As the "network of network", the Internet has been playing a central and crucial role in modern society, culture, knowledge, businesses and so on in a period of over two decades by supporting a wide variety of network technologies and applications. However, due to its popularity and multi-provider nature, the future development of the Internet is limited to simple incremental updates. To address this challenge, network virtualization has been propounded as a potential candidate to provide the essential basis for the future Internet architecture. Network virtualization is capable of providing an open and flexible networking environment in which service providers are allowed to dynamically compose multiple coexisting heterogeneous virtual networks on a shared substrate network. Such a flexible environment will foster the deployment of diversified services and applications. A major challenge in network virtualization area is the Virtual Network Embedding (VNE), which aims to statically or dynamically allocate virtual nodes and virtual links on substrate resources, physical nodes and paths. Making effective use of substrate resources requires high-efficient and survivable VNE techniques. The main contribution of this thesis is two high-performance p-Cycle-based survivable virtual network embedding approaches. These approaches take advantage of p-Cycle-based protection techniques that minimize the backup resources while providing a full VN protection scheme against link and node failures.

The Dual Failure Restorability (DFR) problems involve the design of network topology to be restorable in the event of single and dual failures scenarios. We developed new integer linear programming (ILP) models to optimally design mesh topology networks with various survivability schemes; span restoration, p-cycle, DSP and path restoration to achieve any specified level of dual failure restorability in the networks. The first variation of the ILP models applies specified dual failure restorability limit to each pair of spans in the network, and the second applies the limit to average dual failure restorability in the entire network. We used 137 test-case networks, consisting of four network families; 10-node, 12-node, 15-node, and 18-node network families. The results show that the capacity cost increases as the specified levels of dual failure restorability increases, and the relative increase in capacity cost in sparsely connected networks is much higher compare to densely connected networks. / Engineering Management

Thesis (Ph. D.)--Helsinki University of Technology, Applied Electronics Laboratory, 20-05. / Includes bibliographical references (p. 167-190). Also available online.

Thesis (Ph. D.)--Helsinki University of Technology, Applied Electronics Laboratory, 20-05. / Also available online.

<p>System integration, interoperability, just in time delivery, window of opportunity, and dust-to-dust optimization are all keywords of our computerized future. Survivability is an important concept that together with dependability and quality of service are key issues in the systems of the future, i.e. infrastructural systems, business applications, and everyday desktop applications. The importance of dependable systems and the widely spread usage of dependable system together with the complexity of those systems makes middleware and frameworks for survivability imperative to the system builder of the future. This thesis presents a simulation approach to investigate the effect on data survival when the defending system uses knowledge of the current situation to protect the data. The results show the importance of situation awareness to avoid wasting recourses. A number of characteristics of the situational information provided and how this information may be used to optimize the system.</p>

abstract: In recent years, service oriented computing (SOC) has become a widely accepted paradigm for the development of distributed applications such as web services, grid computing and cloud computing systems. In service-based systems (SBS), multiple service requests with specific performance requirements make services compete for system resources. IT service providers need to allocate resources to services so the performance requirements of customers can be satisfied. Workload and performance models are required for efficient resource management and service performance assurance in SBS. This dissertation develops two methods to understand and model the cause-effect relations of service-related activities with resources workload and service performance. Part one presents an empirical method that requires the collection of system dynamics data and the application of statistical analyses. The results show that the method is capable to: 1) uncover the impacts of services on resource workload and service performance, 2) identify interaction effects of multiple services running concurrently, 3) gain insights about resource and performance tradeoffs of services, and 4) build service workload and performance models. In part two, the empirical method is used to investigate the impacts of services, security mechanisms and cyber attacks on resources workload and service performance. The information obtained is used to: 1) uncover interaction effects of services, security mechanisms and cyber attacks, 2) identify tradeoffs within limits of system resources, and 3) develop general/specific strategies for system survivability. Finally, part three presents a framework based on the usage profiles of services competing for resources and the resource-sharing schemes. The framework is used to: 1) uncover the impacts of service parameters (e.g. arrival distribution, execution time distribution, priority, workload intensity, scheduling algorithm) on workload and performance, and 2) build service workload and performance models at individual resources. The estimates obtained from service workload and performance models at individual resources can be aggregated to obtain overall estimates of services through multiple system resources. The workload and performance models of services obtained through both methods can be used for the efficient resource management and service performance assurance in SBS. / Dissertation/Thesis / Ph.D. Industrial Engineering 2012

System integration, interoperability, just in time delivery, window of opportunity, and dust-to-dust optimization are all keywords of our computerized future. Survivability is an important concept that together with dependability and quality of service are key issues in the systems of the future, i.e. infrastructural systems, business applications, and everyday desktop applications. The importance of dependable systems and the widely spread usage of dependable system together with the complexity of those systems makes middleware and frameworks for survivability imperative to the system builder of the future. This thesis presents a simulation approach to investigate the effect on data survival when the defending system uses knowledge of the current situation to protect the data. The results show the importance of situation awareness to avoid wasting recourses. A number of characteristics of the situational information provided and how this information may be used to optimize the system.

A key stage in the design-cycle of a military aircraft is the assessment of its vulnerability to hostile threat mechanisms. Such mechanisms inflict battle-damage to the aircraft structure and systems. This experimental investigation considered the aerodynamic consequences of simulated battle-damage to a two-dimensional wing. Key assumptions and techniques were identified leading to the modelling of both gunfire and missile fragmentation damage. Wind tunnel balance measurements were undertaken, together with surface pressure measurements and flow-visualisation methods. Force and moment results indicated extensive changes in coefficient values, whilst both smoke and surface visualisation paint successfully indicated the flow mechanisms present. Using these techniques the influences of damage and experimental variables were investigated, including damage type, size, location and Reynolds Number. Studies were also made into cases of multiple gunfire holes and the influence of internal wing construction. Results indicated that damage at quarter and half-chord locations gave greater coefficient changes than those seen for either leading or trailing edge damage. This was primarily due to reductions in the upper surface pressure peak due to through-flow. Such reductions were seen to extend in both a chordwise and spanwise direction. The flow mechanism identified indicated both similarities and differences to those of flat-plate jets in crossflows. Analysis of both gunfire and missile damage data lead to the development of a set of empirical relationships, which related damage location and size to coefficient changes.

This thesis discusses the development of a Numerical Wave Tank (NWT) capable of describing the coupled behaviour of Wave Energy Converters (WECs) and their moorings under extreme wave loading. The NWT utilises the open-source Computational Fluid Dynamics (CFD) software OpenFOAM(R) to solve the fully nonlinear, incompressible, Reynolds-Averaged Navier-Stokes (RANS) equations for air and water using the Finite Volume Method (FVM) and a Volume of Fluid (VOF) treatment of the interface. A method for numerically generating extreme waves is devised, based on the dispersively-focused NewWave theory and using the additional toolbox waves2Foam. A parametric study of the required mesh resolution shows that steeper waves require finer grids for mesh independence. Surface elevation results for wave-only cases closely match those from experiments, although an improved definition of the flow properties is required to generate very steep focused waves. Predictions of extreme wave run-up and pressure on the front of a fixed truncated cylinder compare well with physical measurements; the numerical solution successfully predicts the secondary loading cycle associated with the nonlinear ringing effect and shows a nonlinear relationship between incident crest height and horizontal load. With near perfect agreement during an extreme wave event, the reproduction of the six degree of freedom (6DOF) motion and load in the linearly-elastic mooring of a hemispherical-bottomed buoy significantly improves on similar studies from the literature. Uniquely, this study compares simulations of two existing WEC designs with scale-model tank tests. For the Wavestar machine, a point-absorber constrained to pitch motion only, results show good agreement with physical measurements of pressure, force and float motion in regular waves, although the solution in the wake region requires improvement. Adding bespoke functionality, a point-absorber designed by Seabased AB, consisting of a moored float and Power Take-Off (PTO) with limited stroke length, translator and endstop, is modelled in large regular waves. This represents a level of complexity not previously attempted in CFD and the 6DOF float motion and load in the mooring compare well with experiments. In conclusion, the computational tool developed here is capable of reliably predicting the behaviour of WEC systems during extreme wave events and, with some additional parameterisation, could be used to assess the survivability of WEC systems at full-scale before going to the expense of deployment at sea.

In traditional Wireless Sensor network's (WSN's), the sink is the only unconditionally trusted authority. If the sink is not connected to the nodes for a period of time then the network is considered as unattended. In Unattended Wireless Sensor Network (UWSN), a trusted mobile sink visits each node periodically to collect data. This network differs from the traditional multi hop wireless sensor networks where the nodes close to the sink deplete their power earlier than the other nodes. An UWSN can prolong the life time of the network by saving the battery of the nodes and also it can be deployed in environments where it is not practical for the sink to be online all the time. Saving data in the memory of the nodes for a long time causes security problems due to the lack of tamper-resistant hardware. Data collected by the nodes has to be secured until the next visit of the sink. Securing the data from an adversary in UWSN is a challenging task. We present two non-cryptographic algorithms (DS-PADV and DS-RADV) to ensure data survivability in mobile UWSN. The DS-PADV protects against proactive adversary which compromises nodes before identifying its target. DS-RADV makes the network secure against reactive adversary which compromises nodes after identifying the target. We also propose a data authentication scheme against a mobile adversary trying to modify the data. The proposed data authentication scheme uses inexpensive cryptographic primitives and few message exchanges. The proposed solutions are analyzed both mathematically and using simulations proving that the proposed solutions are better than the previous ones in terms of security and communication overhead.