Congestion Control in Unicast and Multicast CoAP-based Communications

Lightweight devices and constrained resources used in the Internet of Things (IoT) applications have developed in exorbitant numbers, generating a large amount of data required for intelligent data processing. One of the foremost emerging messaging protocols used to address the requirements of these lightweight IoT nodes is Constrained Application Protocol (CoAP). Considering the unlimited number of messages and notifications generated by these devices, the problem of congestion occurs in CoAP communications. In this context, to fulfill successfully the need of transactions and succeed to handle reliably unicast and multicast communications, CoAP dispose of congestion control mechanisms to manage both unicast and multicast communications. The challenge addressed in this paper consists of designing appropriate congestion control mechanisms for CoAP that ensures a secure network operation while keeping the utilization of network resources efficiently. Therefore, in this paper, we shed the light on congestion control algorithms used to manage unicast and multicast communications CoAP based; we present a critical analysis of its performances and highlight some of its shortcomings and pitfalls. We combine and put forward two of our proposed adaptive algorithms of congestion control based on network conditions in both unicast and multicast communications.