Monthly Archives: August 2021

Recursive DNS server – definition

The DNS infrastructure is really helping the experience of Internet surfing pleasant and easy. One of the main responsible participants is the recursive DNS server. So let’s explain a little more about it and its role in the complex DNS process.

DNS – What is it for?

The Domain Name System, or DNS for short, is a well-established method of translating domain names into IP addresses. When a user wants to visit a website, it will usually search in its browser for it. To accomplish this task, the user is going to write the domain name of the website. Unfortunately, the machines don’t understand words and names, and they work only with numbers to communicate. So in the middle is the Domain Name System, and it is solving this issue by pointing the particular domain name to its corresponding IP address.

Recursive DNS server explained.

Recursion in computing is often associated with a method of solving a particular issue. Thus, it involves a program or solution that will keep repeating itself till it reaches its goal. 

Recursive DNS servers operate between the user and the authoritative DNS servers. They perform the required searches for specific information to find an answer to the queries of the users. 

As we mentioned, the users make a request for a particular domain through a browser. Yet, the process of searching for the correct IP address is performed by a recursive DNS server. Therefore, it is important to note that they are not the holders of the database with information. They are the searchers. After the recursive DNS server finds the required IP address, it gets back to the device and provides it to the browser that requested it. Finally, the device is able to connect to the IP address, and the user reaches the website.

Globally the number of recursive DNS is significant. The most popular of them are the ones of your Internet service provider (ISP).  

The two types of lookup

The recursive DNS server performs its lookup in one of two ways. They are the following:

The first type one is considered a lot easier and quicker. This is because it contains the IP address from its cache memory. For a particular time, these servers can store the information in their cache. For what amount of time they should hold it is a decision made by the administrators. They can determine more or less time by the time-to-live (TTL) value. It is all based on the strategy of the administrators actually.

Receiving the query, the recursive DNS server is going to first search for the IP address in its cache memory. If that information is still available there and the TTL has not expired yet, the assignment is completed. It is very beneficial because the response is fast, and the recursive DNS server doesn’t need to search further in other servers.

The second type of search requires a little bit more time to be completed. It occurs in the cases when the TTL in the cache is expired. For that reason, the IP address is no longer available there. However, the recursive DNS server goes a long way to obtain the desired information. It passes through the root server, TLD (Top-Level-Domain) server, and finally to the authoritative server, which is the one able to provide the answer to the query. 

Therefore, the original goal of the recursive DNS server is only to search for information.

5 most commonly used DNS records

DNS records are an essential part of managing a DNS. Every one of them has a specific and very important functionality. To achieve a perfectly working DNS, it is crucial to know what is their main purpose. Here we have 5 most commonly used DNS records that are good to know for a start. Let’s see which are they and what they do! 

SOA record

SOA for short means Start Of Authority, and it is important to know this record first. It indicates the beginning of the authority DNS zone. Inside it, you can discover information, which is crucial for the DNS zone. For the normal functionality of your DNS network, this record is a must-have. The SOA record indicates the primary DNS server. It includes data about the domain administrator and their email for contact. Also, parameters including the domain serial number and how often it should refresh. There should be only one SOA record for one DNS zone.

A record

The A record is probably the first one that comes to your mind when we are talking about DNS. Its purpose is very simple but yet essential. The A record connects the domain name (hostname) to its corresponding IP address. Every time a user wants to visit your website, will write the domain name, but what it actually needs to find is its IP address. The user’s browser will perform a search for the A record to resolve the query. Once it finds it, the browser will know exactly where the site is, and it will be able to load it to the user.

NS record

The NS (Name server) record is indicating precisely which are the authoritative name servers for a specific DNS zone. The NS record links your domain name to the hostname of the name servers. 

For example, yourdomain.net to ns1.yourdomain.net.

You need to specify which are the authoritative name servers and use the NS record. If you don’t do that, simply your DNS zone won’t work. That is the reason why we couldn’t skip this record in our list. It is crucial!

PTR record

This DNS record is also one of the must-haves in case you want to be able to send emails without problems. The PTR record has the exact opposite functionality of the A record. Also, this record is at the foundation of Reverse DNS. The PTR record points an IP address (IPv4 or IPv6) to a domain name. The need for this record appears when you send an email. The recipient requires to verify if this email was sent on behalf of the actual domain. You have to be careful when you configure your A record and PTR record because otherwise, your emails will end in the spam folder of your recipients. Nobody wants this to happen, right?

MX record

The MX record or Mail Exchanger record indicates the email server responsible for receiving emails for the exact domain. In addition, it points the domain name to the hostname of the incoming mail server. It is important to note that it is a hostname and not an IP address. You can add several MX records to create a backup if there is any difficulty. 

The reason to consider MX records is simple. Without it, you will not receive emails. For businesses, that is a pretty solid reason to care.