On TCP Throughput Pathology in CPU-Bound Communication over Automotive Ethernet

TCP protocol optimized for the general Internet environment can fail to maximally realize its potential in the in-vehicular network environment such as the automotive Ethernet. In this paper, we demonstrate that a throughput pathology can develop in the TCP communication between two ECUs that are typically lower-speed machines. We find that it stems from how the processing power is divided between the TCP kernel packet processing and the sending application at the TCP sender side. Moreover, once it sets in, it persistently decreases the TCP throughput by few tens of megabits per second (Mbps) over an extended period of time. Through kernel profiling and TCP code analysis, we prescribe a remedy that solves the pathology and enables ECUs to fully materialize the maximum throughput.