SDN-enabled Application-aware Network Control Architectures and their Performance Assessment (DFG SDN-App)Phase 2: Design and Evaluation of Flexible Programmable Hybrid Real-time Networks with Hard and Soft Real-time Guarantees

软件定义网络（SDN）标志着一个基本的范式转变，它允许在当今的通信网络中集成诸如应用程序感知资源管理之类的新概念。特别是，这些概念提高了面向用户的多媒体应用程序的体验质量（QoE）。该概念的可行性在DFG SDN-App的第一阶段得到了验证。第一阶段体系结构从两个方面研究了应用感知管理和控制的实现：在应用控制平面上考虑网络信息，提高了网络资源的利用率；严格考虑网络控制平面的应用需求，提高应用性能和QoE。因此，DFG SDN-App的第二阶段扩展了所考虑的场景和架构：除了照顾面向最终用户的多媒体应用程序和QoE（第一阶段）之外，它还集成了时间关键型（工业）服务及其不断变化的需求——最终用户不发挥主导作用的情况。特别是，第二阶段侧重于具有动态变化需求的时间关键服务的硬实时和软实时需求，如智能制造对控制设备的需求。硬实时约束要求，例如，最大端到端延迟和最大延迟抖动；软实时约束体现在随机保证中，例如丢包和延迟。现有的方法受到未使用的、因此浪费的网络资源或处理动态变化的需求和网络重新配置的复杂性的影响。实时约束是灵活性的交换。第二阶段的目标是从分析、仿真到测量和测试平台实现的方法，实现一个混合实时网络，为软硬实时应用提供保证，同时承载多媒体应用。特别对时间敏感网络（TSN）和网络可编程性（P4）等概念进行了研究和分析。为了评估整体体系结构，不仅采用传统的度量方法，还研究了网络灵活性等新度量方法，以量化在时间和成本约束下不断变化的需求下混合实时网络的效益。总体目标是针对选定用例（工业用例、数据中心用例、广域网用例）的指导方针，它结合了阶段1和阶段2的结果。第一阶段向工业和实时网络的扩展对于维持当今应用的动态和快速增长的需求非常重要。在面对重新配置时提供保证的灵活架构将允许实现可以同时承载所有应用程序类型的混合网络。由于能够为各种网络场景编程和使用标准硬件，网络运营商将在未来节省运营和资本支出。

Software Defined Networking (SDN) marks a fundamental paradigm shift that allows integrating new concepts such as application-aware resource management in today’s communication networks. Such concepts, in particular, improve the Quality-of-Experience (QoE) of user-oriented multimedia applications. The feasibility of such concept was demonstrated in Phase 1 of DFG SDN-App. The Phase 1 architecture investigated the realization of application-aware management and control on two fronts: taking network information on the application control plane into account improves the use of network resources; considering application demands on the network control plane rigorously improves application performance and QoE.Phase 2 of DFG SDN-App consequently extends the considered scenario and architecture: besides taking care of end user-oriented multimedia applications and QoE (Phase 1), it newly integrates time-critical (industrial) services and their changing requirements – cases where end users do not play a dominant role. In particular, Phase 2 focuses on hard as well as soft real-time requirements of time-critical services with dynamically changing demands like smart manufacturing to control devices. Hard real-time constraints require, e.g., a maximum end-to-delay and maximum delay jitter; soft real-time constraints manifest in stochastic guarantees, e.g., on packet loss and delay. Existing approaches suffer from unused, hence wasted network resources or the complexity to address dynamically changing demands and network reconfigurations. Real-time constraints are in trade-off to flexibility.Applying the methodologies from analysis, simulation, to measurement and testbed implementations, the goal of Phase 2 is to realize a hybrid real-time network that provides guarantees to hard and soft real-time applications, while at the same time hosting multimedia applications. In particular, concepts such as Time Sensitive Networking (TSN) and network programmability (P4) are investigated and analyzed jointly. To evaluate the overall architecture, not only traditional measures are applied, but also new measures such as network flexibility are investigated to quantify the benefits of hybrid real-time networks under changing demands with time and cost constraints. The overall target are guidelines for selected use cases (industrial, data center, wide area network), that combine the results of Phase 1 and 2.An extension of Phase 1 towards industrial and real-time networks is important to sustain the dynamically and faster growing demands of today’s applications. A flexible architecture that provides guarantees in face of reconfigurations will allow realizing hybrid networks that can host all application types simultaneously. With the ability to program and use standard hardware for all kind of network scenarios, network operators will save operation and capital expenditures in the future.