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 cannot guarantee in-order
packet delivery in multiprocessing environments. Packet reordering causes
various negative impacts. E.g., TCP performs poorly with severe packet
reordering. In this paper, we use a simplified model to analyze why Flow
Director can cause packet reordering. Our experiments verify our analysis