Active Directory Web Services (ADWS) is a new windows service introduced in Windows 2008 R2 that enables remote management of any local directory service instance using WS-* protocols.

ADWS supports the following web service protocols: 

The data model used by AD Webservice is described here.

AD Webservice is automatically installed along with ADDS or ADLDS role, and is configured to run automatically when the directory instance is promoted. The Active Directory Module for Windows Powershell uses AD Webservice to manage and administer Active Directory. Also, since the new Active Directory Administrative Center (ADAC) is implemented on top of AD PowerShell, it also uses AD Webservice to manage the directory server.  This client server model is depicted in the following diagram:

Active Directory Web Services Client Server Model

As shown in the above diagram a single instance of ADWS manages all directory service instances running on the server. This includes Domain Controller, Global Catalog, Snapshot browser instances and ADLDS instances. AD Webservice is implemented using WCF and listens on the registered TCP port 9389. The service runs as a Local System with restricted privileges.

Stay tuned for more information on AD Webservice.

Cheers,
Manas Singh