DNS Name Server Enhancements: DNS Notify, Incremental Zone Transfers, and DNS Update (Dynamic DNS)
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The fundamentals of operation of Domain Name System servers, as explained in the preceding topics in this section, are specified in the main DNS standards, RFC 1034 and 1035. These documents are pretty old by computer industry standards; they were published in 1987. To the credit of the designers of DNS, most of what they originally put into the DNS protocol is still valid and in use today. The creators of DNS knew that it had to be able to scale to a large size, and the system has in fact successfully handled the expansion of the Internet to a degree far beyond what anyone could have imagined 15 or so years ago.
As originally defined, the Domain Name System requires that DNS information be updated manually by editing master files on the primary server for a zone. The zone is then copied in its entirety to slave servers using a polling/zone-transfer mechanism. This method is satisfactory when the internetwork is relatively small, and changes to a zone are made infrequently.
However, in the modern Internet, large zones may require nearly-constant changes to their resource records. Hand-editing and constantly copying master files can be impractical, especially when they grow large, and having slave servers get out of date between zone transfers may lead to reliability and performance concerns. For these reasons, several enhancements to the operation of DNS servers have been proposed over the years. I'm going to take a closer look at three of them here.
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