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 whereas the recursive DNS server takes user requests and checks the records of the authoritative DNS to find the corresponding IP address.

DNS is a type of server that manages and maintains Internet domain names and their associated IP addresses of computer services and network devices. It is an essential component to keep the internet running smoothly. Authoritative and recursive are two types of DNS servers. Authoritative DNS provides responses to requests made by other DNS name servers (recursive servers) with the IP assignment of the intended website. But, recursive DNS performs multiple lookups to respond with the correct IP for the host. Organizations like 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

The IP address is a numerical address that helps identify devices connected to the Internet. However, it is not always possible to use the IP address to recognize devices. Therefore, Domain Name Server (DNS) is an alternative to this problem. Connect the domain names to the 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 IP address corresponding to that domain name. It then resolves the domain name to the IP address of the website. Finally, the user can communicate with google.com.

                                                                Figure 1: DNS Server

Also, there are two types of DNS servers. Namely, they are authoritative and recursive servers. The difference between an authoritative and recursive DNS server depends on its classification based on how the server responds to queries and contains the information that indicates which IP address is assigned to which domain.

What is authoritative DNS server?

An authoritative DNS server stores “maps” of domain names to IP addresses. A system administrator performs the mapping of domain names to IP addresses. If a user has their own domain name, at some point they 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.

Also, the authoritative DNS servers are configured in a hierarchical structure. It all starts with dot root nameservers. DNS is maintained by a distributed database system, and the database nodes are called nameservers. Authoritative nameservers know where to find the level set in the hierarchy, eg – Top Level Domains. Also, root servers are located at the top of the DNS tree. They know exactly which authoritative server IP addresses are handling DNS queries for top-level domains (TLDs) like .com.

What is Recursive DNS Server

Recursive DNS servers provide the correct IP address of the desired domain to the requesting host. For example, consider a user request for a website through a web browser. First, the computer makes a request to the recursive DNS server to find out the IP address associated with the website. The operating system and web browser are not supposed to have it cached yet. The recursive server then checks if the IP is cached and still has a valid time to live (TTL). If the recursive server has no cached IP, then it starts the recursive process or the iterative process of going through the authoritative hierarchy of the DNS server.

Difference Between Authoritative and Recursive DNS

Definition

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

functionality

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

management

Another difference between authoritative and recursive DNS is that on the authoritative DNS server, the domain name to IP address mapping is configured by system administrators. In contrast, recursive DNS servers are managed by ISPs or specialized DNS resolver 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 authoritative DNS is a server that does the mapping of domain names to IP addresses while recursive DNS is a server that takes user requests and checks the records. authoritative DNS to find the IP address.

Reference:

1. “Domain Name System.” Wikipedia, Wikimedia Foundation, October 3, 2018, Available here.
2. “What is recursive DNS server? – Definition of WhatIs.com. WhatIs.com, available here.

Courtesy image:

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