This scenario represents the case where the LDAP server is located inside the organization LAN whereas Platform has been installed in cloud.
Consequently:
the LDAP must be accessible though the Internet , so that Platform can communicate with it; typically, a VPN is used to make them communicate with each other
users must be extracted by the LDAP server and loaded into the Platform database
Platform must be configured in order to:
import users from the LDAP on a regular basis
access to the LDAP server remotelly, in order to authenticate users