network load can be regionally distributed. Anycast is a networking technique where the same IP prefix is advertised from multiple locations. In this way there could be numerous physical servers or clusters located everywhere around the world behind every IP.
9 of the root DNS servers are operating in Anycast. 10 physical servers are located in the USA as some of them operate in Anycast. 3 of the servers are in Stockholm as they are named i.root-servers.net. Another 3 are located in Amsterdam (k.root-servers.net) and the last 3 are in Tokyo (m.root-servers.net). A full map of all physical servers around the world is available at root-servers.org.
In other words, the browser needs to receive the domain IP address so that www.superhosting.bg, can be loaded. A query is made and it goes the following way:
1. The browser asks the root DNS servers what the IP address of www.superhosting.bg is. They answer that the .bg domain authoritative DNS servers can provide information.
2. Then a query is sent to the .bg domain authoritative DNS servers. They answer that the IP address not be provided by the superhosting.bg authoritative DNS servers.
3. The next query goes to superhosting.bg’s DNS as they return the IP address already set on www.superhosting.bg and the domain is loaded in the browser.
The process described above is a part of the so-called DNS recursion. This is the way to understand the domain or subdomain IP address as the content is loaded from this IP address in the browser.
It should be noted that root servers receive any DNS queries relatively rare. This is because the DNS queries are cached by DNS cache servers, but we will tell you more about them in the next article.
To be continued…:)
Tip from the support: It is а good idea to know more about the systems which are used for the website’s operation. In this way you will better understand how and why things around the web happen.
So, have we managed to reveal the mystery about what a DNS is? 🙂 If you still have any doubts, next week we are planning to release part 2. 🙂