Difference between a Zone and a Domain

Difference between a Zone and a Domain

The difference between a zone and a domain is often poorly
understood. Consider the domain tree shown in Figure 1. It shows the
example.com domain with subdomains development.example.com and
advertising.example.com. The development domain has three
subdomains and advertising another two.


The root domain, example.com is the parent to the development and
advertising domains, each of which is a subdomain of example.com.
These two subdomains are themselves parent domains to their own set
of subdomains, namely, resources, documentation, coders, design and
sales. Thus, the fictitious company, example.com, is divided up into
multiple domains allowing easier administration and greater
geographical versatility.
In addition to the primary and backup domain controllers that exist in
each domain, there will typically be one or more Domain Name System
(DNS) servers, or name servers, responsible for the domain. However,
unlike domain controllers, there does not need to be a name server for

each domain, instead name servers are allocated zones that can
comprise of one or many domains. Thus a domain cannot contain a
zone but a zone can contain one or more domains, the two being
definable in the following way:
• A domain represents one branch of the DNS name space
• A zone is a contiguous portion of the name space.
All the hosts within a zone have their name and IP address stored on
the primary name server and are configured to look to this or a
secondary name server when name resolution is required.
Name servers responsible for a zone are said to be authoritative for that
zone. The primary name server will always hold the most current zone
file and secondary name servers are typically configured to send zone
transfer queries to this server though another secondary name server
could be used instead.