Design, Implementation, and Evaluation of an Embedded CoAP Proxy Server for 6LoWPAN

Proxy servers are widely used in many contexts since they can enhance performance, security, and access control for production networks. The Constrained Application Protocol (CoAP), the de facto standard of Internet of Things (IoT) communications, specifies mechanisms and semantics to applications based on RESTful approach similar to HTTP. The CoAP standard defines an additional operation mode for proxying request, which is supported by several programming languages and platforms. However, there is no current implementation of a CoAP proxy for embedded systems, namely for devices supporting the Contiki-NG operating system. This paper discusses the design, implementation, and evaluation of a forward CoAP Proxy server for 6LoWPAN embedded systems with cache capabilities. We perform simulation and experimental evaluations with topologies involving up to three hops from the proxy to study performance in terms of response times and the number of exchanged packets. In simulation environments results show a 48.03%, 85.39%, and 134.21% in response time reduction at one, two, and three hops away. In experimental environments, results show that the use of our embedded CoAP Proxy server reduces response times in 7.46%, 30.67%, and 37.43% when requests are targeted to servers at one, two, and three hops away from the proxy respectively. In both scenarios, a reduction in the number of exchanged packets of 71.42%, 125%, and 166.66% for requests at each hop is achieved.