Overview of DNS

Domain name translation is fundamental to Internet usage. The Internet recognizes domains as IP addresses; however, Internet users prefer to use names, rather than IP addresses, to identify domains. Consequently, the domain names that users specify must be translated into IP addresses for use by the Internet. The Domain Name System (DNS) is the mechanism that makes this translation.

Lookups

DNS is a distributed database that performs name translations. To manage this information effectively DNS has a distributed architecture composed of many DNS servers in a hierarchical fashion. Each server is responsible for both name-to-IP-address (forward) and IP-address-to-name (reverse) translations (called lookups).

The DNS system is, in fact, its own network. The important point is that it is a distributed network. Thus, no single server or organization has or owns the DNS information of the Internet. If one DNS server does not know how to translate a particular domain name, it asks another one, and so on, until the correct IP address is returned.

Zones

Each DNS server manages the lookups for one or more domain name spaces, called zones.

Records

Each DNS server also maintains a list of all domain names and their associated IP addresses. The elements on this list are known as records. Once you have created a zone, you add records to that zone. A zone can contain the following types of records:

Start of Authority (SOA) records

Each DNS zone has a Start of Authority (SOA) record. When you add a zone to a domain, a SOA record is automatically created.

The SOA record: