In NFV networks, service functions (SFs) can be deployed on virtual machines (VMs) across multiple domains and then form a service function chain (MSFC) for end-to-end network service provision. However, any software component in a VM-based MSFC must experience software aging issue after a long period of operation. This paper quantitatively investigates the capability of proactive rejuvenation techniques in reducing the damage of software aging on a VM-based MSFC. We develop a semi-Markov model to capture the behaviors of SFs, VMs and virtual machine monitors (VMMs) from software aging to recovery under the condition that failure times and recovery times follow general distributions. We derive the formulas for calculating the steady-state availability and reliability of the VM-based MSFC composed of multiple SFs running on VMs hosted by VMMs. Sensitivity analysis is also conducted to identify potential dependability bottlenecks.

翻译：在NFV网络中，服务功能可部署于跨多个域的虚拟机上，进而构成用于端到端网络服务提供的服务功能链。然而，基于虚拟机的服务功能链中的任何软件组件在长时间运行后都会经历软件老化问题。本文定量研究了主动修复技术在降低软件老化对虚拟化服务功能链损害方面的能力。我们构建了一个半马尔可夫模型，用于在故障时间和恢复时间服从一般分布的条件下，刻画服务功能、虚拟机及虚拟机监控器从软件老化到恢复的完整行为。推导了由虚拟机监控器托管的虚拟机上运行的多个服务功能构成的虚拟化服务功能链的稳态可用性和可靠性计算公式，并通过灵敏度分析识别潜在的可靠性瓶颈。