Incremental Transfers—Multimaster replication

Incremental Transfer is for rapid propagation of changes to a DNS database. Windows NT 4.0 does not support the Incremental Transfer protocol, however it will be supported in the future. The Incremental Transfer protocol is designed to reduce latency and decrease the amount of data send during a zone transfer. It does this through two mechanisms.

Notification is used to actively notifying servers of a change to a zone file. The notification is accomplished by the NOTIFY extension of DNS (Microsoft DNS support Notify in Windows NT 4.0). For more information on the notify specification refer to the Internet draft on http://ds.internic.net/internet-drafts/draft-ietf-dnsind-notify-07.txt.

Zone propagation is improved by sending just the information which has changed. This is a much better method than the current full zone transfer mechanism, since the current method always transfers the entire zone file. For more information on the Incremental Transfer protocol see the Internet draft on http://ds.internic.net/internet-drafts/draft-ietf-dnsind-ixfr-06.txt.

The replication of dynamic data will work very similar to the way that WINS works today, however the data stays within the zone instead of replicating unnecessary data to each and every server (like WINS). The following figure displays the resolver registration and how replication will work:

The dynamic database for L200.acme.com only replicates between DNS server 2 and DNS server 3. The dynamic database for Dallas.acme.com only replicates between DNS server 1 and DNS server 2.