A Middleware Service for Real-Time Push-Pull Communications

Current and emerging real-time and multimedia applications like multi-party collaboration, internet telephony and distributed command control systems require the exchange of information over distributed and heterogeneous nodes. Multiple data types including voice, video, sensor data, real-time intelligence data and text are being transported widely across today's information, control and surveillance networks. All such applications can beneet enormously from middleware, operating system and networking services that can support QoS guarantees, high availability, dynamic reconngurability and scalability. In this paper, we propose a middleware layer called a \Real-Time Push-Pull Communications Service" to easily and quickly disseminate real-time information across heterogeneous nodes. Push-Pull Communications is an extension of the real-time publisher/subscriber model 4], and represents both \push" (data transfer initiated by a sender) and \pull" (data transfer initiated by a receiver) communications. Nodes with widely diiering processing power and networking bandwidth can coordinate and co-exist by the provision of appropriate and automatic support for transformation on data and supports scaling. Diierent information sources and sinks can operate at diierent frequencies and also can choose another (intermediate) node to act as their proxy and and deliver data at the desired frequency. This service has been implemented on RT-Mach, a resource-centric kernel using resource kernel primitives 7]. This paper presents an overview of the design, implementation and preliminary performance evaluation of the model.