Maximizing Reliability in WDM Networks Through Lightpath Routing

We study the reliability maximization problem in wavelength division multiplexing (WDM) networks with random link failures. Reliability in these networks is defined as the probability that the logical network is connected, and it is determined by the underlying lightpath routing, network topologies, and the link failure probability. By introducing the notion of lexicographical ordering for lightpath routings, we characterize precise optimization criteria for maximum reliability in the low failure probability regime. Based on the optimization criteria, we develop lightpath routing algorithms that maximize the reliability, and logical topology augmentation algorithms for further improving reliability. We also study the reliability maximization problem in the high failure probability regime.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-09-1-0050

Fairness in Communication and Computer Network Design

In communication networks, fair sharing of resources is an important issue for one main reason. The growth of network capacity is in general not matching the rapid growth of traffic. Consequently, the resources consumed by each user have to be limited. This implies that users cannot always be assigned the end-to-end bandwidth they ask for. Instead, the limited network resources should be distributed to users in a way that assures fair end-to-end bandwidth assignment among them. Obtaining fairness between network users and at the same time assuring efficient network utilization, is a source of non-trivial network optimization problems. Complicating factors are that each user has limited access to the (limited) network resources and that different users require and consume different amounts and types of resources. In this thesis different types of optimization problems associated with fair resource sharing in communication networks are studied. Initially, the notions of max-min fairness, proportional fairness, alpha-fairness etc., are put in a formal framework of fair rational preference relations. A clear, unified definition of fairness is presented. The theory is first applied to different types of allocation problems. Focus is put on convex and non-convex max-min fair traffic allocation problems, and a difference in difficulty between the two groups of problems is demonstrated. The studies are continued by an investigation of proportionally fair dimensioning. Two different cases are studied -- a simpler, when no resilience to failures is required, and a more complicated, assuming the possibility of link failures. In the context of fair sharing of the resources of a communication network, this thesis presents several original theoretical findings as well as solution algorithms for the studied problems. The results are accompanied by numerical results, illustrating algorithm efficiency for virtually all of the studied problems

Layered graph approaches for combinatorial optimization problems

Extending the concept of time-space networks, layered graphs associate information about one or multiple resource state values with nodes and arcs. While integer programming formulations based on them allow to model complex problems comparably easy, their large size makes them hard to solve for non-trivial instances. We detail and classify layered graph modeling techniques that have been used in the (recent) scientific literature and review methods to successfully solve the resulting large-scale, extended formulations. Modeling guidelines and important observations concerning the solution of layered graph formulations by decomposition methods are given together with several future research directions

Efficient network camouflaging in wireless networks

Camouflaging is about making something invisible or less visible. Network camouflaging is about hiding certain traffic information (e.g. traffic pattern, traffic flow identity, etc.) from internal and external eavesdroppers such that important information cannot be deduced from it for malicious use. It is one of the most challenging security requirements to meet in computer networks. Existing camouflaging techniques such as traffic padding, MIX-net, etc., incur significant performance degradation when protected networks are wireless networks, such as sensor networks and mobile ad hoc networks. The reason is that wireless networks are typically subject to resource constraints (e.g. bandwidth, power supply) and possess some unique characteristics (e.g. broadcast, node mobility) that traditional wired networks do not possess. This necessitates developing new techniques that take account of properties of wireless networks and are able to achieve a good balance between performance and security. In this three-part dissertation we investigate techniques for providing network camouflaging services in wireless networks. In the first part, we address a specific problem in a hierarchical multi-task sensor network, i.e. hiding the links between observable traffic patterns and user interests. To solve the problem, a temporally constant traffic pattern, called cover traffic pattern, is needed. We describe two traf- fic padding schemes that implement the cover traffic pattern and provide algorithms for achieving the optimal energy efficiencies with each scheme. In the second part, we explore the design of a MIX-net based anonymity system in mobile ad hoc networks. The objective is to hide the source-destination relationship with respect to each connection. We survey existing MIX route determination algorithms that do not account for dynamic network topology changes, which may result in high packet loss rate and large packet latency. We then introduce adaptive algorithms to overcome this problem. In the third part, we explore the notion of providing anonymity support at MAC layer in wireless networks, which employs the broadcast property of wireless transmission. We design an IEEE 802.11-compliant MAC protocol that provides receiver anonymity for unicast frames and offers better reliability than pure broadcast protocol

visone - Software for the Analysis and Visualization of Social Networks

We present the software tool visone which combines graph-theoretic methods for the analysis of social networks with tailored means of visualization. Our main contribution is the design of novel graph-layout algorithms which accurately reflect computed analyses results in well-arranged drawings of the networks under consideration. Besides this, we give a detailed description of the design of the software tool and the provided analysis methods

Crosslayer Survivability in Overlay-IP-WDM Networks

As the Internet moves towards a three-layer architecture consisting of overlay networks on top of the IP network layer on top of WDM-based physical networks, incorporating the interaction between and among network layers is crucial for efficient and effective implementation of survivability.This dissertation has four major foci as follows: First, a first-of-its-kind analysis of the impact of overlay network dependency on the lower layer network unveils that backhaul, a link loop that occurs at any two or more lower layers below the layer where traffic is present, could happen. This prompts our proposal of a crosslayer survivable mapping to highlight such challenges and to offer survivability in an efficient backhaul-free way. The results demonstrate that the impact of layer dependency is more severe than initially anticipated making it clear that independent single layer network design is inadequate to assure service guarantees and efficient capacity allocation. Second, a forbidden link matrix is proposed masking part of the network for use in situations where some physical links are reserved exclusively for a designated service, mainly for the context of providing multiple levels of differentiation on the network use and service guarantee. The masking effect is evaluated on metrics using practical approaches in a sample real-world network, showing that both efficiency and practicality can be achieved. Third, matrix-based optimization problem formulations of several crosslayer survivable mappings are presented; examples on the link availability mapping are particularly illustrated. Fourth, survivability strategies for two-layer backbone networks where traffic originates at each layer are investigated. Optimization-based formulations of performing recovery mechanisms at each layer for both layers of traffic are also presented. Numerical results indicate that, in such a wavelength-based optical network, implementing survivability of all traffic at the bottom layer can be a viable solution with significant advantages.This dissertation concludes by identifying a roadmap of potential future work for crosslayer survivability in layered network settings

Journal of Telecommunications and Information Technology, 2017, nr 1

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