Building a Low Latency Linux Software Router

Packet processing (e.g. routing, switching, firewall) with commodity hardware is a cost-efficient and flexible alternative to specialized networking hardware. On commodity hardware the CPU typically becomes the bottleneck in packet processing. However, in well-known QoS mechanisms (e.g. DiffServ), the outgoing link is assumed to be the bottleneck. This limitation is unfavorable, in particular for latency-sensitive applications (e.g. VoIP, video conferencing, online gaming). Thus, we propose and implement a QoS concept for a Linux software router to prioritize latency-sensitive traffic at the incoming network interface. Our testbed measurements show that our prototype implementation improves the packet processing w.r.t the latency of latency-sensitive traffic even under high traffic loads.