NA Lesson – 21

Working Mechanism of a DNS query

How a DNS Query Works? 

In general, the DNS query process occurs in two parts: 

1. A name query begins at a client computer and is passed to the DNS Client service for resolution. 
2. When the query cannot be resolved locally, DNS servers can be queried as needed to resolve the name.

  

DNS resolution method or Query resolution method

The DNS client contacts a DNS server, which then uses its own database of resource records to answer a query. However, by referring to its cache first, a DNS client can sometimes answer a

query without contacting a server at all.

Another way that DNS queries are often resolved is through recursion. Using this process, a DNS server can query other DNS servers on behalf of the requesting client in order to resolve the FQDN.

Query Example

•  The following example illustrates default DNS query behavior. 
•  In the example, the client queries its preferred DNS server, which then performs recursion by querying hierarchically superior DNS servers. Here, a client somewhere on the Internet needs to resolve the name example.lucernepublishing.com to an IP address.

Query Response Types

Queries can return a variety of answers to the client, including these, which are the most common:

■ An authoritative answer

■ A positive answer

■ A referral answer

■ A negative answer

Q. Explain how a DNS Query works? Briefly discuss the DNS resolution process.