Why Can Some Advanced Ethernet NICs Cause Packet Reordering?

The Intel Ethernet Flow Director is an advanced network interface card (NIC) technology. It provides the benefits of parallel receive processing in multiprocessing environments and can automatically steer incoming network data to the same core on which its application process resides. However, our analysis and experiments show that Flow Director can cause packet reordering in multiprocessing environments. In this paper, we use a simplified model to analyze why Flow Director can cause packet reordering. Our experiments verify our analysis.