CoHaRT: A P2P-based deterministic transmission of large data amounts using CoAP

In Industrial Ethernet environments, usually only small amounts of data are transmitted. These transmissions must be deterministic to meet hard real-time requirements. But prospectively, also the deterministic transmission of high amounts of data and data streams is required. In this paper, a system based on the modified Peer-to-Peer network Kad called HaRTKad combined with the standardized protocol CoAP is presented to fulfill these requirements. The HaRTKad network bases on UDP. Because of the limited size of UDP packets, only small amounts of data can be transmitted and interpreted. Therefore, CoAP was chosen as protocol on top of HaRTKad. A highlight of CoAP is its applicability on constrained devices like embedded systems in automation environments. It has a very low overhead, high simplicity, and is very effective and well suited for the intended domain. CoAP enables the transmission and interpretation of big data amounts using the blockwise transfer. Thereby, HaRTKad ensures the deterministic data transmission of the packets. The combination of CoAP and HaRTKad is called CoHaRT. Besides the described concept of CoHaRT, real measurements from a running prototype are presented to demonstrate the performance of the data transmission.