Abstract
The Constrained Application Protocol (CoAP) has been designed by the Internet Engineering Task Force (IETF) for Internet of Things (IoT) devices. Due to the limited radio channel capacities and hardware resources of such devices, congestion can be a serious problem. CoAP addresses this important issue with a basic congestion control mechanism. CoCoA, an Internet-Draft proposal, introduced alternative congestion control mechanisms for CoAP. Yet, there has been limited evaluation of these congestion control mechanisms in the literature. In this paper, we assess the methods applied in CoCoA in detail and propose improvements to address the shortcomings observed in the congestion control mechanisms. We carry out simulations to compare the congestion control performance for default CoAP, CoCoA, and our new proposal, CoCoA+, in a variety of network topologies and use cases. The results show that CoCoA+ outperforms default CoAP and achieves better results than CoCoA in the majority of considered cases.
Highlights
IPv6 capable networks of constrained devices play a crucial role in the effort of making the Internet of Things (IoT) [1] part of our everyday lives
The results showed that the limited congestion control (CC) capacities of default Constrained Application Protocol (CoAP) can be improved with Congestion Control/Advanced (CoCoA)
CoAP plays an important role in the ambit of constrained networks and the IoT, yet, so far only limited effort has been put into the evaluation of its CC mechanisms and into finding a suitable advanced CC mechanism
Summary
IPv6 capable networks of constrained devices play a crucial role in the effort of making the Internet of Things (IoT) [1] part of our everyday lives. The Internet Engineering Task Force (IETF) is developing specifications for different layers of the communication protocol stack that are trimmed to the requirements of networks of constrained, IPv6 capable devices. Amongst others, this resulted in the design of the IPv6 Routing Protocol for Low-Power and Lossy Networks. Preprint submitted to Elsevier (RPL) [2], the IPv6 over Low-Power Wireless Personal Area Network (6LoWPAN) adaptation layer [3], and the Constrained Application Protocol (CoAP) [4] These important standards have been adopted by entities such as the ZigBee Alliance [5] and Thread [6] to provide IPv6-capable communication protocol stacks for constrained devices in the IoT. Other standard protocol stacks for constrained devices that use IPv6 and 6LoWPAN are ISA 100.11a [7] and IEEE 1451.5 [8]
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