An FPGA-based In-NIC Cache Approach for Lazy Learning Outlier Filtering

As data sets grow rapidly in size and the number, an outlier detection that filters unnecessary normal information becomes important. In this paper, we propose to move the outlier detection from an application layer to a NIC (Network Interface Card). Only anomalous items or events are delivered for a network protocol stack and the other packets are discarded at the NIC. The demands for storage and computation costs at a host are thus drastically reduced. We employ lazy learning algorithms for the outlier detection, because they can be applied to complex reference data including different clusters. However, it is challenging to offload the lazy learning to NIC hardware because of high computational cost and huge reference data. In this paper, we propose to cache only a frequently-accessed portion of reference data in the NIC. This idea can be applied to lazy learning algorithms in general. LOF (Local Outlier Factor) and KNN (K-Nearest Neighbor) are thus implemented on an FPGA (Field Programmable Gate Arrays) based NIC. Simulation results of the proposed system using LOF with 100,000 reference data show that 45% to 90% of queries are hit to the proposed cache and filtered at the NIC. The results are corresponding to 1.82x to 10x throughput improvements on the outlier filtering compared to that of a software-based execution.