FastTSS: Accelerating tuple space search for fast packet classification in virtual SDN switches

The increasing tendency of network virtualization gives rise to extensive deployments of virtual switches in various virtualized platforms. However, virtual switches are encountered with severe performance bottlenecks with regards to their packet classification especially in the paradigm of Software-Defined Networking (SDN). This paper is thus motivated to design a fast packet classification scheme based on accelerated tuple space search, named as FastTSS, for virtual SDN switches. In particular, we devise a well-exploited cache with active exact flows to directly retrieve respective flow entries for most incoming packets, in virtue of the temporal locality of network traffic. Furthermore, we propose a novel hash algorithm to resolve the hash collisions of the cache, by providing three candidate locations for each inserted flow and making room for conflicting flow through kicking operation. As for the case of cache miss, we utilize the spatial locality of packet traffic to accelerate tuple space search, by dynamically sorting all tuples in terms of their reference frequencies and load factors. Eventually, we evaluate our designed packet classification scheme with physical network traffic traces by experiments. Extensive experimental results indicate that our designed FastTSS scheme outperforms the state-of-the-art ones with stable cache hit rates around 85% and the speedup of average search length up to 2.3, significantly promoting the packet classification performance of virtual SDN switches.