openldap: 3+ multi datacentre replication

[hab]

Could you share any experience setting-up/expanding (large) ldap
server to multi data centres(DC)?
What strategy do you use - mesh or ring topology?
Looking for examples where 3+ DCs
with failover(master/master or master/slave) ldap setup in each DC.
Is ring topology better than mesh as ldap has to only deal with less
connections? Would be nice if you can mention any scaling issues?