How are data and references to objects actually communicated across process boundaries?

Data and references to objects are communicated across boundaries using a protocol called IIOP (Internet Inter-ORB Protocol). IIOP is a concrete implementation of the GIOP (General Inter-ORB Protocol) and is based upon TCP/IP.

Every language that is CORBA compliant has a defined mapping to communicating via IIOP (e.g. Java, C++, Delphi, COBOL). This protocol is used to communicate across process boundaries.

For CORBA objects that communicate within a process, optimizations are made within quality ORB's to reduce any unnecessary overheads.