To configure Microsoft SQL Server JDBC Driver Version 6 with Kerberos, using Windows 2008 or Windows 2012, in the Domain Controller, open Active Directory Domains and Trusts, then right-click the active domain and select raise domain functional level.
This enables the domain to support delegation and SPNs (Service Principal Names), as well as higher encryption levels.
If there is more than one domain controller, you will have to wait until the changes are propagated to the other domain controllers. You can confirm this by examining the Windows Event Log on the primary domain controller, and opening the Windows Event log. Scroll down and expand Applications and Services Logs, select DFS Replication and ensure no error messages have occurred. Additionally, check the information messages for a time stamp near your changes. Look for Event ID 1206, the text should have the name of the PDC (Primary Domain Controller) and a success message.
For more information, see the Raise the Domain Functional Level section in the Microsoft Developer Network website at https://msdn.microsoft.com/en-us/library/cc753104(v=ws.11).aspx, or see the Kerberos Enhancements section at https://technet.microsoft.com/library/cc749438(ws.10).aspx