Abstract
A logical chaining of Virtual Network Functions (VNFs) enables toy-blocking style composition of various network services. VNFs are generally based on Virtual Machines (VMs) running on commodity servers. However, such VM-based VNFs have poor packet forwarding performance because of the virtual network I/O overhead, and therefore virtualization of the core network functions can degrade overall network performance. In this paper, we propose a novel packet aggregation method (PA-Flow) that aggregates packets having a same next-hop VNF with no further latency. Unlike existing packet aggregation approaches, our method is effective for the virtual network I/O to reduce packet processing cost inside the host. Moreover, aggregated packets are further aggregated as going through the service chain, which drastically reduces traffic amount at the core network. We have implemented a PA-Flow module that works between a virtual switch and QEMU under the DPDK/vhost-user framework. PA-Flow showed 170% higher throughput than that of the default DPDK/vhost-user based system for a 2-VNF service chain. In addition, latency was also improved by about 2 us because of the packet amount reduction.