DNS – Domain Name System

This article will briefly talk about DNS – Domain Name System, which is the phonebook of the internet. We will look at all the basic information about DNS – Domain Name System, the OSI Layer at which DNS falls within, the DNS query resolution process etc.

What is DNS – Domain Name System?

The Domain Name System (DNS) is the phonebook of the Internet. It is a system that translates Domain-Names / Host-Names to IP Addresses and vise-versa.

Is DNS – Domain Name System a Protocol Or a Server Role?

DNS is a Application Layer Protocol in the OSI Model.

What is a Host Table?

Every computer on the TCP/IP network has a file with the list of the Computer and equivalent IP Addresses. This file containing the Computer Names and the IP Addresses is called as Host Table.

What is the DNS Query Resolution Process?

  1. The computer first checks if the resource name is of its own.
  2. Once it finds that its not the requesting computer’s own name, the DNS resolver will proceed to the next step. The DNS resolver with then check the hosts file (/etc/hosts) to look for host name to an IP Address mapping.
  3. The DNS resolver will then check the DNS cache if it can’t find any hostname entry in the hosts file.
  4. If the DNS resolver cannot find the IP Address of the resource in the Cache, the DNS resolver will contact the DNS Server whose IP appears on the NIC configuration.

Which Windows component does DNS – Domain Name System resolution?

The resolver is a software component which is part of the Transmission Control Protocol/Internet Protocol (TCP/IP) stack that communicates with DNS Servers to create and resolve name-resolution queries.

The DNS Resolver component bundle is also available in any DNS-capable Non-Microsoft client.

DNS Resolvers exist on DNS clients and DNS Servers.

What is DNS Client (DNSCache) Service?

The DNS Client Or the DNSCache service provides the following 2 functions:

  1. DNS Name Caching: The DNS Client (DNSCache) service caches the results of the DNS Name queries.
  2. Full Computer Name Registration in DNS: The service is responsible for registering the Computer’s Full Name in the DNS.

What happens if the DNS Client (DNSCache) Service is disabled?

Disabling the DNS Client (DNSCache) services does not affect the DNS name resolution process.

The following 2 functionalities are not available if you disable the DNS Client (DNSCache) service:

  1. DNS Name Caching: Caching of the results of the DNS Name queries will not happen If you disable the DNS Client (DNSCache) service.
  2. Full Computer Name Registration in DNS: Registration of the Computer’s Full Name in DNS will not happen If you disable the DNS Client (DNSCache) service.

Want to learn more about DNS Resolvers?

Please click here if for more information from Microsoft on DNS resolvers.