Increasing Memory Efficiency of Hash-Based Pattern Matching for High-Speed Networks

Increasing speed of network links continuously pushes up requirements on the performance of network security and monitoring systems, including their typical representative and its core function: an intrusion detection system (IDS) and pattern matching. To allow the operation of IDS applications like Snort and Suricata in networks supporting throughput of 100Gbps or even more, a recently proposed pre-filtering architecture approximates exact pattern matching using hash-based matching of short strings that represent a given set of patterns. This architecture can scale supported throughput by adjusting the number of parallel hash functions and on-chip memory blocks utilized in the implementation of a hash table. Since each hash function can address every memory block, scaling throughput also increases the total capacity of the hash table. Nevertheless, the original architecture utilizes the available capacity of the hash table inefficiently. We therefore propose three optimization techniques that either reduce the amount of information stored in the hash table or increase its achievable occupancy. Moreover, we also design modifications of the architecture that enable resource-efficient utilization of all three optimization techniques together in synergy. Compared to the original pre-filtering architecture, combined use of the proposed optimizations in the 100Gbps scenario increases the achievable capacity for short strings by three orders of magnitude. It also reduces the utilization of FPGA logic resources to only a third.