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Directory System Agent (DSA)

Definition - What does Directory System Agent (DSA) mean?

A Directory System Agent is a set of services and processes that is used to provide access to a data store. DSA runs on domain controllers and allows the user agents to access the physical storage of the data located on the hard disk. It supports certain mechanisms that allow the clients to access directory data. It is widely used by the Lightweight Directory Access Protocol (LDAP) for providing directory services in a network.

Techopedia explains Directory System Agent (DSA)

DSA is a set of software services and process that is part of the X.500 directory service. Each domain controller has its own DSA and each DSA takes care of the directory information for a single organizational unit. It is an essential part of the local system authority (LSA) sub-system in the Active Directory Domain Services. DSA was introduced in Windows 2000 servers and later in domain controllers. It is verified on the various server platforms like Windows Server 2012, Windows server 2008 R2 and Windows Server 2008.

Some of the protocols used by clients to connect to DSA are:

  • LDAP version 3.0
  • LDAP version 2.0
  • Security Account Manager interface
  • MAPI RPC interface
  • Proprietary RPC interfaces

The LDAP clients make use of the respective protocol to connect with DSA services. Both the Windows clients and Active Directory Domain services support LDAP 3.0.

DSAs make use of the remote procedure call interface to perform the replication operation and connect to each other in the Active Directory Domain services.

MAPI clients like Microsoft Exchange Server use the MAPI Remote Procedure Call interface.

DSA is a significant part of the directory services that helps in converting the raw information to user-readable LDAP. The three most common usages of DSA are from LDAP clients, MAPI clients and replication among the DSAs.

The specifications of DSA are included in the International Telecommunication Union (ITU-T) X.501.

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