Towards Low Latency Software Routers

Network devices based on commodity hardware are capable of high-speed packet processing while maintaining the programmability and extensibility of software. Thus, software-based network devices, like software routers, software-based firewalls, or monitoring systems, constitute a cost-efficient and flexible alternative to expensive, special purpose hardware. The overall packet processing performance in resource-constrained nodes can be strongly increased through parallel processing based on off-theshelf multi-core processors. However, synchronization and coordination of parallel processing may counteract the corresponding network node performance. We describe how multi-core software routers can be optimized for real-time traffic by utilizing the technologies available in commodity hardware. Furthermore, we propose a low latency extension for the Linux NAPI. For the analysis, we use our approach for modeling resource contention in resource-constrained nodes which is also implemented as a resource-management extension module for ns-3. Based on that, we derive a QoSaware software router model which we use to evaluate our performance optimizations. Our case study shows that the different scheduling strategies of a software router have significant influence on the performance of handling realtime traffic.