Evaluation of the real-time properties of open-source protocol stacks

At present, two important trends in industrial environments are the adoption of Ethernet-based technologies to interconnect devices and the use of PCs provided with open-source real-time operating systems to execute control applications. This makes the implementation of distributed control systems easier and inexpensive. In these cases, it is of utmost importance that response times concerning the messages exchanged over the network be deterministically bounded. In this paper, the contribution to the end-to-end transmission delay which is due to the latencies introduced by the local protocol stack is analysed through experimental evaluation. In particular, two popular stacks have been taken into account, that is the one provided in conventional Linux and RTnet.