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DNS Configuration and Management Manual (G06.27+, H06.05+, J06.03+)

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DNS and BIND Basics
HP DNS Configuration and Management Manual—529432-003
A-2
DNS Name Space
DNS Change Notification
BIND supports DNS change notification, also known as DNS Notify, which allows
master servers to inform slave servers that new information is available. In the original
DNS protocol, slave servers (secondaries) polled the master server at intervals defined
in the Start of Authority (SOA) record. At these defined intervals, the slave checked the
SOA record on the master server to find out if the serial number changed. If the slave
detected a change, the slave initiated a zone transfer. The disadvantage of this
approach is that slaves do not receive new information in the interim period.
The DNS Notify operation provides a method for the master server to notify slave
servers that a zone transfer is necessary. DNS Notify uses a new DNS opcode. The
notification is sent to all the hosts listed as name servers in the name server (NS)
records for the zone. Additionally, BIND allows you list additional servers to
accommodate stealth servers, which are not listed in any name server records. You
can use the zone statement to list these additional servers in the configuration file,
named.conf. When a slave server receives the Notify packet, it sends an
acknowledgment. It then behaves as if its refresh timer for that zone has expired,
undergoing the same process used during expiration time (that is, first retrieving the
Figure A-1. Structure of the DNS Name Space
Note. Throughout this document, the terms zone and domain are used interchangeably,
though they describe different concepts. A zone describes the domain name space that a
name server has authority over. Normally, a zone does not contain any delegated subdomains,
whereas a domain can contain data delegated to other name servers. Therefore, as long as
subdomains are not delegated, a zone and a domain contain the same data.
VST002.vsd
.(root)
com edu
nmt purdueinc
div cs econ
venus
indigo arthur
host
domain