Provider API
The network layer regardless of the implementation used (seda, sedang, or mina), defines protocol provider interfaces. Protocol implementors only need to implement these interfaces to plug into these framework implementations. A protocol provider essentially encapsulates the encoding/decoding of messages and request handlers (hooks) for the protocol. The networking code handles the rest to make it all work.
The directory server has one or more protocol provider implementations. The primary implementation is for the LDAP protocol. The provider is rather simple in nature and has some unique properties which make it flexible enough to be used as an LDAP proxy server or an X.500 gateway server.
Design
The server's LDAP protocol provider translates on the wire LDAP requests into JNDI LDAP operations. Results from JNDI operations are then translated to LDAP responses pushed out on the wire. This thin implementation makes the protocol layer efficient and easy to grasp.
The protocol provider is independent of the JNDI provider used. It is however dependent on the LDAP namespace. Hence it can only work with LDAP JNDI providers like the SUN LDAP JNDI provider and the server's JNDI provider.
The grunt of the work done by the protocol provider is within the request handlers. There is a request handler for each LDAP request type.