Recursive DNS server explained.

The Recursive DNS server has a significant role in the Domain Name System. So, let’s explain a little bit more about it.

What is the purpose of DNS?

The Domain Name System, or for short DNS, is a fundamental piece of the Internet. It includes a process in which the different domain names are translated into their corresponding IP addresses (IPv4 or IPv6). There are two different ways to request a domain. The first way is also the human way by using the domain names. That is an alternative for humans to memorize only the name of their requested and preferred website. The second way is also the machine way by using the IP address. They use the long series of numbers to communicate with other machines and computers successfully.

Thanks to the Domain Name System, humans are not required to remember all of the long and difficult numbers (IP addresses). We only have to write the domain names into the browser, and the website is easily reached. Yet, behind that simple operation, DNS translates for us the domain name to its IP address. So, the machines are able to understand our request, find the website, and load it for us.

What is a Recursive DNS server?

Recursion in computing is associated with a method for resolving an issue. That involves a solution or a program that is going to continue to repeat itself until it reaches its goal. The recursive DNS server is the one accountable for searching for the data needed for the answer to the DNS queries initiated by the users.

The recursive DNS servers act between the authoritative DNS servers and end-users. Every time someone types a domain name, a recursive DNS server is going to search for the IP address. After it finds the accurate IP address for the particular domain name, this server goes back to the browser of the device that initiated the request. Finally, the device is able to reach the desired website by connecting to that IP address, and the website is loaded.

Ways for performing the lookup.

The first one is definitely quicker and faster. It is performed by getting the needed answer from the cache memory of the recursive DNS server. This cache mechanism is able to keep the data from previous lookups for a particular amount of time. Usually, for how long the servers are going to cache the data is determined in most cases by the administrators. Depending on their strategy, they are able to set less or more time through the TTL (time-to-live) value. Then whenever a DNS query appears, the recursive server could check if the IP address of that specific domain name is still accessible in its cache memory. In case when the TTL is not expired yet, the information is possible to be obtained from there. That way, it saves a lot of time and does not perform a search in other DNS servers. In this situation, the DNS query is answered very fast.

The second way of performing the lookup occurs when the TTL in the cache memory is expired. That means the IP address could not be obtained from there, and the DNS recursive server has to take some steps to find the answer to the DNS query. The recursive DNS server has to find the authoritative DNS server for the specific domain name and get the needed information from there.

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