RTT-based Congestion Control for the Internet of Things

The design of scalable and reliable transport protocols forIoT environments is still an unsolved issue. A simple stop-and-wait con-gestion control method and a lightweight reliability mechanism are onlyimplemented in CoAP, an application protocol that provides standard-ised RESTful services for IoT devices. Inspired by delay-based congestioncontrol algorithms that have been proposed for the TCP, in this work wepropose a rate control technique that leverages measurements of round-trip times (RTTs) to infer network state and to determine the ow ratethat would prevent network congestion. Our key idea is that the growthof RTT variance, coupled with thresholds on CoAP message losses, isan eective way to detect the onset of network congestion. To validateour approach, we conduct a comparative performance analysis with thetwo loss-based congestion control methods of standard CoAP under dif-ferent application scenarios. Results show that our solution outperformsthe alternative methods, with a signicant improvement of fairness androbustness against unacknowledged traffic.