About Fully Qualified Domain Name (FQDN)
In order to let the DNS server work efficiently, all the DNS client computers must have a Fully Qualified Domain Name or FQDN. A Fully Qualified Domain Name comprises of the name of the computer a.k.a. the hostname, and the name of the domain. The hostname and the domain name are written together but are separated by a period (.). An example of a complete Fully Qualified Domain Name can be C-01.mydomain.com where C-01 is the name of the computer (hostname), and mydomain.com is the name of the domain to which the computer is added.
In case the computer is not added to the domain, or no domain exists in the network at all, the computer name is not embedded with the domain name, hence it does not become eligible to communicate with the DNS server.
When the DNS server is deployed in an organization, all the DNS compliant client computers automatically register their hostnames and their corresponding IP addresses to the DNS database. Since the DNS server becomes the repository of IP addresses and hostnames of all the client computers in the network, when any computer tries to communicate with any other computer in the network through its IP address, it sends a DNS query to the DNS server requesting for the IP address of the target computer. The DNS query is sent on the basis of the computer name of the target computer.
For example, if computer A whose IP address is 192.168.0.2 wants to communicate with the computer B whose IP address is 192.168.0.24, since the DNS server database contains the records of both the computers, the source computer (computer A) sends a DNS query to the DNS server requesting for the corresponding IP address of the computer B. The DNS server, at its part, looks for the requested computer name and its corresponding IP address in its database, and as soon as it finds the requested information, it replies back to the requesting computer (computer A) with the IP address of the computer B, which in this case is 192.168.0.24.
Once the computer A knows the IP address of the computer B, it then establishes a direct connection with the target computer and starts communicating with it.
DNS Server Types
In Microsoft’s context, the DNS server is a dedicated hardware computer running any network operating system such as Windows Server 2003, Windows Server 2008, or Windows Server 2012. However, the DNS server deployment is not only limited or restricted to Microsoft platform itself. There are many other ways through which a DNS server can be deployed in the network. A simple example can be a wireless or wired router that is present in your homes. The router that you use in your home to gain access to the Internet itself works as a DNS server.