Delay-Aware Application Protocol for Internet of Things

Existing CoAP primarily focuses on communication (i.e., client/server-based request/response interaction) between constrained devices in a constrained network. Constrained networks may have large latencies and constrained devices may not be able to respond in a timely manner. Therefore, incorporating delay awareness in the CoAP protocol may prove beneficial for communications between devices. This article presents a new method to support a delay-aware CoAP messaging model, where a DelayIndicator is proposed to be contained in messages to reflect delay tolerance information. Furthermore, the DelayIndicator can be leveraged by CoAP Clients and CoAP Servers to improve their operations of entering sleep mode to save energy while not violating delay tolerances. With this new enabler, a timeout mechanism for CoAP Responses is put forward to enhance CoAP performance. Simulation results show that incorporating delay awareness in CoAP significantly improves messaging performance.