Before you start the process of preparing Active Directory Domain Services (AD DS) for Office Communications Server 2007 R2, ensure that your Active Directory infrastructure meets the following prerequisites:

• The domain controller in the forest where you deploy Office Communications Server runs Windows Server 2003 with SP1, Windows Server 2003 R2, or Windows Server 2008.
  
  
• All global catalog servers in the forest where you deploy Office Communications Server are running Windows Server 2003 with SP1, Windows Server 2003 R2, or Windows Server 2008.
  
  
• The forest in which you deploy Office Communications Server is raised to a forest functional level of Windows Server 2003 or Windows Server 2008. You cannot deploy Office Communications Server 2007 R2 in a Windows 2000 mixed, Windows 2000 native, or Windows 2003 interim forest.
  
  
• The domain in which you deploy Office Communications Server is raised to a domain functional level of Windows Server 2003 or Windows Server 2008. You cannot deploy Office Communications Server 2007 R2 in a Microsoft Windows 2000 mixed, Windows 2000 native, or Windows 2003 interim domain.
  
  

  Note:
  To change your domain or forest functional level, see “Raising domain and forest functional levels” at http://go.microsoft.com/fwlink/?LinkId=125762 .

Office Communications Server 2007 R2 supports the universal groups in the Windows Server 2003 and Windows Server 2008 operating systems. Members of universal groups can include other groups and accounts from any domain in the domain tree or forest and can be assigned permissions in any domain in the domain tree or forest. Universal group support, combined with administrator delegation, simplifies the management of an Office Communications Server deployment.