The LDAP support currently in DSpace only supports a flat authentication structure. Many institutions use a hierarchical strcture which is slightly more complex. There is a patch on the queue that addresses this, but also tries to do a few other things so this needs teasing out. Robin from Edinburgh has also written a patch for this. Stuart Lewis will volunteer to look into this. Some LDAP-enabled applications also allow the setting of multiple LDAP servers with different settings. Is this a requirement for DSpace?