Dtnmqtt: A Resilient Drop-In Solution for MQTT in Challenging Network Conditions

The usage of publish-subscribe protocols such as MQTT is common for industrial automation, smart cities, and environmental or agricultural monitoring. Due to challenging network conditions, this is either very expensive or sometimes not realistic to guarantee stable network links, which are usually required. Therefore, important sensor data is lost, or some applications are never even deployed for technical and financial reasons. When delays in message delivery are acceptable, the mobility of nodes and opportunistic communication can be used. We present a solution that acts as a drop-in replacement of MQTT and preserves its semantics without the need to rewrite existing applications. By mapping MQTT properties to the DTN Bundle Protocol, we minimize overhead and replicate application logic on the protocol level. Furthermore, we propose an extension of the TCP Convergence Layer standard, to minimize duplicate transmissions and ensure bundle-order as much as possible. Our evaluation shows significant advantages regarding message delivery rates in different scenarios compared to pure MQTT and mesh-based solutions, as well as the minimal resource footprint of our implementation.