Microsoft windows 2000 DNS manual Replicating the DNS database

•A need to delegate management of a DNS domain to a number of organizations or departments within an organization

•A need to distribute the load of maintaining one large DNS database among multiple name servers to improve the name resolution performance as well as create a DNS fault tolerant environment

•A need to allow for host’s organizational affiliation by including them in appropriate domains

The NS RRs facilitate delegation by identifying DNS servers for each zone. They appear in all forward and reverse look-up zones. Whenever a DNS server needs to cross a delegation, it will refer to the NS RRs for DNS servers in the target zone.

In the figure below, the management of the microsoft.com domain is delegated across two zones, microsoft.com. and mydomain.microsoft.com.

com edu gov ...

microsoft

mydomain ftp

... ntserver

microsoft.com Zone

microsoft.com Domain

mydomain.microsoft.com Zone

Note: If multiple NS records exist for a delegated zone identifying multiple DNS servers available for querying, the Windows 2000 DNS server will be able to select the closest DNS server based on the round trip intervals measured over time for every DNS server.

Replicating the DNS database

There could be multiple zones representing the same portion of the namespace. Among these zones there are two types:

•Primary

•Secondary

Primary is a zone to which all updates for the records that belong to that zone are made. A secondary zone is represented by a read-only copy of the primary zone.

Windows 2000 White Paper

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