Overload Protection for CORBA Systems with Time Constraints

Scalable and reliable distributed object-oriented computing (DOC) middleware systems is an important technology in, for example, telecommunications service logic and distributed web servers. The Common Object Request Broker Architecture (CORBA), developed by the Object Management Group (OMG) is a speci cation of a common platform for DOC systems. CORBA acts as middleware, by inserting itself between the Operating System (OS) layer and the Application layer on a host. CORBA provides support for transparent interaction of objects situated on different nodes. The original CORBA specications had no support for timing constraints in applications and very little support in the terms of performance optimizations. Present extension to CORBA include support for real-time applications and a number of performance enhancements such as load balancing. However, no work so far address the issue of overload in a CORBA system. This paper presents a discussion of overload issues in distributed CORBA systems with time-constrained tasks. First a performance model of a CORBA system is introduced. Second, overload in distributed CORBA systems is discussed. Third, a number of classic overload protection mechanisms are applied to the performance model and investigated using simulation. The simulations show that even by using very simple protection mechanism, a good throughput can be achieved