The Domain Name System – What is it?
The Domain Name System (DNS) is a decentralized and hierarchical naming database. It provides a way for translating and mapping the domain names into IP addresses. It is compared with a phonebook, where every domain corresponds to a particular IP address. That is why it is so beneficial for humans because it is easier to remember names and not long and difficult numbers for us. Yet, machines connect and communicate with numbers. For that reason, the Domain Name System is an essential part of the Internet.
Domain Name System purpose
- Thanks to it, the use of the Internet is quick and practical.
- DNS maps the domain name to its corresponding IP address.
- Find and identify hosts on the Internet.
- It is possible to find and identify services on the Internet.
- Redundancy and load balancing.
- Verification of hosts, emails, services, and more.
- Service’s routing.
Domain Name System servers
DNS servers are the main participants in this hierarchy-built system. They are the following:
- Root servers. They are on the top level of the DNS hierarchy. Root servers respond to requests for the TLD servers. They hold the root zone file, which has data for all the TLD that are available.
- The TLD name servers. One level below the root servers is the Top Level Domain (TLD) servers, which are authoritative name servers for each TLD, such as .com, .net, .info, and so on.
- Authoritative DNS server. This server holds the original zone file for a particular zone. When asked, they are able to give an authoritative answer and establish the source of information.
- Recursive DNS servers. These DNS servers hold only copies for a short time. Their mission is to respond to queries if they have the response in their cache memory. In the other case, they assign the query to another name server, which can answer it.
DNS query explained
- A user searches for the domain name, example.net.
- If the user recently visited the domain, the answer would still be in the cache memory, and the query will be resolved. However, if it is not in the cache, the query still has to receive an answer.
- Next is the DNS recursive server of the Internet Service Provider. There is a bigger chance to find the answer in the cache of the ISP. So, the result will be delivered to the user if the answer is there.
- If there is not found the answer, the query will proceed on searching. Next is the root name server, which can provide an answer for the last part of the domain name, the TLD. It will show the name servers for that TLD. In our example, the .net TLD servers.
- The TLD name servers direct to the authoritative name server for the domain. In our case, for example.net.
- The authoritative name server, for example.net, is going to answer with the A, AAAA, or both records. Additionally, it will show the place the website is hosted.
- The user will finally be able to explore example.net. The DNS records are going to be saved on the recursive DNS servers and in the user’s device cache memory for a particular amount of time determined with the TTL.