Understanding the Active Directory Driver
Applies to: Exchange Server 2010 SP3, Exchange Server 2010 SP2
The Active Directory driver is the core Microsoft Exchange component that allows Exchange services to create, modify, delete, and query for Active Directory Domain Services (AD DS) data. The Active Directory driver also uses Microsoft Exchange Active Directory Topology (MSExchangeADTopology), which allows the Active Directory driver to use Directory Service Access (DSAccess) topology data. This data includes the list of available domain controllers and global catalog servers available to handle Exchange requests. This topic discusses the relationship between the Active Directory driver and DSAccess.
DSAccess provides directory lookup services for components such as SMTP, message transfer agent (MTA), and the Exchange store. Client requests use the DSProxy service for directory access.
DSAccess implementation has several benefits that Exchange components use, especially related to topology discovery and simplification of Active Directory topology complexity. DSAccess also has several limitations related to paging of results, especially in dealing with large multivalued attributes. One of the major differences between the Active Directory driver and DSAccess is that the Active Directory driver doesn't access and store directory information in a cache. In Microsoft Exchange Server 2010, the Exchange component using DSAccess implements the appropriate cache when needed.
In Exchange 2010, the following services use DSAccess. In these cases, DSAccess is used only to obtain the current topology information and to provide a consistent topology view through all Exchange services running on the server:
Microsoft Exchange Active Directory Topology (MSExchangeADTopology)
Microsoft Exchange Information Store (MSExchangeIS)
Microsoft Exchange System Attendant (MSExchangeSA)
World Wide Web Publishing Service (WWW service or W3SVC)
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