• United States
Senior Editor

Extending DNS

Jun 28, 20042 mins
DNSEnterprise Applications

* A look at Dynamic DNS, or DDNS

This week’s Technology Update takes a look at one of the venerable components of the Internet: the Domain Name System. Actually it looks at a subset of the DNS if you will, know as Dynamic DNS or DDNS.

Basically DNS is a global distributed database that matches Web site URLs to a numerical IP address. DNS, which governs routing of all traffic on the Internet, contains billions of records, answers billions of queries and accepts millions of updates from millions of users on an average day.

DDNS is a mechanism that works hand-in-hand with the Dynamic Host Configuration Protocol for rapidly updating DNS. DHCP allocates IP addresses on the fly. As a result, the number and frequency of IP address changes makes manual DNS administration impractical our author ( says.

Our author says DDNS is an umbrella term for three related DNS extensions: Dynamic Update, NOTIFY, and Incremental Zone Transfer (IXFR). Dynamic Update is the basic DDNS operation, letting software such as DHCP clients or servers send special messages to name servers to update zone data. Notify lets the primary name server for a zone tell the secondary name servers that the contents of a particular zone have changed, allowing for the rapid convergence of all of a zone’s authoritative name servers. Finally, IXFR lets a secondary name server request only the changes between the version of zone data it has and the current version.

In a nutshell, these mechanisms let programs update zone data without administrator intervention. For more on this story see: