Enabling Flexible QoS Support in the Object Request Broker COOL

Support of end-to-end Quality-of-Service (QoS) and appropriate high-level programming abstractions are two crucial factors for the development of future telecommunication services and distributed multimedia systems. Todays middleware systems, like the Common Object Request Broker Architecture (CORBA), support high-level programming abstractions, but they do not appropriately support the demands from soft realtime and multimedia applications. We develop a flexible and adaptable middleware that supports a broad range of QoS requirements of distributed multimedia applications. In this paper, we present design, implementation, and preliminary performance evaluation of our first prototype. We have extended the object and message layer of the CORBA implementation COOL with QoS support by (1) enabling QoS specifications for method invocations, (2) integrating bilateral QoS negotiation between client and server, and (3) implementing a simple unilateral QoS negotiation between message layer and transport layer in the Object Request Broker (ORB). In the transport layer of COOL, we have integrated Da CaPo to flexibly support the various QoS requirements. Our work demonstrates that it is possible to support QoS with minor changes in GIOP and the use of a QoS supporting transport protocol.