It is the phonebook of the internet (Converts Domain Names to IP Addresses)
Domain Names
gTLD (Generic Top Level Domain) - .org
, .com
, .edu
ccTLD (Country Code Top Level Domain) - .in
, .co.uk
Second Level Domain can only be 63 characters long
They can only contain alphanumeric characters and hyphens
Subdomains sit below second level domains and have the same naming restrictions
There is no limit on the level of subdomains that can be created
The entire domain name most be 253 characters or less
DNS Working
Check Web Browser & OS Cache for IP Address
Send request to DNS Recursive Resolver (ISP) - Checks own Cache for IP Address
Send request to Root Server - Knows location to Top Level Domain (TLD) Server
Resolver is directed to TLD - Knows location of Authoritative Name Servers
Resolver is directed to Authoritative Name Server - Returns the IP Address of Domain
Resolver (ISP) caches the IP Address - Sends IP to requesting device
We can configure our devices to use a third-party DNS Resolver
If the Autoreactive Name Server returns a CNAME (alias) than the Resolver has to perform the whole process again for the alias