Introduction to DNS

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.

# Domain name registration

When you want to host a domain with a service provider, you need to let your service provider know the name of your domain along with details of the services that you want to make available on your domain. Your service provider registers the domain name and the name servers for the domain with an ICANN-Accredited Registrar and creates the domain. When the domain is created, zones and related zone records required for the domain are automatically created.

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

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

To make a domain or zone accessible to the Internet, the domain name must be registered with at least two DNS name servers: a Master name server and a Slave name server (or backup name server).

The master name server is the primary server that serves requests for the domain.

The slave name server provides backup service when the master name server is unavailable. It receives its data for a domain from the master name server.

- Note: You can create zones and records for your site, if your service provider has enabled zone management capability for the site. If enabled, you will see the DNS option in the shortcuts section of the Home page.
  Further, your ability to manage zones and their records depend on the policy settings configured by your service provider. For example, if your service provider has disabled the add A record setting in the policy file, you will be unable to add A records. Contact your service provider if you want the settings changed.

# Managing DNS zones for your domain

If your service provider has enabled you to perform DNS-related actions for your domain, you can:

- View and modify SOA settings for a zone

- View the list of zones

- Add, refresh, and remove zones

- Add, update, and remove zone records

- View and remove DNS logs

For complete information on DNS, the following books are recommended.

- 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