How do we make user authentication take less time when using LDAP (Active Directory)?

When setting up LDAP authentication and you specify the LDAP Searches (Admin GUI->LDAP->LDAP Searches-> Base DN:) make sure to NOT use the whole domain tree, like:

DC=company,DC=domain,DC=com

but to try and narrow down the container to the one which holds the users to be authenticated to SecureTransport Server, like:

OU=users,DC=company,DC=domain,DC=com

This should speed up the authentication process and users should login to SecureTransport with less delay.