# The Effects of High-Performance Cloud System for Network Function Virtualization
## 1 Introduction  
In 2012, the European Telecommunications Standards Institute (ETSI) launched an industry working group to comply with the Network Function Virtualization (NFV) framework and standardization [1]. The primary goal of NFV technologies is to decouple network functions from the dedicated hardware to be run on commodity servers as software. With the help of NFV, telecom operators exploit commercial off-the-shelf servers and virtualization technologies to provide a variety of network functions. Therefore, telecom operators reduce capital expenditure while improving flexibility from the benefits of NFV technologies [2]. Cloud computing also provides scalability and availability for NFV services to be more reliable in business operations [3, 4]. These advantages are attractive for telecom operators towards NFV on the cloud. OpenStack, an open-source cloud operation system, plays a critical role in network function virtualization infrastructure (NFVI) and virtualized infrastructure managers (VIM) [5] of the ETSI framework. Telecom operators build an on-premises cloud on multiple nodes and deploy virtual network functions (VNFs) on top of the NFVI. However, the network functions in virtual machines (VMs) require a hypervisor or virtual machine manager (VMM) to mediate available virtual and physical resources. This extra layer brings challenges to the performance degradation of VNFs [6] on a cloud system. The performance on computation and networking is dramatically reduced without any improvement. Many works attempt to improve the efficiency of virtual resources on the cloud from different perspectives. The workflow scheduling problem is addressed in [7, 8, 9] toimprove the workload execution on the cloud system. The authors of [10; 11; 12; 13; 14] focus on VM placement to improve the power consumption for the cloud system. Some works [15; 16; 17; 18; 19] further take the load-balancing issue into consideration for better resource utilization in VNF placement. Previous works have proposed effective mechanisms and algorithms to improve the resource management of VNF on the cloud. However, rare works emphasize performance enhancement techniques from scratch for system virtualization. Intel Corp. devotes massive efforts to enhanced platform awareness (EPA) [20] for virtualization technologies. The bottlenecks of computation performance are enhanced by CPU pinning for allocating dedicated CPU cores to a virtual machine (VM), and hugepages for improving effective memory access. A practical cloud system with enhanced technologies for computation has been preliminarily verified in [21]. For the enhancement of network performance, Open vSwitch with DPDK (OVS-DPDK) and single root I/O virtualization (SR-IOV) are two effective technologies to overcome the communication bottleneck. However, most of the previous works mainly focus on the perspective of network devices [22; 23; 24; 25] rather than a comprehensive verification of the overall cloud system under test (SUT). In addition, a telecom service usually requires chaining of network functions, named the service function chain (SFC) [26], to serve the NFV application. The length of a service chain has an impact on network performance. When the path of a service chain contains only one VNF on the cloud system, the packets are sent from a traffic generator to the target VNF via a physical network interface controller (NIC). The packets are then transmitted back to the traffic generator through a physical top-of-rack (TOR) switch. This communication scenario is called a physical-virtual-physical (PVP) flow. If the SFC is compounded by two VNFs, the packets are sent from a traffic generator to one VNF and forwarded to another VNF before transmitting back to the traffic generator. This scenario is a typical physical-virtual-virtual-physical (PVVP) flow. When the service path becomes longer, the workload of components in this path is heavier. Thus, the performance is deteriorated, but less attention has been paid to this in the literature.