Almost any application build by Microsoft has a high level of integration and dependency with Active Directory; Lync Server is no exception. Lync Server cannot be installed without Active Directory and it needs certain attributes available in Active Directory. Lync Server provides wizards that help administrators properly prepare and configure Active Directory to properly support Lync Server. Following these configurations, in order, makes it easy for an administrator to deploy Lync Server successfully.
Active Directory requirements include
• All Domain Controllers (DC) in the forest must be 2003 SP2 or higher.
• The domain functional level for domains containing Lync Server must be 2003 Native or higher (not 2003 Interim). ...