Failures in networks result in service disruptions which may cause deteriorated Quality of Service (QoS) for the end-users. Since SDN is becoming the mainstream paradigm for networks, implementation of a robust fault tolerance scheme for SDN-based networks is crucial. Existing SDN data plane fault tolerance approaches can be classified as reactive and proactive which may or may not rely on the controller, respectively. However, none of them qualifies as a complete solution, providing only partial remedies. In this work, we propose Dynamic Protection with Quality of Alternative Paths (DPQoAP) that considers not only the existing faults within the network but also the quality of alternative paths. As a result, we can sustain the QoS throughout the network after the recovery. We also investigate how application based parameters are affected by link failures. To this end, we explore the change in Quality of Experience (QoE) caused by link failures under different cases using Dynamic Adaptive Streaming over HTTP (DASH) for video streaming. On the other hand, even though DASH is proposed as a solution to improve the QoE affected by the dynamic conditions of the networks, it remains insufficient to handle the congested links that show the symptoms of a link failure. Thus, we apply the data plane fault tolerance approach in SDN to improve the QoE of DASH clients in the case of congestion as well as the failure. The performance of the proposed solutions is evaluated through various experiments considering the QoS and QoE parameters. It is observed that DPQoAP enhances the efficiency of the networking operations and adaptability of the applications.

网络故障会导致服务中断，这可能会导致最终用户的服务质量（QoS）下降。由于SDN成为网络的主流范例，因此为基于SDN的网络实施可靠的容错方案至关重要。现有的SDN数据平面容错方法可以分别分为反应式和主动式两种，分别可以依赖于控制器，也可以不依赖于控制器。但是，它们都没有资格作为一个完整的解决方案，仅提供了部分补救措施。在这项工作中，我们提出了具有备用路径质量的动态保护（DPQoAP），它不仅考虑了网络中现有的故障，还考虑了备用路径的质量。结果，我们可以在恢复后在整个网络上维持QoS。我们还将研究基于应用程序的参数如何受到链接故障的影响。为此，我们使用HTTP动态自适应流式传输（DASH）进行视频流传输，探索了在不同情况下由于链路故障导致的体验质量（QoE）的变化。另一方面，即使提出DASH作为改善受网络动态条件影响的QoE的解决方案，它仍然不足以处理显示链路故障症状的拥塞链路。因此，我们在SDN中应用数据平面容错方法来提高DASH客户端在拥塞和故障情况下的QoE。通过考虑QoS和QoE参数的各种实验来评估所提出解决方案的性能。