Round-Trip Delay Estimation in OPC UA Server-Client Communication Channel

In this paper an estimation of round-trip delay (RTD) in OPC UA server-client channel was investigated in various data communication networks including Ethernet, WiFi, and 3G. Testing was carried out using the developed IoT gateway device running OPC UA server and remote computer running OPC UA client. The server and the client machines were configured to operate in Virtual Private Network powered by OpenVPN. Experimental analysis revealed that RTD values are distributed in the wide range exhibiting difficult-to-explain outliers significantly exceeding average RTD value. A preliminary exploration of the correlation between instantaneous load of communication gateway processor and RTD peaks was carried out on ARM Cortex A8 Texas instruments processors running at 600 MHz and 800 MHz clock frequency