DNS Name Space Administrative Hierarchy Partitioning: DNS Zones of Authority
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The Impact of Zones on Name Resolution: Authoritative Servers
The concept of zones is critical to understanding how DNS name servers work, and therefore, how name resolution is performed. All of the information about the subdomains and individual devices in the zone is represented using a set of resource records stored on a DNS name server. Usually, this name server is associated with the highest-level domain name in the zone. A name server that contains the definitive information for the zone is said to be authoritative for the zone. An authoritative server for a zone is one that maintains the official information about the zone, and the one that is ultimately responsible for providing name resolution information about it. We'll see more about this in the section on DNS servers and name resolution.
Every DNS zone has a set of authoritative servers, which are usually a pair called the primary (or master) and secondary (or slave) servers. However, it is also possible for a single DNS name server to be authoritative for more than one zone. As mentioned above, it is not always necessary for the actual owner of a domain to provide DNS services for it. Very often, especially for the domains owned by small businesses or individuals, DNS services are provided by a third party, often an Internet Service Provider.
For example, I have had pcguide.com registered as a domain since 1997, but my long-time Web hosting provider, pair Networks, has provided DNS services for me since the beginning. This means that pair's DNS servers in the pair.com hierarchy are responsible for pcguide.com. They are also responsible for many other domains for their customers.
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