FlowLever: Leverage Flow Director for Packet Dispatch Acceleration in NFV.

The efficiency of dispatching incoming network flow packets to the destination virtual network function (VNF) has been recognized as a key problem in network function virtualization (NFV) platforms. Recent hardware assisted packet dispatch systems tend to rely on expensive software-defined network (SDN) switches or SmartNICs to mitigate the dispatch performance bottleneck, commonly observed in traditional software dispatch systems. In this paper, we revisit a hardware Flow Director (FDir) feature commonly found on commercial off-the-shelf NICs and propose a FDir-based NFV system that greatly accelerates packet dispatch with a much lower total cost of ownership (TCO). FlowLever is carefully designed to resolve nontrivial challenges such as the lack of flow state monitoring in FDir, the limited flow classification schema, heavy flow cache reconfiguration overhead, and high VNF scaling costs. With our software-hardware codesigned dispatch system and newly proposed flow activeness detection and cache replacement mechanisms, our evaluation using real-world network traffic traces shows that FlowLever improves the throughput by 1.6x - 2.8x and costs only 0.2 ms - 0.6 ms for load balance during VNF scaling.