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Domain Name System (DNS)

What is DNS?

DNS stands for Domain Name System. A DNS translates or resolves a hostname (eg. www.zoho.com) into a language of numbers that a computer can understand (eg. an IP address).

What is a DNS registrar?

A DNS registrar is an entity that is authorized to facilitate the buying and selling of domain names. They are responsible for mapping IP addresses to domain names. A few examples of DNS registrars are GoDaddy, HostGator, Bluehost, and Domain.com. The database of these IP addresses and domain names is managed by domain registries like Verisign and Public Interest Registry. They manage the Top Level Domains (TLD), which refers to domains that end in .com, .net, and .org.

What are Nameservers?

Nameservers are physical servers that hold information about IP addresses and respective domain names or URLs. They are the foundational units of a DNS.

When a user searches for www.zoho.com on the Internet, the DNS servers lookup for an IP address linked to this domain and render the requested website on the web browser.

There are four types of DNS servers that communicate with each other to resolve a query. They are the:

  • Recursive DNS resolver
  • Root Nameserver
  • TLD Nameserver
  • Authoritative Nameserver

How does DNS work?

Step 1

When a query for a domain (www.zoho.com) is made from a web browser, it's forwarded to the DNS resolver.

Step 2

The DNS resolver checks its cache to resolve the query. If it finds the IP address of the requested domain in cache, the query is resolved and www.zoho.com is displayed on the web browser.

Step 3

If the requested domain is not stored in the cache of DNS resolver, the query is forwarded to the Root Nameserver. The Root Nameserver looks for the extension like '.com', '.net', or '.org' and shares the IP address of the TLD Nameserver with the DNS resolver. It then stores information about the requested extension in its cache.

Step 4

The TLD Nameserver then runs a query and shares the IP address of the Authoritative Nameserver that stores the IP address of the requested domain (www.zoho.com).

Step 5

The Authoritative Nameserver resolves the domain query and the website is displayed on the web browser.

What are DNS records?

DNS records are instructional files on how to handle incoming queries. Some common DNS records are the A Record, CNAME Record, TXT Record, and SRV record.

Note: If the web-hosting provider or the DNS registrar is changed, the DNS server is also changed. Then you must switch your DNS records with the new host.

What is the role of DNS in sending emails?

DNS holds information that helps with email delivery, authentication, and encryption.

  • Email delivery - The domain name in the email address is matched to the IP address. This enables email delivery.
  • Email authentication and encryption - DNS records like SPF, DKIM, and DMARC verify the senders as well as identify and encrypt the email content to ensure all emails are secured.