Network softwarisation introduces flexibility in network management by enabling the deployment of network functions as software modules running on virtual machines. However, this creates new concerns for service availability and reliability due to multiple sources of failures at both software and hardware levels, potentially resulting in service degradations and penalties due to Service Level Agreement (SLA) violations. The survivability of critical services can best be guaranteed by pro-actively provisioning dedicated backup resources for these services, but at the cost of a high resource consumption. Aware of the divergent requirements of future services, a promising alternative is envisaged, allowing non-critical users to use the unused backup resources of high priority users. However, this approach poses a stringent challenge if a critical service disruption occurs, requiring the computation of a traffic rerouting solution for the non-critical requests when preempted from their borrowed resources. In this paper we first propose a generic multi-stage graph based algorithm as an alternative algorithm for Service Function Chain (SFC) deployments. Simulation results demonstrate that the proposed algorithm is optimized in terms of resource utilization, resulting in a 10% improvement in terms of acceptance ratio compared to a given state of the art algorithm, and within a 4% margin of the optimal solution. Based on the mentioned algorithm, we propose a new migration-aware algorithm for the mapping of non-critical services, enabling the non-critical services to borrow the unused backup resources from the critical services while minimizing the probability of preemption they could experience. The migration-aware algorithm results in more than an 8% resource saving, in most scenarios, compared to a dedicated backup strategy, and more than a 70% performance improvement in terms of the number of service preemptions, compared to a cost based algorithm. Additionally, whenever low priority users are preempted from their borrowed resources, we propose a new QoS-aware global-rerouting algorithm for remapping those users, reducing the impact of the service interruption thanks to avoiding the migration of surviving VNFs and virtual links when feasible. The proposed algorithm is shown to outperform a service restoration strategy based on local rerouting, in terms of successful service restoration and resource consumption.

网络软化通过支持将网络功能部署为在虚拟机上运行的软件模块，从而在网络管理中引入了灵活性。但是，由于软件和硬件级别上的多种故障源，这引起了对服务可用性和可靠性的新关注，这可能导致服务质量下降以及由于违反服务级别协议（SLA）而造成的损失。可以通过主动为这些服务预配置专用备份资源来确保关键服务的生存能力，但这要付出高昂的资源消耗。考虑到未来服务的不同需求，设想了一种有前途的替代方案，它允许非关键用户使用高优先级用户的未使用备份资源。然而，如果发生关键服务中断，这种方法将带来严峻的挑战，当非关键请求被抢占时，需要为非关键请求计算流量重新路由解决方案。在本文中，我们首先提出了一种基于多阶段图的通用算法，作为服务功能链（SFC）部署的替代算法。仿真结果表明，所提出的算法在资源利用方面进行了优化，与给定的现有技术相比，接收率提高了10％，并且在最佳解决方案的4％范围内。在上述算法的基础上，我们提出了一种新的迁移感知算法，用于非关键服务的映射，使非关键服务可以从关键服务中借用未使用的备份资源，同时最大程度地降低它们可能遭受的抢占的可能性。与专用备份策略相比，在大多数情况下，迁移感知算法可节省8％以上的资源，与基于成本的算法相比，在服务优先权方面，可将迁移性能提高70％以上。此外，每当低优先级用户从其借来的资源中被抢占时，我们都提出了一种新的QoS感知全局重路由算法，用于重新映射那些用户，从而在可行的情况下避免了幸存的VNF和虚拟链路的迁移，从而减少了服务中断的影响。结果表明，该算法优于基于本地路由的服务恢复策略，