Java RMI is just a set of APIs and a model for remote objects for building distributed applications. The original version of RMI uses a combination of Java serialization and the Java Remote Method Protocol (JRMP) to turn local method invocations into remote method invocations.
JRMP is one transport protocol that is used by RMI to transfer data across the network. Another example of a transport protocol used by RMI is IIOP (Internet Inter-ORB Protocol).
