How to know the root of LDAP?

["Ning Ling" <ning@gsta.com>]

Hi, everybody.
Is there any method to get the root of LDAP Directory in LDAP RFCs? I want
to do this because I am working with the MCIS(Microsoft Commercial Internet
System). I want to replace the LDAP Server with OpenLDAP without changing
the system.  But the manage tools from microsoft cannot recognzine OpenLdap
if I don't specify the base dn. And I can not specify it in a site server
MMC. Did any body here had ever met such problem?
Thank you very much.

Ning Ling