Do you know who to thank every time you successfully reach a website? First, to the domain name system (DNS) and then to a recursive DNS server. The DNS involves a lot of components (protocols, servers, DNS records, etc.), and all are critical for DNS processes to work precisely and efficiently.
Today let’s talk about the Recursive DNS server and its importance!
What is a Recursive DNS server?
A Recursive DNS server is responsible for searching and retrieving DNS information to answer the users’ requests. To understand its functionality better, let’s explain “recursive”. Recursion refers to a solution that will repeat itself the necessary times to fix an issue or reach a specific objective.
Why is a Recursive DNS server important?
A Recursive DNS server is vital for the DNS resolution process. Without it, millions of DNS requests around the world could remain unanswered.
Think about it like this. Someone requests a domain name through a browser by typing it in human words (exampledomain.com). Then, this DNS request will be taken by a Recursive. It will search the IP address (176.110.1.23) needed to load the required domain. Remember that machines communicate between them using numbers. Once it’s found, the Recursive will send it to the browser for reaching the domain.
This process gets repeated millions of times every single day. Internet service providers (ISPs), domain registrars, network suppliers, etc., also use such servers. Therefore, there are plenty of Recursive DNS servers around the world.
A Recursive DNS server has two options for searching and retrieving data. One takes a bit longer than the other.
The quicker option to obtain data is to search in its cache. This server can save DNS data for a specific period decided by administrators. Based on what is more convenient for the domain, the administrator can define the value for the time-to-live (TTL). When a DNS request gets generated, the Recursive DNS server will search on its cache if the corresponding IP address is still there. To find it or not totally depends on the TTL. If the time for saving the data has not expired yet, it will be there. Then the answer for the request will be really fast because the server won’t have to look for the IP address in other servers.
If the TTL has already expired, the IP address won’t be in the cache. This means the Recursive DNS server will have to search for the authoritative server that can provide it.
As you see, authoritative servers are the ones holding the DNS data. End-users are those who request DNS data. And a Recursive DNS server works exactly in between these two entities. To avoid confusion, remember, this kind of server is a searcher. That’s it! It can store information, but only during specific time periods.
Recursive DNS server risks
Cybercriminals know very well how important a Recursive DNS server is, so they exploit its use.
There are some Recursive that are public and that criminals can easily see them and target.
Criminals can use them to execute DDoS attacks like DNS poisoning, or they can directly attack the servers to shut them down.
Conclusion
Recursive DNS servers are the main components for the DNS resolution process to operate fast and for the Internet to be a nice experience, it is most of the time. It could be tough to satisfy the high demand of requests that are generated daily without them. The large number of these servers in the world is not a coincidence!