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, an Active Directory Connector uses 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 on Windows. These connectors can also run on other operating systems such as Solaris or Red Hat Linux, and detect or make changes remotely over LDAP.