Efficient multistriding of large non-deterministic finite state automata for deep packet inspection

Multistride automata speed up input matching because each multistriding transformation halves the size of the input string, leading to a potential 2× speedup. However, up to now little effort has been spent in optimizing the building process of multistride automata, with the result that current algorithms cannot be applied to real-life, large automata such as the ones used in commercial IDSs, because the time and the memory space needed to create the new automaton quickly becomes unfeasible. In this paper, new algorithms for efficient building of multistride NFAs for packet inspection are presented, explaining how these new techniques can outperform the previous algorithms in terms of required time and memory usage.