http://www.ietf.org/internet-drafts/draft-ietf-nfsv4-federated-fs-protocol-01.txt
Our schema is sprinkled throughout Section 6. In Section 6.3 we define
two LDAP objects, the FSN and FSL (the exact schema definitions in the
current draft have some typos that will be cleaned up in the next
version).
An FSN is intended to be superior to its FSLs in a DIT. I was
considering including DIT Structure Rules in the draft as a way to
enforce this arrangement. However, I'm not inclined to do this if
popular LDAP implementations, such as OpenLDAP, don't support them.