Description: When the binding method selected is Anonymous authentication or Client authentication, the initial bind to the LDAP server is followed by a search request aimed at retrieving specific information about the user, including the user's DN, login permissions, and group ownerships. In order to retrieve this information, the search request must specify the attribute name used to represent userids on that server. Specifically, this name is used as a search filter against the login id entered by the user. This attribute name is configured here. If this field is left blank, a default of uid is used during user authentication. For example, on Active Directory servers, the attribute name used for userids is often sAMAccoutName. When the binding method selected is UPN or Strict UPN, this field defaults automatically to userPrincipalName during user authentication if the userid entered has the form userid@somedomain.