Evaluating policies and mechanisms to support distributed real-time applications with CORBA

To be an effective platform for performance-sensitive real-time systems, co mmodity-off-the-shelf (COTS) distributed object computing (DOC) middleware must support application quality of service (QoS) requirements end-to-end. However, conventional COTS DOC middleware does not provide this support, wh ich makes it unsuited for applications with stringent latency, determinism, and priority preservation requirements. It is essential, therefore, to dev elop standards-based, COTS DOC middleware that permits the specification, a llocation. and enforcement of application QoS requirements end-to-end. The real-time CORBA and messaging specifications in the CORBA 2.4 standard are important steps towards defining standards-based, COTS DOC middleware t hat can deliver end-to-end QoS support at multiple levels in distributed an d embedded real-time systems. These specifications still lack sufficient de tail, however, to portably configure and control processor, communication, and memory resources for applications with stringent QoS requirements. This paper provides four contributions to research on real-time DOC middlew are, First, we illustrate how the CORBA 2.4 real-time and messaging specifi cations provide a starting point to address the needs of an important class of applications with stringent real-time requirements. Second, we illustra te how the CORBA 2.4 specifications are not sufficient to solve all the iss ues within this application domain. Third, we describe how we have implemen ted portions of these specifications, as well as several enhancements, usin g TAO, which is our open-source real-time CORBA ORE. Finally, we evaluate t he performance of TAO empirically to illustrate how its features address th e QoS requirements for certain classes of real-time applications, Copyright (C) 2001 John Wiley & Sons, Ltd.