Evaluation and Optimization of Connectivity-Based Stability- and "Quality of Service"-Metrics in Overlay Networks

在网络工程中，在底层传输网络之上创建逻辑通信网络是一个公认的概念。它广泛应用于点对点网络、数据中心架构、虚拟专用网配置、wdm网络设计、智能电网以及未来互联网的多种愿景等应用场景。特别是，所有这些应用程序都以结构划分为底层（传输网络），覆盖（逻辑网络）和边缘映射为特征，为覆盖中的每个逻辑连接返回底层传输路径。由于它们在当今IT基础设施中不可或缺的作用，有必要采用抗故障和抗攻击的覆盖网络。然而，目前在覆盖网络中应用的结构优化更侧重于提高通信效率或为每个覆盖连接寻找本地备份路径。因此，去除或耗尽少量的底层边缘可以影响大量的覆盖连接。因此，覆盖层的服务质量和可用性参数可能会明显降低。确定这些关键结构和研究实际攻击方法是定性估计覆盖网络弹性的先决条件。此外，它们为优化提供了基础，因为识别出的弱点可以通过自适应覆盖结构或边缘映射来解决。然而，与经典网络相比，相关的图度量表现出本质上不同的性质。由于底层和覆盖连接之间的依赖关系，MaxFlow-MinCut定理不再有效。在经典网络中等价的图连通性度量可能不同。这将产生具有不同计算属性的多个可用的图连通性泛化。此外，覆盖层和底层之间的相互作用会影响与负载相关的服务质量参数，如流量、抖动和延迟。在存在不利的边缘映射的情况下，底层连接带宽的小偏差会导致覆盖层服务质量的显著下降。基于这些观察，提出的项目旨在最大限度地提高覆盖网络中基于连接的稳定性和服务质量措施。特别是应追求下列目标：覆盖场景下攻击者模型的研究与改进具有底层变化的覆盖网络中基于连通性的稳定性和服务质量度量分析方法的改进[j]。分析方法在代表性覆盖网络中的应用[j]。覆盖和边缘映射的稳定性优化

In network engineering, the creation of logical communication networks on top of underlying transport networks is a well-established concept. It is used in diverse application scenarios such as peer-to-peer networks, data center architectures, configuration of virtual private networks, the design of WDM-networks, the smart grid and in multiple visions of the future internet. In particular, all these applications feature a structural division into underlay (the transport network), overlay (the logical network) and an edge mapping, returning an underlay transport path for each logical connection in the overlay.Due to their indispensable role in present-day IT infrastructures, it is necessary to adopt overlay networks that are both failure- and attack-resistant. However, currently applied structural optimizations in overlay networks rather focus on improving communication efficiency or finding a local backup path for each overlay connection. Consequently, the removal or exhaustion of few underlay edges can effect a large number of overlay connections. Hence, the overlay's quality-of-service and availability parameters may decisively degrade.Determining such critical structures and studying realistic attack approaches are preconditions for the qualitative estimation of an overlay network's resiliency. Furthermore, they provide the basis for optimizations, since identified weaknesses may be resolved by an adaption of overlay structure or edge mapping.However, when compared with classical networks, the relevant graph measures exhibit substantially different properties. Due to dependencies between underlay and overlay connections, the MaxFlow-MinCut theorem is no longer valid. Measures of graph connectivity that are equivalent in classical networks may differ. This results in multiple available generalizations of graph connectivity, with different computational properties.Furthermore, the interactions between overlay and underlay affect load-dependent quality-of-service parameters, such as flow rates, jitter and delays. In the presence of a disadvantageous edge mapping, small deviations in the bandwidth of underlay connections can lead to considerable decrease in the overlay's quality-of-service.Based on these observation, the proposed project aims at the maximization of connectivity-based stability and quality-of-service measures in overlay networks. In particular, the following objectives shall be pursued:1. Investigation and refinement of attacker models in overlay scenarios2. Improvement of analysis methods of connectivity-based stability and quality-of-service measures in overlay networks with underlay changes3. Application of analysis methods on representative overlay networks4. Stability optimizations of overlay and edge mapping