There are 5 Active Directory Roles in Windows Server 2008
· Active Directory Certificate Services
· Active Directory Domain Services
· Active Directory Federation Services
· Active Directory Lightweight Directory Services
· Active Directory Right Management Services
Active Directory Certificate Services increases data security by allowing a private key to be combined with users, groups, computers, routers or services.
Active Directory Domain Services stores all of your domain objects like users, groups, computers on a network. It is a centralized tool to manage objects.
Active Directory Federation Services provides internet-based clients a secure identity access solution for Windows and non-Windows systems.
Active Directory Lightweight Directory Services uses LDAP protocol for querying and modifying directory services.
Active Directory Right Management Services improves security for email messages, internal documents and websites by
