The resource forest hosts disabled user accounts (used to enable access to Lync services). It is required that the msRTCSIP-OriginatorSID attribute for the disabled accounts maps to the ObjectSID of the account in the user forest. The resource forest topology has a higher level of isolation between Lync and the users' forest, but the increased security also implies increased administrative complexity.
This can be summarized as follows:
Also, if we have not talked about this aspect before, we have to add another point to the list.