Management and Control of Scalable and Resilient Next-Generation Optical Networks

Two research topics in next-generation optical networks with wavelength-division multiplexing (WDM) technologies were investigated: (1) scalability of network management and control, and (2) resilience/reliability of networks upon faults and attacks. In scalable network management, the scalability of management information for inter-domain light-path assessment was studied. The light-path assessment was formulated as a decision problem based on decision theory and probabilistic graphical models. It was found that partial information available can provide the desired performance, i.e., a small percentage of erroneous decisions can be traded off to achieve a large saving in the amount of management information. In network resilience under malicious attacks, the resilience of all-optical networks under in-band crosstalk attacks was investigated with probabilistic graphical models. Graphical models provide an explicit view of the spatial dependencies in attack propagation, as well as computationally efficient approaches, e.g., sum-product algorithm, for studying network resilience. With the proposed cross-layer model of attack propagation, key factors that affect the resilience of the network from the physical layer and the network layer were identified. In addition, analytical results on network resilience were obtained for typical topologies including ring, star, and mesh-torus networks. In network performance upon failures, traffic-based network reliability was systematically studied. First a uniform deterministic traffic at the network layer was adopted to analyze the impacts of network topology, failure dependency, and failure protection on network reliability. Then a random network layer traffic model with Poisson arrivals was applied to further investigate the effect of network layer traffic distributions on network reliability. Finally, asymptotic results of network reliability metrics with respect to arrival rate were obtained for typical network topologies under heavy load regime. The main contributions of the thesis include: (1) fundamental understandings of scalable management and resilience of next-generation optical networks with WDM technologies; and (2) the innovative application of probabilistic graphical models, an emerging approach in machine learning, to the research of communication networks.Ph.D.Committee Chair: Ji, Chuanyi; Committee Member: Chang, Gee-Kung; Committee Member: McLaughlin, Steven; Committee Member: Ralph, Stephen; Committee Member: Zegura, Elle

Disaster-Resilient Control Plane Design and Mapping in Software-Defined Networks

Communication networks, such as core optical networks, heavily depend on their physical infrastructure, and hence they are vulnerable to man-made disasters, such as Electromagnetic Pulse (EMP) or Weapons of Mass Destruction (WMD) attacks, as well as to natural disasters. Large-scale disasters may cause huge data loss and connectivity disruption in these networks. As our dependence on network services increases, the need for novel survivability methods to mitigate the effects of disasters on communication networks becomes a major concern. Software-Defined Networking (SDN), by centralizing control logic and separating it from physical equipment, facilitates network programmability and opens up new ways to design disaster-resilient networks. On the other hand, to fully exploit the potential of SDN, along with data-plane survivability, we also need to design the control plane to be resilient enough to survive network failures caused by disasters. Several distributed SDN controller architectures have been proposed to mitigate the risks of overload and failure, but they are optimized for limited faults without addressing the extent of large-scale disaster failures. For disaster resiliency of the control plane, we propose to design it as a virtual network, which can be solved using Virtual Network Mapping techniques. We select appropriate mapping of the controllers over the physical network such that the connectivity among the controllers (controller-to-controller) and between the switches to the controllers (switch-to-controllers) is not compromised by physical infrastructure failures caused by disasters. We formally model this disaster-aware control-plane design and mapping problem, and demonstrate a significant reduction in the disruption of controller-to-controller and switch-to-controller communication channels using our approach.Comment: 6 page

Network Reliability under Random Circular Cuts

Optical fiber networks consist of fibers that are laid out along physical terrestrial paths. As such, they are vulnerable to geographical physical failures, such as earthquakes and Electromagnetic Pulse (EMP) attacks. Moreover, such disasters can lead to multiple, geographically correlated, failures on the fiber network. Thus, the geographical layout of the fiber infrastructure has a critical impact on the robustness of the network in the face of such geographical physical failures. In this paper, we develop tools to analyze network connectivity after a `random' geographic disaster. The random location of the disaster allows us to model situations where the physical failures are not targeted attacks. In particular, we consider disasters that take the form of a `randomly' located disk in a plane. Using results from geometric probability, we are able to approximate some network performance metrics to such a disaster in polynomial time. We present some numerical results that make clear geographically correlated failures are fundamentally different from independent failures and then discuss network design in the context of random disk-cuts.National Science Foundation (U.S.) (Grant CNS-0830961)National Science Foundation (U.S.) (Grant CNS-1017800)United States. Defense Threat Reduction Agency (Grant HDTRA1-07-1-0004)United States. Defense Threat Reduction Agency (Grant HDTRA-09-1-005

Survivable and disaster- resilient submarine optical-fiber cable deployment

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Internete olan mevcut sosyal ve ekonomik bağlılık ve servis kesintileri nedeni ile oluşan önemli miktardaki tamir masrafları ile ağ kalımlılığı günümüzde telekomünikasyon ağ dizaynının önemli bir parçası olmuştur. Ayrıca, denizaltı fiber optik kabloların depremler gibi doğal afetlere veya insan-yapımı afetlere karşı zayıf olduğu da herkesçe kabul edilmiş bir gerçektir. Afete dayanıklı bir denizaltı kablo yerleştirilmesi, bir yada daha fazla kablo afet nedeni ile koptuğunda ağ servislerini yeniden eski haline getirmek için ağ operatörünün maliyetlerini (yolculuk maliyeti, kapasite kayıp maliyeti ve hasar gören kablonun tamir maliyeti) azaltabilir. Bu çalışmada afet-farkındalı denizaltı fiber optik kabloları yerleştirme problemini araştırdık. Kablolar için bir yol/rota seçerken yaklaşımımız toplam beklenen kayıp maliyetini, denizaltı fiber kabloların afetler nedeni ile zarar görebileceğini de düşünerek, bütçe ve diğer kısıtlamalar altında minimize etmeyi hedefler. Yaklaşımımızda afetle ilişkisiz arızaların ana kablonun yanında bir de yedek kablo sağlanarak üstesinden gelindiğini varsaydık. Önce basitçe bir su kütlesi (deniz/okyanus) tarafından ayrılmış iki kara parçası üzerine yerleştirilmiş iki düğümün olduğu bir senaryoyu düşündük. Daha sonra problemi formüle edebilmek için afet bölgelerinden sakınacak şekilde eliptik kablo şeklini dikkate aldık. En nihayetinde problem için, bu durumda yaklaşımımızın potansiyel faydalarını gösteren sayısal örneklerle desteklediğimiz bir Tamsayı Lineer Programlama formülasyonu ürettik. Bununla birlikte problemi daha pratik hale getirmek için, farklı kara parçalarına yerleşmiş çoklu düğümlerin örgüsel bir ağ topolojisini, düzenli şekillere sahip olmayan kabloları, deniz altındaki ortamın topografisini de dikkate aldık. Bu problemi de ifade etmek için sayısal örneklere birlikte bir Tamsayı Lineer Programlama sunduk. Sonuç olarak, pratik durumu düşünerek bir örnek durum incelemesi üzerinde yaklaşımımızı mevcut kablolama sistemleri ile kıyaslayarak teyit ettik. İki durumda da, sonuçlar bize %2-%11 oranında bir yerleştirme maliyeti artışı karşılığında beklenen maliyeti %90-%100 arasında azaltabileceğimizi gösterdi.With the existing profoundly social and economic reliance on the Internet and the significant reparation cost associated with service interruption, network survivability is an important element in telecommunication network design nowadays. Moreover, the fact that submarine optical-fiber cables are susceptible to man-made or natural disasters such as earthquakes is well recognized. A disaster-resilient submarine cable deployment can save cost incurred by network operators such as the capacity-loss cost, the cruising cost and the repair cost of the damaged cables, in order to restore network service when cables break due to a disaster. In this study, we investigate disaster-aware submarine fiber-optic cable deployment problem. While selecting a route/path for cables, our approach aims to minimize the total expected cost, considering that submarine optical-fiber cables may break because of natural disasters, subject to deployment budget and other constraints. In our approach, we assume disaster-unrelated failures are handled by providing a backup cable along with primary cable. In the simple case we consider a scenario with two nodes located on two different lands separated by a water body (sea/ocean). We then consider an elliptic cable shape to formulate the problem, which can be extended to other cable shapes, subject to avoiding deploying cable in disaster zones. Eventuaaly, we provide an Integer Linear Programming formulation for the problem supported with illustrative numerical examples that show the potential benefit of our approach. Furthermore, in order to make the problem more practical, we consider a mesh topology network with multiple nodes located on different sea/ocean, submarine optical- fiber cables of irregular shape, and the topography of undersea environment. Eventually, we provide an Integer Linear Programming to address the problem, together with illustrative numerical examples. Finally, we validate our approach by conducting a case study wherein we consider a practical submarine optical-fiber cable system susceptible to natural disasters. In this case, we compare our approach against the existing cable system in terms of deployment cost and reduction in expected cost. In either case results show that our approach can reduce expected cost from 90% to 100% at a slight increase of 2% to 11% in deployment cost of disaster-unaware approach