Domain Controllers are also identified by the specific services that they provide. Windows Server 2003 uses DNS to locate domain controllers by resolving a domain or computer name to an IP address. DNS servers use the information in the SRV resource record and the A resource record to locate domain controllers. SRV resource records map a particular service to the domain controller that provides that service. The format of an SRV resource record contains this information and TCP/IP specific information. When a domain controller starts, the Net Logon service running on the domain controller uses the DNS dynamic update feature to register with the DNS database the SRV resource records for all Active Directory-related services that the domain controller provides. Therefore, a computer running Windows Server 2003 or Windows 2000 can query a DNS server when it must contact a domain controller.
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