A component and communication model for push systems

We present a communication and component model for push systems. Surprisingly, despite the widespread use of many push services on the Internet, no such models exist. Our communication model contrasts push systems with client-server and event-based systems. Our component model provides a basis for comparison and evaluation of different push systems and their design alternatives. We compare several prominent push systems using our component model. The component model consists of producers and consumers, broadcasters and channels, and a transport system. We detail the concerns of each of these components. Finally, we discuss a number of open issues that challenge the widespread deployment of push or any other system on an Internet-wide scale. Payment models are the most important among these and are not adequately addressed by any existing system. We briefly present the payment approach in our Minstrel project.