Apache Directory Server
An extensible, embeddable LDAP and Kerberos server, entirely in Java
ApacheDS is an extensible and embeddable directory server entirely written in Java, which has been certified LDAPv3 compatible by the Open Group. It has been designed to introduce triggers, stored procedures, queues and views to the world of LDAP which has lacked these rich constructs.
Java
Lightweight Directory Access Protocol (LDAP): The Protocol
IETF
RFC 4511
The Kerberos Network Authentication Service (V5)
RFC 4120