Introduction to DNS and name servers

The Domain Name System (DNS) is the mechanism that translates Internet domain names preferred by users, such as example.com, into IP addresses used by computers, such as 10.0.0.1. This translation is required because the network layer of the Internet uses IP addresses to identify domains; however, Internet users prefer to use names rather than IP addresses. More about how the Domain Name System works.

The Internet has 13 special DNS name servers called “root name servers”. The root name servers know the name servers responsible for each top-level domain.

When your computer wants to resolve a name, it sends a request to one of the root name servers asking it to resolve the name. The root name server looks at the top-level domain name, and replies with the name server who is responsible for that top-level domain. Your computer then contacts that name server, which repeats the process, either returning a translation, or returning the identity of a name server who can service the request.

# About DNS name servers

To perform domain name and IP address translations efficiently, DNS has a distributed architecture composed of many hierarchical DNS name servers. Each DNS name server is responsible for both name-to-IP-address translations (called forward lookups) and IP-address-to-name translations (called reverse lookups). Each DNS name server manages the lookups for domain name spaces. In DNS, these domain name spaces are referred to as zones. The term zone is used to denote information, such as host records, about a domain.

A reverse lookup uses the IP address to find the domain name.

A forward lookup uses a domain name to find the IP address.

To make a domain or zone accessible to the Internet, the domain name and IP address need to be registered with at least two DNS name servers: a Master DNS server and a Slave DNS server (or backup name server). You can use the Ensim Pro server or any external server as a master or slave name server. Using Ensim Pro as a master or slave name server reduces administrative overheads as Ensim Pro automatically creates zones for any site that is created on Ensim Pro.

The Secondary DNS server provides backup service when the Primary DNS server is unavailable. It receives its data for a domain from the Primary DNS server.

The Primary DNS server is the authoritative master server that serves requests for the domain.

For complete information on DNS, we recommend the following books.

- DNS and BIND, by Paul Albitz and Cricket Liu, O'Reilly & Associates, 4th Edition, April 2001

- TCP/IP Illustrated, Volume 1: The Protocols, by W. Richard Stevens, Addison-Wesley, 1994