Comparison of subscriber assignment methods on scalable distributed Pub/Sub systems

Scalable messaging methods for IoT services are needed to accommodate a vast number of devices. Skip Graph based topic based pub/sub (SG-TPS), which utilizes multiple brokers composing a structured overlay network, is one of the promising candidates. In SG-TPS, the distribution delay time is widely influenced by a way to assign subscribers to each broker. There are two possible approaches: the intensive assignment by which subscribers having a same topic are accommodated on a same broker, and the extensive assignment by which the subscribers are accommodated on different brokers as far as possible. In this paper, we formulate the difference of the distribution delay time between these two approaches, and discuss about the optimization of subscriber assignment.