Authoritative vs Non Authoritative DNS debate looks like a little complicated. However we will try to make it easy for you. Authoritative DNS is server that is maintained by the original domain owner. It contains the actual zone files which are used to resolve any DNS queries relate to that domain. On the other hand a non authoritative DNS is just an ordinary DNS that helps the requester to resolve the domain name through authoritative DNS server. Here is an example,

216.239.36.10 is authoritative DNS for google.com. When we ask it to resolve www.google.com. It goes to its zone file finds the appropriate record 192.178.24.132 and return it to user. Since we can not find a word “Non-authoritative” in its response this because 216.239.36.10 authoritative server for google.com.

Now we are sending the same query to resolve www.google.com to a different server (8.8.8.8 this time). It resolved the domain name for us and return the same result that is 192.178.24.132. But you will find a little difference in response. A new line “Non-authoritative answer”. The reason is 8.8.8.8 is not authoritative DNS server for google.com.

A a non-authoritative DNS in the backend, goes to the authoritative DNS get the query resolved though it and sends the response to the requester. It also keep the result of query in its own cache so that next time if someone requests same, it will used its own caches instead of going to authoritative DNS every time. The process is call DNS caching. DNS caching improves the response time and performance for internet users. All modern DNS servers have caching feature. Some DNS servers does not have any zone information at all . It means they are not authorities for any zone/domain. We call them caching only DNS servers. Internet service providers across the word frequently use caching only DNS servers for their clients.

You need to query NS record to find the authoritative DNS server for a particular domain. For example if you want to search name servers/ authoritative DNS of google. you need to run “nslookup -q=ns google.com” on command line. Following is the output of command.

A easier web based tool might also help. Go to “http://pingstage.com“. Simply type the domain name. Select NS in record type and lookup.

Original domain owners manages the authoritative DNS servers. They create, deleted or modify DNS records. In short it is their responsibility to make sure the zone file updated all the time. However non authoritative DNS servers do not have such responsibility. They fully rely on authoritative DNS server to obtain the correct information and give it to their clients when needed. But they still maintain the their local cache so that they don’t need to go to authoritative server frequently.

A DNS server can have many other records beside NS record. If you want to learn more about different type of DNS record we recommend you to visit “DNS Server – A detailed introduction“