So, what's a DNS zone?

So, what's a DNS zone?

As we have seen, the DNS is a hierarchical distributed database, the hierarchy is based in the use of domain names that allow the delegation of parts of the tree. At this point we need to introduce the concept of zone that the RFC 1035 defines as:

The complete database for a particular "pruned" subtree of the domain space.

Each zone is under a single authority and it can delegate the management of a part of the tree. The origin of the DNS tree is the root zone that contains the delegations for all the TLDs. Each TLD constitutes at the same time a new DNS zone, and the same applies to second level domains and so on. Each zone can be under a different authority. For example:

Diagram of the DNS structure

In this scheme we can see the different levels of the DNS structure, on top, at the origin, there is the root zone, which is managed by ICANN and contains the delegations to the TLD zones, these contain the delegations for each domain (domain1, domain2, etc...) which constitute separate zones and so on with the subdomains.

The zones contain information about the resources that make the zone, and each zone is divided in Resource Records (RR), this information is stored in the the zone file