Apple Mac OS X Server (Administrator’s Guide) - Manual (Page 515)

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DNS Service
When your clients want to connect to a network resource such as a Web or file server, they
typically request it by its domain name (such as www.example.com) rather than by its IP
address (such as 192.168.12.12). The Domain Name System (DNS) is a distributed database
that maps IP addresses to domain names so your clients can find the resources by name
rather than by numerical address.
A DNS server keeps a list of domain names and the IP addresses associated with each name.
When a computer needs to find the IP address for a name, it sends a message to the DNS
server (also known as a name server). The name server looks up the IP address and sends it
back to the computer. If the name server doesn’t have the IP address locally, it sends
messages to other name servers on the Internet until the IP address is found.
Setting up and maintaining a DNS server is a complex process. Therefore many
administrators rely on their Internet service provider (ISP) for DNS services. In this case, you
only have to configure your network preferences with the name server IP address provided
by your ISP.
If you don’t have an ISP to handle DNS requests for your network and either of the following
is true, you need to set up DNS service:
m You do not have the option to use DNS from your ISP or other source.
m You plan on making frequent changes to the namespace and want to maintain it yourself.
m You have a mail server on your network and you have difficulties coordinating with the
ISP that maintains your domain.
Mac OS X Server uses Berkeley Internet Name Domain (BIND) for its implementation of
DNS protocols. BIND is an open-source implementation and is used by the majority of name
servers on the Internet.