Design and performance evaluation of congestion control mechanisms for the Constrained Application Protocol in the Internet Of Things

Nowadays the Internet of Things (IoT) is an emerging paradigm which calls for new challenges like transmission efficiency and protocols designed to operate on top of constrained devices. The Constrained Application Protocol (CoAP) is specifically designed to fulfil IoT requirements. Relying on UDP transport protocol, CoAP has to address the congestion control problem at the application level and it does in a very basic way. Recently a new congestion control mechanism for CoAP, called CoCoA+, has been proposed . Nowadays, CoCoA is currently under standardization within the activities of the CoRE Working Group. The aim of this work is to build and in-depth evaluation of CoAP and CoCoA+ congestion control mechanisms under a variety of traffic patterns and realistic IoT setups. The analysis revealed that CoCoA+ suffers of some shortcomings which could negatively impact on some performance metrics. Furthermore, a series of possible enhancements to alleviate, and possibly eliminate, such undesiderable behaviours are suggested and concretized in a proposed schema referred as Tower * algorithm. The proposed schema has been tested against CoCoA+ and CoAP under a variety of scenarios obtaining better results in terms of ratio between the number of retransmissions and number of CoAP transaction, which is translated into a reduced power consumption.Finally, the last part of this thesis introduces a new perspective on how to improve the congestion control mechanism for CoAP, by using a rate controlling mechanism with the aim of preventing congestion before it happens. The preliminary evaluation showed promising results, that have to be extensively evaluated in a future work