Unlike the Directory Server’s Retro Changelog, when you change attributes in an entry, Active Directory does not report which attributes changed. Instead, Active Directory identifies entry changes by incrementing the USNchanged attribute. To detect changes to individual attributes, Active Directory and Windows NT Connectors use an in-process database called the object cache. The object cache stores a hashed copy of each Active Directory entry, which allows the Connector to determine exactly which attributes were modified in the entry.
You are not required to install Active Directory Connectors in the Windows environment. They can run also on other platforms such as Solaris or Linux and detect or make changes remotely over LDAP.