10.3 System Tuning
While the default configuration values will work fine for most sites, yours may be one of the rare sites that needs some further tuning. The following tuning requires changes to the Registry. All DNS parameters referenced in this section are values of this Registry key:
10.3.1 More Efficient Zone Transfers
A zone transfer, we said earlier, comprises many DNS messages sent end-to-end over a TCP connection. Traditional zone transfers put only a single resource record in each DNS message. That's a waste of space: you need a full header on each DNS message, even though you're carrying only a single record. It's like being the only person in a Chevy Suburban. A DNS message can carry many more records.
The Microsoft DNS Server understands a relatively new zone-transfer format that puts as many records as possible into a single DNS message. The resulting "many answers" zone transfer takes less bandwidth because there's less overhead and less CPU time because less time is spent unmarshaling DNS messages.
The DNS server uses the "many answers" format by default, which is fine if all your slaves can understand it. Older BIND name servers (prior to Version 4.9.4) can't cope with this format and require the traditional one. Fortunately, you can tell the Microsoft DNS Server to use the traditional method by changing the BindSecondaries Registry value. When set to one, the server sends traditional zone transfers to satisfy older BIND servers. The default value is one, but that doesn't affect zone transfers between two Microsoft DNS Servers. They recognize each other, and the master uses the "many answers" format to the slave.
You should change this value only if you have no BIND slaves or if all your BIND slaves are running Version 4.9.4 or later.