Research And Implementation Of Topology Construction And Message Routing Of Openflow-Based Publish/Subscribe System

Distributed Event-Based Systems (DEBS) adopt Publish/Subscribe paradigm which decouples producers and consumers on space, time and control dimensions. Their decoupling feature improves the flexibility and scalability of distributed systems.When they are used in IoT (Internet of Things) scenarios, there are some problems to be considered such as wide-area topology maintenance and real-time event delivery to lots of event subscribers. For wide-area publish/subscribe systems, there are heterogeneous networks, computation nodes and applications, direct topology construction may result in data congestion in some local area or redundant data forwarding. Furthermore, the publish/subscribe systems over traditional networks can not completely satisfy the real-time requirement of event delivery for IoT applications. So migration from traditional Network to SDN is needed.We propose a data-localized topology maintenance scheme and a policy-driven name tree aggregation routing scheme to address the above issues. In IoT applications, the location of sensors and devices can often be predicted such that we can optimize the topology of Publish/Subscribe system. Besides, we also offer the design of policy-driven name tree to reduce the scale of routing tree, clusters generated by adjacent regions to enhance forwarding paths, and thus raise the efficiency of the whole system.The performance of Pub/Sub system is improved by measures above. But it does not completely satisfy the IoT applications’ requirements because it cannot control the process of underlying message forwarding in traditional networks. So we adopt Software Defined Network (SDN) as the underlying physical networks to support our solution. The switches/routers can be controlled by controllers over SDN which can work according to the applications’ requirements such that the real-time dispatching algorithm can be adopted.We do experiments to check the correctness and efficiency of our solution. The results show that our solution can promote the efficiency of Pub/Sub systems to support IoT applications.