Most softwarized telco services are conveniently framed as Service Function Chains (SFCs). Indeed, being structured as a combination of interconnected nodes, service chains may suffer from the single point of failure problem, meaning that an individual node malfunctioning could compromise the whole chain operation. To guarantee "highly available" (HA) levels, service providers are required to introduce redundancy strategies to achieve specific availability demands, where cost constraints have to be taken into account as well. Along these lines we propose HASFC (standing for High Availability SFC), a framework designed to support, through a dedicated REST interface, the MANO infrastructure in deploying SFCs with an optimal availability-cost trade off. Our framework is equipped with: i) an availability model builder aimed to construct probabilistic models of the SFC nodes in terms of failure and repair actions; ii) a chaining and selection module to compose the possible redundant SFCs, and extract the best candidates thereof. Beyond providing architectural details, we demonstrate the functionalities of HASFC through a use case which considers the IP Multimedia Subsystem, an SFC-like structure adopted to manage multimedia contents within 4G and 5G networks.

翻译：最软的调频器服务被方便地设计成服务功能链(SFCs ) 。 事实上,作为连接节点的组合结构,服务链可能受到单一故障问题的影响,这意味着单个节点故障会损害整个链条操作。为了保证“高可用”水平,服务供应商需要引入冗余战略,以实现具体的可用性需求,其中必须考虑到成本限制,并在此同时考虑成本限制。按照我们提议的这些方针,HASCC(为高可用性SFC)是一个框架,旨在通过专门的RET接口支持MANO基础设施部署具有最佳可得性成本交易的SFCs。我们的框架配备了:i)一个可用模型构建器,旨在构建SFC节点在故障和修理行动方面的概率模型;ii)一个链和选择模块,以构建可能的冗余 SFCs,并提取最佳候选人。除了提供建筑细节外,我们还通过一个考虑IP多介质子系统的使用案例,展示了HSFCFC的功能。一个类似于SFCS的结构,用于管理4G和5G网络内的多媒体内容。