• It is a phonebook of the internet
• Humans access information online through domain names
• DNS translates domain names to IP addresses so browsers can load internet resources

How does DNS work ?

• It involves converting a hostname (www.example.com) into a computer-friendly IP address (such as 198.168.1.1)

Types of Domains

1. Generic Domain

• .com(commercial), .edu(educational), .mil(military), .org(nonprofit organization), .net(similar to commercial)

2. Country Domain

• .in (India) .us .uk

3. Inverse Domain

• It is used for mapping an address to a name

• Sends query to DNS server

DNS Server

DNS Resolver

• DNS cache (sometimes called DNS resolver cache)
• It is a temporary database maintained by computer operating system that contains records of all recent visits and attempted visits to websites and other internet domains
• It receives the request to resolve the domain name with the IP address

  Root Name Server

• 13 sets of servers named as letter.root-servers.net
• Details of all root name servers can be found at www.root-servers.org
• It receives the first request and lets the DNS resolver know the address of the Top Level Domain (TLD) that stores information about the site
• .com and .net are like TLDs`

TLD name server

• The DNS resolver then queries this server, returning the Authoritative Name Server where the site is returned

Authoritative Name Server (ANS)

• Finally, the DNS resolver queries this server to learn the actual IP address of the website you’re trying to deliver