Devolution is a method which allows member computers that are part of a child domain to resolve hostnames in parent domains. Devolution creates new FQDNs by appending a single name queried like "Clints-PC" with parent suffixes for domains above it.
For example Clints-PC is in a child domain called "australia.corp.avantgardetechnologies.com.au" where avantgardetechnologies.com.au is the root domain with two child domains. I have painted this in the following diagram.
If Clints-PC goes and pings "Avantgarde-FS01" the following will happen:
Clints-PC will query Avantgarde-FS01
Clints-PC will then query Avantgarde-FS01.australia.corp.avantgardetechnologies.com.au
Clints-PC will then query Avantgarde-FS01.corp.avantgardetechnologies.com.au
Clints-PC will then query Avantgarde-FS01.avantgardetechnologies.com.au
That is DNS Devolution my friends in a nutshell, it provides member computers the ability to search up the tree using different FQDN's until it can resolve one.
Also of importance, you can configure computers with a devolution value which is represented by a number. This tells computers how far up the tree they can query before devolution will terminate. The ability to control how far up the tree termination occurs is a new feature introduced in the Windows 7 / 2008 R2 operating systems. For more information on this I recommend having a read of the following article http://technet.microsoft.com/en-us/library/ee683928.aspx
Now there are a few things you must also know about DNS Devolution. Many companies that run multiple domains generally configure a "Global Suffix Search List" with Group Policy. This specifies an order of domain names a single name resolution attempt will try and qualify itself against. For example, lets say I have a global suffix search list as follows configured on the australia.corp.avantgardetechnologies.com.au domain pushed out with Group Policy:
The second important thing you need to know about DNS Devolution is you must have "Append parent suffixes of the primary DNS suffix" check box selected under the Advanced TCP/IP settings for IPv4/IPv6.
That's it in a nutshell guys! Thanks for reading.