Distributed Load Balancing for the Resilient Publish/Subscribe Overlay in SeDAX

SEcure data-centric application eXtension (SeDAX) is a publish/subscribe information-centric networking architecture, where publishers send messages to the appropriate message broker over a Delaunay-triangulated overlay network. Resilient data forwarding and data redundancy enable a high level of reliability. Overlay nodes and topics are addressed via geo-coordinates. A topic is stored on primary and secondary nodes, those nodes closest and second-closest to the topic's coordinate, respectively. The overlay automatically reroutes a topic's messages to its secondary node should its primary node fail. In the original proposal, SeDAX determines the coordinate of a topic by hashing its name. This kind of topic allocation is static, which can lead to unintended load imbalances. We propose a topic delegation mechanism to make the assignment of topics to nodes dynamic. Our proposed mechanism is the only existing method to improve the flexibility and resource management of the SeDAX architecture so far. We define three resilience levels that allow information on the SeDAX overlay to survive 0, 1, or 2 node failures, imposing different loads on SeDAX nodes. For this elaborated SeDAX approach, we suggest a distributed resource management system that detects traffic imbalances among SeDAX nodes and re-assigns topics to other coordinates for load balancing purposes. We evaluate the load imbalance for the different resilience levels, for different topic characteristics, and in particular for topics with storage requirements growing over time. The proposed algorithm leads to well balanced load on SeDAX nodes while keeping load redistribution at a reasonable level.