Providing qos customization in distributed object systems

Abstract

Applications built on networked collections of computers are increasingly using distributed object platforms such as CORBA, Java RMI, and DCOM to standardize object interactions. With this increased use comes the increased need for enhanced Quality of Service (QoS) attributes related to fault tolerance, security, and timeliness. This paper describes an architecture called CQoS (Configurable QoS) for implementing such enhancements in a transparent, highly customizable, and portable manner. CQoS consists of two parts: application- and platform-dependent interceptors and generic QoS components. The generic QoS components are implemented using Cactus, a system for building highly configurable protocols and services in distributed systems. The CQoS architecture and the interfaces between the different components are described, together with implementations of QoS attributes using Cactus and interceptors for CORBA and Java RMI. Experimental results are given for a test application executing on a Linux cluster using Cactus/J, the Java implementation of Cactus. Compared with other approaches, CQoS emphasizes portability across different distributed object platforms, while the use of Cactus allows custom combinations of fault-tolerance, security and timeliness attributes to be realized on a per-object basis in a straightforward way.