NACK-Based Reliable Multicast Communication for Internet of Things Firmware Update

Abstract

The demand for efficient IoT firmware update protocols is increasing. Especially in scenarios with a large number of constrained devices, transferring a big amount of data, like a firmware image file, over a constraint network takes a long time to complete. During this time the functionality of the devices may be reduced. Therefore the firmware update is a critical use case for IoT. Multicast group communication can shorten the transmission time and use the network bandwidth efficiently. However, current IoT protocols using multicast cannot guarantee reliability which is most important for firmware file transmission. Furthermore existing solutions for reliable multicast cause a significant network overhead which can be prohibitive for a constrained IoT environment. To address these problems, we propose a reliable multicast solution employing a Negative ACK (NACK) mechanism that can be integrated with the Constraint Application Protocol (CoAP) widely used in IoT. Our protocol mitigates network congestion by reducing the number of packets that have to be sent while keeping the message size small making it a suitable solution even with a large number of devices. What is more, our proposal does not require an additional stack. In order to demonstrate the feasibility and effectiveness of our proposal, we carried out a real-world evaluation in a wireless mesh network testbed.