The original LDAP specification was RFC 1487, but it did not provide for communication between LDAP servers, for replication, or for advanced security. LDAP still depends on the X.500 protocols to provide the interaction and maintenance of the directory tree. The latest LDAP specification, LDAPv3, is now a draft. LDAP is also becoming Web-ready. The LDAP URL format is defined in RFC 1959, and it allows Web browser users to access LDAP directory searches as standard URLs.
Security is an issue as well.
LDAP provides simple authentication using a clear text password, and it supports Kerberos as well. This feature will allow LDAP to store public keys. Well, LDAP only provides a subset of the directory search capabilities of X.500. For example, DAP provides several ways to process queries. DAP can send the Directory information to the client for sorting, or if the directory server can't process the query, it is able to kick off a search on another server or refer the client to the server that can satisfy the request.