Architecture design for content-based publish-subscribe service networks has been a challenging problem, because its communication paradigm cannot be directly supported by existing network primitives. In this paper, we propose a new architectural design called MEDYM ñ Match Early with DYnamic Multicast. Unlike existing approaches, MEDYM does not rely on static overlay networks for event delivery. Instead, an event is matched against subscriptions early at the publishing server, to identify destinations with matching subscriptions, and then sent to destinations through a dynamically constructed multicast tree. This architecture achieves low computation cost in matching and high network efficiency in routing.

We evaluate MEDYM through detailed simulations, and compare it with the two major existing design approaches: Content-based Forwarding and Channelization. Results show that MEDYM significantly improves event delivery efficiency and system scalability. We also examine closely overheads introduced in MEDYM, and found them to be well acceptable and more than outweighed by the benefits of the approach. We expect the MEDYM architecture to scale to pub-sub networks of thousands of servers, which we believe is adequate for many interesting applications in the foreseeable future.