What is a root server? Definition and mechanics

As soon as we contact an online service (like a website or an e-mail address), root name servers or (DNS) root servers take on an important role when it comes to locating the services’ address. They’re an important component of the domain name system (DNS), a fundamental column of the internet, and essential for name resolution in the DNS where the domain name (e.g. ‘www.ionos.com’) is translated into an IP address. This is a necessary process given that IP addresses are the only possible means for contacting the server of an online service and obtaining the required data from this.

But just how does a root name server help identify a website’s IP address. In order to understand the root server’s mechanics, it helps to first know a thing or two about the fundamental process of name resolution in the DNS.

In addition to an individual internet address (domain name), every internet service features a unique numeric IP address that’s connected to the domain. Following this, the IONOS website was assigned the IPv4 address, ’17.160.72.6’. When you call up ‘www.IONOS.com’ in your browser, the website’s alphanumeric name first has to be translated into the IUP address so that the browser can then present the page.

The process of name resolution

The primary role of Domain Name Systems is to translate domain names into IP addresses (also called ‘forward lookup’). The process of online name resolution creates a hierarchically organized process. However, before the DNS can be assigned to carry out name resolution, the applied system general tries to find the needed IP address within its own data.

The number of stations a request passes through and the order in which it passes depends on many different factors. Factors that can influence this process include the user’s operating system or whether or not UDP or NetBIOs over TCP/IP is used as a protocol. The name resolution itself is always processed the same way in the DNS when it runs through different servers. We’ll show you some of the most important phases that this process goes through when searching for a website’s matching IP address and which role the DNS root server plays here.

1. After you’ve initiated the calling-up process in your client, your computer’s local DNS resolver is assigned the task of name resolution. A resolver is a module that acts as an interface between an application and a DNS server. Firstly, this looks in the hosts file to see whether there’s an entry for the domain name. With the help of this text file, name resolution is able to be carried out directly via one’s own computer — at least this is the case if one manually assigns a hostname to an IP address in advanced. Given that the host file is a relic from the time before domain name systems came about and actually ended up replacing these, most users neither maintain nor use this file, which is why they don’t really help when it comes to name resolution.
    
2. If there’s no record for the requested website in the host file, then the DNS revolver’s application or operating system checks your client’s cache (buffer storage) on the domain name. If the requested website or another site registered of the same internet presence (.e.g ‘hosting.ionos.com/digitalguide) has already been booked and the information on this is still available in the cache, then the IP address is taken from this same location.
    
3. The router name server looks into its own cache to see if the IP address is stored there. However, not all router name servers have a cache. If no cache is available or there’s no IP address available, then the router name server asks the name server of its provider for the websites IP address.
    
4. By running a cross-reference with its data bank, your provider’s DNS server tries to find your domain name’s IP address. Here, different types of name server resolvers are used to gather information.
    
5. If this doesn’t lead to any result, the provider’s DNS server then turns to a root server and requests additional information via the top-level domain of the searched website (the back portion of the domain name is composed of the TLD; examples of this include .com or .de). The information on which top-level domain name servers (TLD name servers) are responsible for further announcements for a certain TLD is stored on the DNS root server in the root zone file. For the domain name ‘www.ionos.com’, the root server was sent to the Verisign’s TLD name server, as this organization is responsible for all websites with this TLD.
    
6. Next, the provider name server sends a request to the TLD name server and doesn’t receive any definitive answer. It is instead forwarded once again: the TLD name server’s sole function involves forwarding. They let requesting servers know which one of the authoritative DNS servers the desired domain name is stored on.
    
7. At this step, the provider name server turns to the authoritative server that’s responsible for the domain name and finally receives the desired IP address.
    
8. For the last step, the provider name server transfers the IP address to your router’s DNS server, which is then forwarded to your local resolver. From there, the IP address is transferred to your browser so that it can make a request to the website, load it, and display it.

When it comes to name resolution, many different name servers can be used. However, root nameservers play an important role within this process.: they depict the highest level instance within the name resolution — in case a domain name cannot be translated into an IP via a local resolver or a provider’s DNS server, the root server then becomes the starting point for locating the IP address. And even if the name resolution is always successful in the previously-mentioned step, the necessary information from the past is collected by the DNS root server and stored. For this reason, it’s important that the server is always able to carry out and support your service.

The DNS root servers described in this article refer to the root name server from the Domain Name System. This shouldn’t be confused with dedicated root servers), which can be rented through webhosting providers. Such hosts are often referred to as root servers as they differ from managed servers in that they feature a root access (more details on the differences between these two server forms can be found at the end of the article; this topic, however, is not covered in this entry.