Energy-Efficient Service Function Orchestration in 5G Mobile Networks

近年来，网络服务和新应用的多样性不断增加，这些网络服务和新应用在带宽、吞吐量和延迟方面受到广泛的服务需求。由于能源成本和CO2排放的增加，网络和系统的能源效率变得日益受到关注。5G移动的网络被认为是下一代互联网，以满足多样化服务的不同需求，并减少电信基础设施和数据中心的碳排放。与当前网络中使用专用设备构建的网络功能不同，5G移动的网络中的网元被提供为虚拟网络功能（VNF，网络功能的软件实现），其以服务功能链（SFC）的形式弹性编排，以满足动态服务需求和能效目标。SFC编排可以通过两个步骤执行：（i）VNF链接，以定义网络功能被连接以形成SFC的顺序;（ii）SFC放置，以定义SFC如何被嵌入到物理网络中。5G的跨域差异化服务、网络动态性和不确定性等本质特征使得传统的链接方法和布局模型不适用于5G移动的服务。因此，大量的研究工作致力于解决SFC编排的研究挑战。现有的研究主要利用明显的相互VNF依赖性来执行VNF链接。然而，这样的方法不能确定端到端5G服务的所有涉及的VNF的全局排序。此外，它缩小了创建SFC的通道，目的是在物理网络中实例化时优化差异化服务和能效。此外，SFC布局已被认为是一个确定性的调度问题与完整的服务和网络信息被称为先验。然而，当应用于5G移动的网络时，由于例如时变用户移动性和动态网络管理的因素，网络资源和服务要求在运行时变化，因此存在额外的挑战。到目前为止，在5G移动的网络中的节能SFC编排，同时考虑最佳VNF链和动态服务需求和基底资源容量，还没有在现有文献中报道。本项目将研究VNF链和SFC放置，以便在5G移动的网络的背景下实现节能和主动的SFC编排。为了逐步解决这个具有挑战性的问题，我们的工作将集中在三个主要目标上：1）提出一个统一的VNF链框架，该框架可以集成VNF依赖性，差异化服务策略和能源效率目标，以有效地构建SFC; 2）制定一个前瞻性的模式，在证监会首次配售时考虑未来网络和服务的变化，在5G移动的网络中执行实际服务部署; 3）提出实时确定性模型以针对不可预见的变化执行SFC放置，目的是最小化由于服务需求违规而对网络性能的负面影响。在目标1中获得的对节能VNF链接框架的见解将被馈送到目标2和目标3中的SFC放置模型中。该项目中提出的研究是首个关于5G移动的网络中节能SFC编排的研究。从长远来看，本文的研究成果将有助于5G业务编排的理论和实践，为未来绿色5G移动的网络的发展铺平道路。

Recent years have witnessed an increasing diversity of network services and novel applications, which are subject to a wide spectrum of service requirements with respect to bandwidth, throughput, and latency. Energy-efficiency of networks and systems becomes a dramatically growing concern, due to both increasing energy cost and CO2 emission. 5G mobile networks are being recognised as the next-generation Internet to meet the varying needs of diversified services and to reduce the carbon emissions of telecom infrastructure and data centres. In contrast to the network functions built with dedicated equipment in the current network, network elements in 5G mobile networks are provided as Virtual Network Functions (VNF, software implementations of network functions), which are elastically orchestrated in the form of Service Function Chains (SFC) to meet dynamic service demands and energy-efficiency goals.The SFC orchestration can be performed in two steps: (i) VNF chaining, to define the order in which network functions are connected to form an SFC; (ii) SFC placement, to define how the SFC is embedded into the physical network. The essential features in 5G, such as cross-domain differentiated service and network dynamicity and uncertainty, have made traditional chaining methods and placement models inapplicable for 5G mobile services. Therefore, significant efforts have been devoted to tackling the research challenges of SFC orchestration.Existing studies have primarily leveraged obvious mutual VNF dependencies to perform VNF chaining. However, such a method cannot determine the global ordering for all involved VNFs of an end-to-end 5G service. Furthermore, it narrows the channel to create SFCs with the aim of optimising the differentiated services and energy-efficiency when being instantiated in a physical network. In addition, SFC placement has been considered as a deterministic scheduling problem with the complete service and network information known as a priori. However, when applied to 5G mobile networks, additional challenges are presented in that network resource and service requirements vary at runtime due to the factors of e.g. time-varying user mobility and dynamic network management. Until now, an energy-efficient SFC orchestration in 5G mobile networks, considering both optimal VNF chaining and dynamic service demands and substrate resource capacities, has not been reported in the existing literature.This project will investigate VNF chaining and SFC placement in order to achieve energy-efficient and proactive SFC orchestration in the context of 5G mobile networks. To tackle this challenging problem progressively, our work will be focused on three major objectives: 1) propose a uniform VNF chaining framework, that can integrate VNF dependencies, differentiated service policies, and energy-efficiency objectives, to efficiently construct SFCs; 2) develop a proactive model, considering future network and service variations at the initialisation of SFC placement, to perform practical service deployment in 5G mobile networks; 3) propose a real-time deterministic model to perform SFC placement for unforeseen variations with the aim of minimising the negative effects on network performance due to service demand violations. The insights into the energy-efficient VNF chaining framework obtained in Objective 1 will be fed into the SFC placement models in Objective 2 and Objective 3. The research proposed in this project is the first of its kind on the energy-efficient SFC orchestration in 5G mobile networks. In the long-term aim, the implications of this research will contribute to 5G service orchestration in both theoretical and practical sides and pave the way for future green 5G mobile networks.