I would also note, that in OpenLDAP 2.6+, "standard" syncrepl is the safer replication mechanism for multi-provider environments. While in the past, I always went with delta-syncrepl, for my last roles, I've used OpenLDAP 2.6 + standard syncrepl.I find standard syncrepl is often best, since it's so much simpler to set up. And many sites only have single digit megabytes or less amount of write traffic per day. Of course not all (like a telco I know well), but if the amount of write traffic is low, then delta-syncrepl is an unnecessary complication. In a recent client I worked for who has servers in three continents, we were able to maintain total consistency within 1 second, for any given change.
-- Chris Paul | Rex Consulting | https://www.rexconsulting.net