Hybrid Regular Expression Matching for Deep Packet Inspection on Multi-Core Architecture

Many network security applications in today´s networks are based on deep packet inspection, checking not only the header portion but also the payload portion of a packet. For example, traffic monitoring, layer-7 filtering, and network intrusion detection all require an accurate analysis of packet content in search for predefined patterns to identify specific classes of applications, viruses, attack signatures, etc. Regular expressions are often used to represent such patterns. They are implemented using finite automata, which take the payload of a packet as an input string. However, existing approaches, both non-deterministic finite automata (NFA) and deterministic finite automata (DFA), have limitations; NFAs have excessive time complexity while DFAs have excessive space complexity. In this paper, we propose an efficient algorithm for regular expression matching to implement deep packet inspection on multi-core architecture. A regular expression is split into NFA-friendly components and DFA-friendly components, which are then assigned to different cores. This hybrid method combines the merits of NFA and DFA implementations, and efficiently takes advantage of multi-core architecture. We evaluate our algorithm using rule sets provided by Snort, a popular open-source intrusion detection system. The simulation results show that our approach outperforms existing NFA/DFA and hybrid approaches. Furthermore, our algorithm performs well on the important issues on multi-core architecture design, such as load balancing, data locality and communication between cores.