What is the Difference Between Authoritative and Recursive DNS

The main difference between authoritative and recursive DNS server is that the authoritative DNS server performs the mapping of the domain names to IP addresses while the recursive DNS server takes the requests from the user and checks the records from authoritative DNS to find the corresponding IP address.

DNS is a type of server that manages and maintains the internet domain names and their associated IP addresses of computer services and devices of the network. It is an essential component to maintain the proper functioning of the internet. Authoritative and recursive are two types of the DNS servers. Authoritative DNS provides answers to requests made by other DNS name servers (Recursive Servers) with the IP mapping of the intended website. But, the recursive DNS performs several lookups to respond with correct IP for the host. Organizations such as Google run their own public Recursive DNS servers.

Key Areas Covered

1. What is DNS
     – Definition, Functionality
2. What is Authoritative DNS Server
     – Definition, Functionality
3. What is Recursive DNS Server
     – Definition, Functionality
4. What is the Difference Between Authoritative and Recursive DNS
     – Comparison of Key Differences

Key Terms

Authoritative DNS, DNS, IP Address, Recursive DNS

What is DNS

IP address is a numerical address that helps to identify the devices connected to the internet. However, it is not always possible to use the IP address to recognize the devices. Therefore, Domain Name Server (DNS) is an alternative to this issue. It connects domain names to corresponding IP addresses. To be specific, when the user enters a domain name in the web browser, the DNS server converts the domain name to the IP address. For example, when the user types google.com in the web browser, the DNS server searches its database to find the matching IP address for that domain name. Then, it resolves the domain name to the IP address of the website. Finally, the user can communicate with the google.com.

Figure 1: DNS Server

Furthermore, there are two types of DNS servers. Namely, they are authoritative and recursive servers. The difference between authoritative and recursive DNS server depends on their classification according to how the server responds to the queries and holds the information that says which IP address maps to which domain.

What is Authoritative DNS Server

An authoritative DNS server stores the “maps” of the domain names in IP addresses. A system administrator performs the mapping of domain names to IP addresses. If a user has his own domain name, at some point he will need to use an authoritative DNS server to map the domain name to an IP address. This is only done on an authoritative DNS server.

Moreover, authoritative DNS servers are configured in a hierarchical structure. Everything begins with the dot root name servers. DNS is maintained by a distributed database system, and the nodes of the database are called the name servers. Authoritative name servers know where to find the level set in the hierarchy, e.g. – top-level domains. In addition, the root servers are at the top of the DNS tree.  They know exactly which IP addresses of the authoritative servers are the ones that handle DNS queries for Top Level Domains (TLD) such as .com.

What is Recursive DNS Server

Recursive DNS servers provide the proper IP address of the intended domain to the requesting host. For instance, consider a user request for a website via a web browser. First, the computer makes a request to the recursive DNS server to find out the IP address associated with the website. It is assumed that the operating system and web browser do not already have it cached. Then, the recursive server checks if the IP is cached and still has a valid time to live (TTL). If the recursive server does not have IP cached, then it starts the recursive process or the repeating process of going through the authoritative DNS server hierarchy.

Difference Between Authoritative and Recursive DNS

Definition

An authoritative DNS server is a server that responds to DNS queries from data that has been configured by an original source such as a domain administrator or DNS methods. Meanwhile, recursive DNS server is a server that takes the website name or URL from users and checks the records obtained from authoritative DNS servers to figure out the corresponding IP address. Thus, this contains the main difference between authoritative and recursive DNS.

Functionality

Authoritative servers have direct access to root name servers. However, recursive servers already have the information stored or cached. Therefore, this is a major difference between authoritative and recursive DNS.

Management

Another difference between authoritative and recursive DNS is that, in authoritative DNS server, the mapping of the domain name to IP address is configured by system administrators. In contrast, recursive DNS servers are managed by ISP or speciality resolving DNS providers.

Conclusion

In conclusion, authoritative and recursive servers are two types of DNS servers. The main difference between authoritative and recursive DNS server is that the authoritative DNS is a server that performs the mapping of the domain names to IP addresses while the recursive DNS is a server that takes the requests from the user and checks the records from authoritative DNS to find the IP address.

Reference:

1. “Domain Name System.” Wikipedia, Wikimedia Foundation, 3 Oct. 2018, Available here.
2. “What Is Recursive DNS Server? – Definition from WhatIs.com.” WhatIs.com, Available here.

Image Courtesy:

1. “Dns-server-upload” By Б.Өлзий – Own work (CC BY-SA 4.0) via Commons Wikimedia