Besides dynamic updates, BIND 8 offers several features to enhance performance of your Domain Name System (DNS) server.
DNS has been redesigned to use BIND 8 for OS/400® V5R1. If you do not have PASE installed, you can continue to configure and run the previously released OS/400 DNS server based on BIND 4.9.3. The DNS system requirements topic explains what you need to run BIND 8-based DNS on your iSeries™ server. Using the new DNS allows you to take advantage of the following features:
In previous releases, only one DNS server can be configured. Now you can configure multiple DNS servers, or instances. This allows you to set up logical division between servers. When you create multiple instances, you must explicitly define the listen-on interface IP addresses for each one. Two DNS instances cannot listen on the same interface.
One practical application of multiple servers is split DNS, where one server is authoritative for an internal network, and a second server is used for external queries.
Conditional forwarding allows you to configure your DNS server to fine-tune your forwarding preferences. You can set a server to forward all queries for which it does not know the answer. You can set forwarding at a global level, but add exceptions to domains for which you want to force normal iterative resolution. Or, you can set normal iterative resolution at the global level, then force forwarding within certain domains.
Dynamic Host Configuration Protocol (DHCP) and other authorized sources can send dynamic resource record updates, using Transaction Signatures (TSIG) or source IP address authorization, or both. This reduces the need for manual updates of zone data while ensuring that only authorized sources are used for updates.
When NOTIFY is turned on, the DNS NOTIFY function is activated whenever zone data is updated on the primary server. The primary server sends out a message indicating that data has changed to all known secondary servers. Secondary servers can then respond with a zone transfer request for updated zone data. This helps improve secondary server support by keeping backup zone data current.
In the past, whenever secondary servers needed to reload zone data, they had to load the entire data set in an All zone transfer (AXFR). BIND 8 supports a new zone transfer method: incremental zone transfer (IXFR). IXFR is a way that other servers can transfer only changed data, instead of the entire zone.
When enabled on the primary server, data changes are assigned a flag to indicate that a change has occurred. When a secondary server requests a zone update in an IXFR, the primary server will send just the new data. IXFR is especially useful when a zone is dynamically updated. This transfer reduces the traffic load by sending smaller amounts of data.