DNS resolver

A DNS resolver (alternatively known as Internet Service Provider's DNS resolver, ISP DNS resolver, or, simply, resolver; hereinafter, the Resolver) is any server that belongs to some Internet Service Provider that moderates any process of translating (resolving) human readable host names into IP addresses that are used in communication between Internet hosts, or vice versa.

DNS resolvers receive requests in the form of a host name from a web browser and request the needed data from root name servers, which are the highest in the hierarchy, if DNS resolvers haven't already cached that data. Indeed, DNS resolvers not only redirect requests, but also cache the data needed to identify IP addresses.

   The complete name-to-IP-address process can be described in the following way:

       When the user enters a domain name into a web browser, this browser queries their Internet Service Provider's (ISP) DNS resolver asking for the IP address.
       The DNS resolver asks the root name server where it can find details for that domain name, unless the resolver already has its IP address data cached.
       If it is asked, the root name server responds what TLD nameserver handles this data.
       The DNS resolver asks the TDL nameserver where it can find details for the entered domain name, unless it already has the data cached.
       If it is asked, the TLD nameserver responds that this data can be found at the domain nameservers.
       The DNS resolver asks the domain nameservers where it can find details for the needed IP address, unless it already has the data cached.
       If it is asked, the domain nameservers have this data and respond with a DNS record containing the IP address for the entered domain name.
       The ISP's DNS resolver sends the identified data back to the web browser. The name-to-IP-address process has been accomplished. Based on its results, the web browser points its request to the exact IP address in order to establish communication between this browser and that domain.