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For many years the research community has attempted to model the Internet in order to better understand its behaviour and improve its performance. Since much of the structural complexity of the Inter- net is due to its multilevel operation, the Internet's multilevel nature is an important and non-trivial feature that researchers must consider when developing appropriate models. In this paper, we compare the normalised Laplacian spectra of physical-and logical-level topologies of four commercial ISPs and two research networks against the US freeway topology, and show analytically that physical level communication networks are structurally similar to the US freeway topology. We also generate synthetic Gabriel graphs of physical topologies and show that while these synthetic topologies capture the grid-like structure of actual topologies, they are more expensive than the actual physical level topologies based on a network cost model. Moreover, we introduce a distinction between geographic graphs that include degree-2 nodes needed to capture the geographic paths along which physical links follow, and structural graphs that eliminate these degree-2 nodes and capture only the interconnection properties of the physical graph and its multilevel relationship to logical graph overlays. Furthermore, we develop a multilevel graph evaluation framework and analyse the resilience of single and multilevel graphs using the flow robustness metric. We then confirm that dynamic routing performed over the lower levels helps to improve the performance of a higher level service, and that adaptive challenges more severely impact the performance of the higher levels than non-adaptive challenges.

Communication networks have evolved tremendously over the past several decades, offering a multitude of services while becoming an essential critical infrastructure in our daily lives. Networks in general, and the Internet in particular face a number of challenges to normal operation, including attacks and large-scale disasters, as well as due to the characteristics of the mobile wireless communication environment. It is therefore vital to have a framework and methodology for understanding the impact of challenges to harden current networks and improve the design of future networks. In this paper, we present a framework to evaluate network dependability and performability in the face of challenges. This framework uses ns-3 simulation as the methodology for analysis of the effects of perturbations to normal operation of the networks, with a challenge specification applied to the network topology. This framework can simulate both static and dynamic challenges based on the failure or wireless-impairment of individual components, as well as modelling geographically-correlated failures. We demonstrate this framework with the Sprint Rocketfuel and synthetically generated topologies as well as a wireless example, to show that this framework can provide valuable insight for the analysis and design of resilient networks.

As the Internet becomes increasingly important to all aspects of society, the consequences of disruption become increasingly severe. Thus it is critical to increase the resilience and survivability of the future network. We define resilience as the ability of the network to provide desired service even when challenged by attacks, large-scale disasters, and other failures. This paper describes a comprehensive methodology to evaluate network resilience using a combination of analytical and simulation techniques with the goal of improving the resilience and survivability of the Future Internet.