Domain Name Server (DNS), Iterative, and Recursive DNS Query

1. Overview

There are two types of queries of Domain name resolution(DNS) to issue a request for the IP address of a hostname. Then local resolver formulates a DNS query to the name server of the host. Name server checks if it is authorized to answer the query. If it is, it responds. Otherwise, it will query other name servers, starting at the root tree. When the name server has the answer it sends it to the resolver.

2. Description

2.1 Domain Name Server (DNS)

The Domain Name System (DNS) is the phonebook of the Internet. When users type domain names such as ‘google.com’ or ‘nytimes.com’ into web browsers, DNS is responsible for finding the correct IP address for those sites. Browsers then use those addresses to communicate with origin servers or CDN edge servers to access website information. This all happens thanks to DNS servers: machines dedicated to answering DNS queries.

2.1.1 What is Server

A server is a device or program dedicated to providing services to other programs, referred to as ‘clients’. DNS clients, which are built into most modern desktop and mobile operating systems, enable web browsers to interact with DNS servers. For more, see The Client-Server Model.

2.2 Recursive queries

• In a recursive query, the resolver expects the response from the name server
• If the server cannot supply the answer, it will send the query to the "closest known" authoritative name server which can be root server)
• The root server sends a referral to the "edu" server.
• Querying this server yields a referral to the server of "virginia.edu"
• and so on till find "neon.cs.virginia.edu" which is queried from resolver

2.3 Iterative queries

• In an iterative query, the name server sends a closest known authoritative name server a referral to the root server
• This involves more work for the resolver

3. References

https://www.cloudflare.com/learning/dns/what-is-a-dns-server/

https://medium.com/@leandro.almeida/dns-server-with-webmin-e189413462da

https://www.slideshare.net/shinyslide/dns-and-snmp-presentation

https://www.slashroot.in/difference-between-iterative-and-recursive-dns-query#targetText=What%20is%20a%20recursive%20query,your%20behalf%2C%20for%20the%20answer.