Evaluating policies and mechanisms for supporting embedded, real-time applications with CORBA 3.0

To be an effective platform for performance-sensitive real time systems, commercial-off-the-shelf (COTS) distributed object computing (DOC) middleware must support application quality of service (QoS) requirements end-to-end. However, conventional DOC middleware does not provide this support, which makes it unsuited for applications with stringent latency, determinism, and priority preservation requirements. It is essential, therefore, to develop standards based, COTS DOC middleware that permits the specification, allocation, and enforcement of application QoS requirements end-to-end. The Real-time CORBA and Messaging specifications in the forthcoming CORBA 3.0 standard are important steps towards defining standards based COTS DOC middleware that can deliver end-to-end QoS support at multiple levels in distributed and embedded real time systems. However these specifications still lack sufficient detail to portably configure and control processor, communication, and memory resources for applications with stringent QoS requirements. The paper provides four contributions to research on real time DOC middleware. First, we show how the CORBA 3.0 Real-time and Messaging specifications provide a starting point for addressing the needs of an important class of applications with stringent real time requirements. Second, we show how the CORBA 3.0 specifications are not sufficient to solve all the issues within this application domain. Third, we describe how we have implemented portions of these specifications, as well as several enhancements, using TAO, which is our open-source real time CORBA ORB. Finally, we empirically evaluate the performance of TAO to illustrate how its features address the QoS requirements of certain types of real time applications.