Domain Name System (DNS) is the name resolution tool used in computer networks. It is more like a phone book. You remember the names of your contacts, and all other details, like the phone number, e-mail, address are all saved in the phone book, and it will become very daunting for anyone to remember all the details of every contact. The same is the case in computer networks. Imagine, every time you wanted to connect to a website or an application, you had to key in its IP address, instead of writing simple names, for examples, to log in to google.com you had to type in 126.96.36.199 (it is one of the IP addresses used by Google). And also think about how many different IP addresses you had to remember for all the websites and applications that you access in your routine. In that case, most people would have turned away from using computers.
TCP/IP defined a solution to this problem – DNS. When we send an IP packet to, say, www.google.com, the IP packet does not contain the name as the destination IP, it still contains the IP address, and this IP address is provided by the DNS server. In the first step in name resolution, PC sends a DNS query to the DNS server, and the DNS server responds with the DNS reply after having resolved an IP address for a name, the information in this might have come from the DSN Server Cache. This is categorised as an iterative query. There are two more types of DNS Queries – Recursive and Inverse. When the DNS server cannot resolve the IP address on its own, it follows a long path of contacting the root DNS and other DNS servers which might contain the information about the specific name. It is called a recursive query. At times, we know the IP address and want to know the IP address associated with it, the inverse query comes in handy then.
Additionally, we don’t have to worry if a website changes its web server, which changes its IP address as well. And if we don’t know the correct IP address, then we might get redirected to a malicious website, which can pose serious security issues. In this case, also, the DNS server will help us reach the website by resolving the new and correct IP address. DNS also provides security to the web server by masking the IP address. If an attacker knows the IP address, and the ports of the server are not secured properly, then the server can be accessed from anywhere.
The entire DNS process, along with its uses, seems to be a very long process, but in reality, it is completed in just a few seconds at the maximum.
List of top IT Certification