Egemen K. Çetinkaya

Resilience and survivability in communication networks: Strategies, principles, and survey of disciplines

The Internet has become essential to all aspects of modern life, and thus the consequences of network disruption have become increasingly severe. It is widely recognised that the Internet is not sufficiently resilient, survivable, and dependable, and that significant research, development, and engineering is necessary to improve the situation. This paper provides an architectural framework for resilience and survivability in communication networks and provides a survey of the disciplines that resilience encompasses, along with significant past failures of the network infrastructure. A resilience strategy is presented to defend against, detect, and remediate challenges, a set of principles for designing resilient networks is presented, and techniques are described to analyse network resilience.

Evaluation of network resilience, survivability, and disruption tolerance: analysis, topology generation, simulation, and experimentation

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 future networks. 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 topology generation, analytical, simulation, and experimental emulation techniques with the goal of improving the resilience and survivability of the Future Internet.

Highly-Dynamic Cross-Layered Aeronautical Network Architecture

Highly-dynamic wireless environments present unique challenges to end-to-end communication networks, caused by the time-varying connectivity of high-velocity nodes combined with the unreliability of the wireless communication channel. Such conditions are found in a variety of networks, including those used for tactical communications and aeronautical telemetry. Addressing these challenges requires the design of new protocols and mechanisms specific to this environment. We present a new domain-specific architecture and protocol suite, including cross-layer optimizations between the physical, MAC, network, and transport layers. This provides selectable reliability for multiple applications within highly mobile tactical airborne networks. Our contributions for this environment include the transmission control protocol (TCP)-friendly transport protocol, AeroTP; the IP-compatible network layer, AeroNP; and the geolocation aware routing protocol AeroRP. Through simulations we show significant performance improvement over the traditional TCP/IP/MANET protocol stack.

A geographical routing protocol for highly-dynamic aeronautical networks

Emerging networked systems require domain-specific routing protocols to cope with the challenges faced by the aeronautical environment. We present a geographic routing protocol AeroRP for multihop routing in highly dynamic MANETs. The AeroRP algorithm uses velocity-based heuristics to deliver the packets to destinations in a multi-Mach speed environment. Furthermore, we present the decision metrics used to forward the packets by the various AeroRP operational modes. The analysis of the ns-3 simulations shows AeroRP has several advantages over other MANET routing protocols in terms of PDR, accuracy, delay, and overhead. Moreover, AeroRP offers performance tradeoffs in the form of different AeroRP modes.

AeroRP performance in highly-dynamic airborne networks using 3D Gauss-Markov mobility model

Emerging airborne networks require domainspecific routing protocols to cope with the challenges faced by the highly-dynamic aeronautical environment. We present an ns-3 based performance comparison of the AeroRP protocol with conventional MANET routing protocols. To simulate a highly-dynamic airborne network, accurate mobility models are needed for the physical movement of nodes. The fundamental problem with many synthetic mobility models is their random, memoryless behavior. Airborne ad hoc networks require a flexible memory-based 3-dimensional mobility model. Therefore, we have implemented a 3-dimensional Gauss-Markov mobility model in ns-3 that appears to be more realistic than memoryless models such as random waypoint and random walk. Using this model, we are able to simulate the airborne networking environment with greater realism than was previously possible and show that AeroRP has several advantages over other MANET routing protocols.

Multilevel resilience analysis of transportation and communication networks

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 Internet 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.

Modelling and analysis of network resilience

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.

A comprehensive framework to simulate network attacks and 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.

Redundancy, diversity, and connectivity to achieve multilevel network resilience, survivability, and disruption tolerance invited paper

Communication networks are constructed as a multilevel stack of infrastructure, protocols, and mechanisms: links and nodes, topology, routing paths, interconnected realms (ASs), end-to-end transport, and application interaction. The resilience of each one of these levels provides a foundation for the next level to achieve an overall goal of a resilient, survivable, disruption-tolerant, and dependable Future Internet. This paper concentrates on three critical resilience disciplines and the corresponding mechanisms to achieve multilevel resilience: redundancy for fault tolerance, diversity for survivability, and connectivity for disruption tolerance. Cross-layering and the mechanisms at each level are described, including richly connected topologies, multipath diverse routing, and disruption-tolerant end-to-end transport.

Topology connectivity analysis of internet infrastructure using graph spectra

Understanding and modelling the Internet has been a major research challenge in part due to the complexity of the interaction among its protocols and in part due to multilevel, multidomain topological structure. It is therefore crucial to properly analyse each structural level of the Internet to gain a better understanding, as well as to improve its resilience properties. In this paper, first we present the physical and logical topologies of two ISPs and compare these topologies with the US interstate highway topology by using graph metrics and then using the normalised Laplacian spectrum. Our results indicate that physical network topologies are closely correlated with the motorway transportation topology. Finally, we study the spectral properties of various communication networks and observe that the spectral radius of the normalised Laplacian matrix is a good indicator of graph connectivity when comparing different size and order graphs.