The DNS Server service of Windows Server 2008 provides a couple of new features and changes. In this post, I summarized them.

Background zone loading
A DNS server can now load zone data from Active Directory in the background. Essentially, this means that the DNS server can respond to requests from DNS clients before the whole DNS data is retrieved from the Directory service. This feature is only relevant for very big organizations where loading zone data can take quite some time whenever the DNS server restarts.

IPv6 support
Windows Server 2008 fully supports IPv6, the next version of the Internet protocol, and so does its DNS service. In Windows Server 2003, you have to use the “Other record” feature to add IPv6 addresses. Now, when you add a DNS record you can specify an IPv6 address or an IPv4 address in the same window. The DNS snap-in automatically creates the correct record type which is “AAAA” for IPv6 addresses. DHCP clients can dynamically register IPv6 addresses and reverse mapping is supported as well.

RODC support
I already explained this feature in my post about RODCs (read-only domain controllers). Since DNS records of a DNS server which is hosted by an RODC can’t be changed, DNS clients are redirected to a writable DNS server for dynamic updates. A DNS server on an RODC can only get its DNS data thru zone transfers or thru single record replication.

GlobalNames zone
Are you still using WINS (Windows Internet Name Service) in your organization? We do! Some applications still use single-label names (names without a dot). If you have more than one domain, you usually run into problems with such applications if they are using DNS for resolving IP addresses. The GlobalNames zone feature is supposed to be the solution for this problem. Microsoft offered a white paper for this new feature, but it seems they removed it from the Web. You can check out this discussion for more information. Based on what I read, I doubt that we will be using this feature, though. As far as I understand it, one has to create a new zone with the name “GlobalNames” and then add records manually. This would certainly be a step back, since WINS supports dynamic updates.

Link-local multicast name resolution (LLMNR)
LLMNR or multicast DNS (mDNS) enables clients to resolve names on a peer-to-peer basis within a subnet if no DNS server is available. Windows Vista also supports this feature. This certainly is nothing revolutionary. I suppose it is just a replacement for NetBIOS broadcasts. NetBIOS over TCP/IP (NetBT) is also the protocol used for WINS. So like the GlobalNames zone, LLMNR basically is Microsoft’s attempt to finally get rid of NetBIOS.

A more detailed description of the features discussed here can be found in this Technet article.

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