Adaptive Development of Hash Functions in FPGA-Based Network Routers

Accelerated network technologies are crucial for implementing packet processing in high-speed computer networks and therefore, network routers accelerated by field-programmable gate arrays (FPGAs) are becoming common. One of the time-critical jobs in routers is packet classification which requires rapid lookup in tables. Fast hash computation is a must in order to process the packets in time. Adaptive development of hash functions is proposed in this paper. The hash functions are based on non-linear feedback shift registers and configured by an evolutionary algorithm. The hash functions are developed inside of an FPGA-based network router and fine-tuned for the given table content. The experiments on the problem of hashing Internet Protocol (IP) addresses demonstrate that the evolved simple hash functions provide faster hash computation, better memory resource utilization and require smaller chip area in comparison with conventional hash functions. The best conventional hash function was able to store by a couple of hundred less IP addresses in a 8k hash table, the computation of hashes was by 42% slower, and the implementation required 15-times more hardware area.