In this system there is a DNS hierarchy of domain names and each site is only responsible for maintaining the information of its domain. That is why it is considered to be a distributed system. In this hierarchy, each part of the name, that is, each domain is separated by a period (.). The leftmost part is the most specific. For example, in www.example.org, the leftmost name represents a server and is the most specific part within the example domain, which in turn is within the org domain (the least specific part of that name).
For the practical operation of the DNS system, three main components are used:
▸Clients phase 1
A DNS client program that runs on the user’s computer that generates DNS name resolution requests to a DNS server.
▸DNS Servers
That answer customer requests. Recursive servers have the ability to forward the request to another server if they do not have the requested address.
▸Zones of authority
It is a part of the domain name space that a DNS server is responsible for, which can have authority over several zones.
The client software initiates a DNS resolution (in response to requests from other software running on the computer) to access some computer by name. The configuration of a resolver is simple and you only need the IP address of a recursive server. The recursive server is the one that receives the DNS queries from the resolvers and is responsible for executing the resolution to return the final response to the client (resolver). Recursive servers query servers until they get the answer to the query.
Finally, the authoritative server is the one that has authority over a domain name. In other words, it is the reliable source of information for a domain name. It contains information on which IP addresses are associated with computers that use the domain name in question.
Also see:
DNS Tunneling – A Data Encoder Attack Method
