Performance Comparison of UDP and TCP for Different CoAP Load Profiles

The Constrained Application Protocol (CoAP) is a popular lightweight protocol for managing IoT networks. The transport layer it operates on highly impacts its performance in Constrained-Node Networks. CoAP is originally designed as a lightweight web transfer protocol for Machine-to-Machine communication, using UDP as the underlying transport protocol. Recent studies argue the benefit of running CoAP over TCP as a measure for dealing with the increasing demand for enterprise infrastructure support when UDP-based traffic is limited, or firmware updates are sent. In this work, we experimentally evaluate the performance of CoAP over UDP and TCP within lossy networks. Our metrics include flow completion time as well as protocol overhead. The experimentation environment emulates the Narrowband-IoT, a 3GPP standardized network. We analyze two traffic types, periodic and bursty, and two connection lifespans, long and short. Results show that while CoAP over UDP performs better for short-lived connections, the TCP counterpart is more suitable for bursty traffic and long-lived connections. The different packet loss rates influence the performance by creating variations in flow completion time. For other scenarios, the trade-off we show between high performance and lower resource consumption must be considered for efficient deployments. With the help of our key findings, CoAP management can become more efficient.