Directory System Protocol (DSP)
With a few exceptions , the DSP is vey similar to the DAP since it is used by cooperating DSA's to answer a users DAP's queries . The DSP resides at the OSI application layer , and uses ACSE to establish and release associations , and ROSE to carry protocol interactions . Again this protocol has similar operational fields such as the first , which is the Bind operation with parameters the same as in the DAP . The other basic operations that the DSP provided are:
Chained Read ,allowing the chaining of the Directory read , compare and abandon operations .
Chained Search , which allows the chaining of the Directory search and list operations .
Chained Modify , which allows the chaining of the Directory addentry , remove entry , modify entry and modify RDN operation .
The folowing diagram should clarify the way in which DSA's use the protocol to communicate .
The operation which occurs between DSA's is a chaining operation , thus each result produced by these operations is a chained result . The arguments into these operations are that of the DAP but they also include a chaining argument . These contain information about the progress of the evaluation of the operation that is needed by the next DSA in the chain . The mapping of an operation result is a chained operational result is also vey simple in that you simply add chaining result arguments to the operation .
Finally , the mapping of chained errors to operational errors must also be considered . Once an error has been detected , it is passed by DSA's to DSA's unaltered to the DUA . Certain errors may be ignored by the DSA's if there is another Access Point to which the chaining can continue .