A survey on OFDM-based elastic core optical networking

Orthogonal frequency-division multiplexing (OFDM) is a modulation technology that has been widely adopted in many new and emerging broadband wireless and wireline communication systems. Due to its capability to transmit a high-speed data stream using multiple spectral-overlapped lower-speed subcarriers, OFDM technology offers superior advantages of high spectrum efficiency, robustness against inter-carrier and inter-symbol interference, adaptability to server channel conditions, etc. In recent years, there have been intensive studies on optical OFDM (O-OFDM) transmission technologies, and it is considered a promising technology for future ultra-high-speed optical transmission. Based on O-OFDM technology, a novel elastic optical network architecture with immense flexibility and scalability in spectrum allocation and data rate accommodation could be built to support diverse services and the rapid growth of Internet traffic in the future. In this paper, we present a comprehensive survey on OFDM-based elastic optical network technologies, including basic principles of OFDM, O-OFDM technologies, the architectures of OFDM-based elastic core optical networks, and related key enabling technologies. The main advantages and issues of OFDM-based elastic core optical networks that are under research are also discussed

Network Virtualization Over Elastic Optical Networks: A Survey of Allocation Algorithms

Network virtualization has emerged as a paradigm for cloud computing services by providing key functionalities such as abstraction of network resources kept hidden to the cloud service user, isolation of different cloud computing applications, flexibility in terms of resources granularity, and on‐demand setup/teardown of service. In parallel, flex‐grid (also known as elastic) optical networks have become an alternative to deal with the constant traffic growth. These advances have triggered research on network virtualization over flex‐grid optical networks. Effort has been focused on the design of flexible and virtualized devices, on the definition of network architectures and on virtual network allocation algorithms. In this chapter, a survey on the virtual network allocation algorithms over flexible‐grid networks is presented. Proposals are classified according to a taxonomy made of three main categories: performance metrics, operation conditions and the type of service offered to users. Based on such classification, this work also identifies open research areas as multi‐objective optimization approaches, distributed architectures, meta‐heuristics, reconfiguration and protection mechanisms for virtual networks over elastic optical networks

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

Nature-inspired survivability: Prey-inspired survivability countermeasures for cloud computing security challenges

As cloud computing environments become complex, adversaries have become highly sophisticated and unpredictable. Moreover, they can easily increase attack power and persist longer before detection. Uncertain malicious actions, latent risks, Unobserved or Unobservable risks (UUURs) characterise this new threat domain. This thesis proposes prey-inspired survivability to address unpredictable security challenges borne out of UUURs. While survivability is a well-addressed phenomenon in non-extinct prey animals, applying prey survivability to cloud computing directly is challenging due to contradicting end goals. How to manage evolving survivability goals and requirements under contradicting environmental conditions adds to the challenges. To address these challenges, this thesis proposes a holistic taxonomy which integrate multiple and disparate perspectives of cloud security challenges. In addition, it proposes the TRIZ (Teorija Rezbenija Izobretatelskib Zadach) to derive prey-inspired solutions through resolving contradiction. First, it develops a 3-step process to facilitate interdomain transfer of concepts from nature to cloud. Moreover, TRIZ’s generic approach suggests specific solutions for cloud computing survivability. Then, the thesis presents the conceptual prey-inspired cloud computing survivability framework (Pi-CCSF), built upon TRIZ derived solutions. The framework run-time is pushed to the user-space to support evolving survivability design goals. Furthermore, a target-based decision-making technique (TBDM) is proposed to manage survivability decisions. To evaluate the prey-inspired survivability concept, Pi-CCSF simulator is developed and implemented. Evaluation results shows that escalating survivability actions improve the vitality of vulnerable and compromised virtual machines (VMs) by 5% and dramatically improve their overall survivability. Hypothesis testing conclusively supports the hypothesis that the escalation mechanisms can be applied to enhance the survivability of cloud computing systems. Numeric analysis of TBDM shows that by considering survivability preferences and attitudes (these directly impacts survivability actions), the TBDM method brings unpredictable survivability information closer to decision processes. This enables efficient execution of variable escalating survivability actions, which enables the Pi-CCSF’s decision system (DS) to focus upon decisions that achieve survivability outcomes under unpredictability imposed by UUUR