1 Scalable Publish-Subscribe in a Managed Framework

Reliable multicast, publish-subscribe and group communication are highly effective in support of replication and event notification, and could serve as the enabling technologies for new types of applications that are both interac-tive and decentralized. To fully realize this vision, we need a high-performance, scalable, and reliable multicast en-gine as an integral part of the runtime environment. Since the majority of development today is done in managed, strongly-typed environments such as Java or.NET, integration with such environments is of particular importance. What factors limit performance and scalability of a reliable multicast engine in a managed environment? What sup-port from the runtime could improve performance, avoid instabilities, or make such systems easier to build? This paper sheds light on these questions by analyzing the performance of QuickSilver Scalable Multicast (QSM), a new multicast protocol and system built entirely in.NET. Memory-related overheads and scheduling-related phenomena are shown to dominate the behavior of our system. We discuss techniques that helped us alleviate some of these problems, and point to areas where better support from the runtime would be desirable