In communication networks today, the amount of users and traffic is constantly increasing. This results in the need for upgrading the networks to handle the demand. Free space optics is a technique which is relatively cheap with high capacity compared to most systems today. On the other hand, FSO have some disadvantages with the effects on the system by, for instance, turbulence and weather. The aim of the project is to investigate the use of network optimization for designing an optimal network in terms of capacity and cost. Routing optimization is also covered in terms of singlepath and multipath routing. To mitigate the problem with turbulence affecting the system network survivability is implemented with both proactive and reactive solutions. The method used is to implement the system in Matlab, the system should also be tested so that it works as intended. The report covers related work as well as theory behind FSO and the chosen optimization algorithms. The system uses modified Bellman-Ford optimization as well as Kruskal’s minimum spanning tree. K-link-connectivity is also implemented for the network survivability and multipath algorithm. Results of the implementation shows that the network survivability improves the robustness of the system by changing paths for traffic which is affected by broken links. Routing done by multipath will increase the throughput and also reduce the delay for the traffic.

In communication networks today, the amount of users and traffic is constantly increasing. This results in the need for upgrading the networks to handle the demand. Free space optics, FSO, is a technique which is relatively cheap with high capacity compared to most systems today. On the other hand, FSO have some disadvantages with the effects on the system by, for instance, turbulence and weather. The aim of the project is to investigate the use of network optimization for designing an optimal network in terms of capacity and cost. Routing optimization is also covered in terms of singlepath and multipath routing. To mitigate the problem with turbulence affecting the system network survivability is implemented with both proactive and reactive solutions. The method used is to implement the system in Matlab, the system should also be tested so that it works as intended. The report covers related work as well as theory behind FSO and the chosen optimization algorithms. The system uses modified Bellman-Ford optimization as well as Kruskal’s minimum spanning tree. K-link-connectivity is also implemented for the network survivability and multipath algorithm. Results of the implementation shows that the network survivability improves the robustness of the system by changing paths for traffic which is affected by broken links. Routing done by multipath will increase the throughput and also reduce the delay for the traffic.

The 3GPP Long Term Evolution (LTE) is considered as a dominant future cellular wireless technology in terms of performance and user experience. With technological advancement of the wireless networks, dependencies and business impact of the mobile network services have increased phenomenally. It is, therefore, crucial to address the issues regarding network infrastructure or service failure. In this thesis, a self-healing solution is presented for the LTE Evolved Packet Core (EPC) with a view to maintaining service continuity in the event of core network elements - the MME and S-GW failures. The core network element failures have significant impact on a larger number of subscribers in comparison to the access network element failures. In the proposed self-healing scheme, the restoration mechanisms and associate failover recovery procedures with regards to service survivability are described in details from the LTE network and protocol perspective. This thesis studies two different self-healing approaches - the centralized active-backup and distributed active-active and conducts simulation for each approach in various failure scenarios. The performances of each of these scenarios are evaluated in terms of service restoration time, throughput, EPS (Evolved Packet System) bearer delay etc. The results show that the proposed self-healing system can ensure service continuity at a certain level if resources are properly provisioned. And in terms of restoration delay, in general, the active-backup configuration performs better than the active-active configuration. The thesis presents analytical and simulation methods to estimate signaling message overhead at the LTE EPC that arises due to the recovery process. It also analyzes the bandwidth requirements of the signaling traffic that is incurred by the other operational procedures of the self-healing scheme and their ramification to the LTE core network. / UOIT

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Approved for public release; distribution in unlimited. / As a consequence of the developments in information technology and the Internet, the world is getting increasingly dependent upon distributed systems and network services. Unfortunately, the security of these services has not kept pace with the advances in information technology itself. Security practitioners accept that, a system that is connected to an unbounded network, e.g., the Internet, will be vulnerable to attacks regardless of its security features. However, the emerging discipline of survivability can help ensure that such systems deliver essential services and maintain essential properties, such as integrity, confidentiality and performance, despite the presence of intrusions. Although survivability has been accepted as a means of sufficiently addressing the security problems of current network services, unfortunately, the studies that have been done on network survivability so far are not mature enough and they lack quantifiable metrics. To address this lack of network survivability measure, a global connectivity metric is developed in this thesis. Additionally, an election protocol based on this metric is designed for the SAAM prototype to enhance the survivability of the SAAM server. / Lieutenant Junior Grade, Turkish Navy

Power transmission grid infrastructures deliver electricity across large distance and are vital to the functioning of modern society. Increasingly these setups embody highly-coupled cyber-physical systems where advanced telecommunications networks are used to send status and control information to operate power transmission grid components, i.e., "smart grids". However, due to the high inter-dependency between the communication and power grid network layers, failure events can lead to further loss of control of key grid components, i.e., even if they are undamaged. In turn, such dependencies can exacerbate cascading failures and lead to larger electricity blackouts, particularly under disaster conditions. As a result, a range of studies have looked at modelling failures in interdependent smart grids. However most of these designs have not considered the use of proactive network-level survivability schemes. Indeed, these strategies can help maintain vital control connectivity during failures and potentially lead to reduced outages. Hence this thesis addresses this critical area and applies connection protection methodologies to reduce communication/control disruption in transmission grids. The performance of these schemes is then analyzed using detailed simulation for a sample IEEE transmission grid. Overall findings show a good reduction in the number of overloaded transmission lines when applying network-level recovery schemes.

In order to meet the availability requirements of modern communication networks, a number of survivability techniques were developed that adapt the demand-wise shared protection design model to incorporate strategies increasing network availability. The survivability methodologies developed took two approaches. The first incorporated availability directly into the network design model. The second ensured minimum dual failure restorability was set within the model. These methodologies were developed for predetermined topologies, as well as to have topology optimization incorporated into the model. All methodologies were implemented and analyzed on a set of samples. The analysis examined cost, topology and actual availability of the network designs. Availability design was effective but computationally intensive and difficult to design. Minimum dual failure restorability was also effective in increasing availability with a significant caveat, dual failure restorability increased exposure to possible failures, and without sufficient levels of dual failure restorability could have a negative impact on availability. / Engineering Management

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