Network Function Virtualization (NFV) has been emerging as an appealing solution that transforms complex network functions from dedicated hardware implementations to software instances running in a virtualized environment. Due to the numerous advantages such as flexibility, efficiency, scalability, short deployment cycles, and service upgrade, NFV has been widely recognized as the next-generation network service provisioning paradigm. In NFV, the requested service is implemented by a sequence of Virtual Network Functions (VNF) that can run on generic servers by leveraging the virtualization technology. These VNFs are pitched with a predefined order through which data flows traverse, and it is also known as the Service Function Chaining (SFC). In this article, we provide an overview of recent advances of resource allocation in NFV. We generalize and analyze four representative resource allocation problems, namely, (1) the VNF Placement and Traffic Routing problem, (2) VNF Placement problem, (3) Traffic Routing problem in NFV, and (4) the VNF Redeployment and Consolidation problem. After that, we study the delay calculation models and VNF protection (availability) models in NFV resource allocation, which are two important Quality of Service (QoS) parameters. Subsequently, we classify and summarize the representative work for solving the generalized problems by considering various QoS parameters (e.g., cost, delay, reliability, and energy) and different scenarios (e.g., edge cloud, online provisioning, and distributed provisioning). Finally, we conclude our article with a short discussion on the state-of-the-art and emerging topics in the related fields, and highlight areas where we expect high potential for future research.

中文翻译：

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网络功能虚拟化中资源分配的新进展

网络功能虚拟化 (NFV) 已成为一种吸引人的解决方案，它将复杂的网络功能从专用硬件实现转变为在虚拟化环境中运行的软件实例。由于具有灵活性、效率、可扩展性、部署周期短、服务升级等诸多优势，NFV被广泛认为是下一代网络服务提供范式。在 NFV 中，请求的服务由一系列虚拟网络功能 (VNF) 实现，这些虚拟网络功能可以利用虚拟化技术在通用服务器上运行。这些 VNF 以预定义的顺序排列，数据流通过这些顺序遍历，也称为服务功能链 (SFC)。在本文中，我们概述了 NFV 中资源分配的最新进展。我们概括和分析了四个有代表性的资源分配问题，即（1）VNF 部署和流量路由问题，（2）VNF 部署问题，（3）NFV 中的流量路由问题，以及（4）VNF 重新部署和整合问题。之后，我们研究了 NFV 资源分配中的延迟计算模型和 VNF 保护（可用性）模型，这是两个重要的服务质量（QoS）参数。随后，我们通过考虑各种 QoS 参数（例如，成本、延迟、可靠性和能量）和不同的场景（例如，边缘云、在线供应和分布式供应）对解决广义问题的代表性工作进行了分类和总结。最后，我们以对相关领域的最新和新兴主题的简短讨论来结束我们的文章，