A Topic-Based Publish/Subscribe System in a Fog Computing Model for the IoT

In order to reduce the traffic of networks and servers in the IoT, types of the fog computing (FC) models are proposed, which are composed of fog nodes. A fog node supports application processes to calculate output data on sensor data and forward the output data to servers. A topic-based PS (publish/subscribe) model is a new contents-aware, event-driven model of a distributed system. Here, a process publishes a message whose contents are denoted by publication topics. A process specifies subscription topics and only is delivered messages whose publication topics include some of the subscription topics. In our previous studies, the MPSFC (Mobile PS (publish/subscribe) Fog Computing) model is proposed where mobile fog nodes like vehicles are interconnected and fog nodes communicate with one another in wireless networks by the PS model. In this paper, we propose a TBDT (Topic-based Data Transmission) protocol for mobile fog nodes to deliver messages to target nodes. In the evaluation, we show the number of messages in the TBDT protocol is fewer than the epidemic routing protocol while the delivery ratio is smaller.