[Truncated abstract] An ad-hoc network of wireless nodes is a temporarily formed network, created, operated and managed by the nodes themselves. Due to its peculiar establishment and operational properties it is also often termed an infrastructure-less, self-organised, or spontaneous network. In order to extend the communication range of the nodes, beyond a single hop, specially configured routing protocols are used. The unique feature of these protocols is their ability to form routes in spite of a dynamic topology. For effective functioning of the network it is essential that the network nodes execute the routing protocols in a truthful manner regardless of their contemporary commitments and workload. In real life, this is more than often extremely difficult to realise, and so we often find malicious nodes also present in the same network. These nodes can either join externally or may originate internally by compromis- ing an existing benevolent node in the network. These malicious nodes can carry out an array of attacks against the routing protocols leading to route severing, unavailability of service or deception. A number of secure routing protocols, which make use of cryptographic algorithms to secure the routes, have recently been proposed. ... In order to sustain the improvised nature of ad-hoc networks, in this thesis, we have moved from the common mechanism of achieving trust via security to enforcing dependability through collaboration. We desist from the customary strategy of employing cryptography and instead use a trust model that is influ- enced by the human behavioural model. All nodes in the network independently execute this trust model and maintain their own assessment concerning other nodes in the network. Each node, based upon its individual experiences, rewards collabo- rating nodes for their benevolent behaviour and penalises malicious nodes for their malevolent conduct. To highlight the efficacy of this unique approach, we apply the trust model to three contemporary reactive routing protocols in a pure ad-hoc network. These trust reinforced routing protocols locate dependable routes in the network by observing the sincerity in participation of other nodes using a set of trust categories. The routes worked out in this way are neither protected in terms of security nor minimal in terms of hops. However, these routes traverse nodes, which have been identified as more trustworthy than others and for this reason are more dependable in extemporised circumstances. Through the help of extensive simulations, we have demonstrated that the usage of these protocols significantly improves the overall performance of the network even in the presence of a high percentage of malicious nodes. These protocols, being independent of a trust infrastructure, also enable rapid deployment and improved operation with dynamic adaptation to the current scenario. The prime advantage being gained is the ability to seamlessly integrate ad-hoc wireless networks belonging to dissimilar organisations.

Thesis--Auburn University, 2009. / Abstract. Vita. Includes bibliographic resources (p.88-89).

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Includes bibliographical references (p. 164-173).

Vehicular Ad Hoc Network (VANET) supports wireless communication among vehicles using vehicle-to-vehicle (V2V) communication and between vehicles and infrastructure using vehicle-to-infrastructure (V2I) communication. This communication can be utilized to allow the distribution of safety and non-safety messages in the network. VANET supports a wide range of applications which rely on the messages exchanged within the network. Such applications will enhance the drivers' consciousness and improve their driving experience. However, the efficiency of these applications depends on the availability of vehicles real-time location information. A number of methods have been proposed to fulfill this requirement. However, designing a V2V-based localization method is challenged by the high mobility and dynamic topology of VANET and the interference noise due to objects and buildings. Currently, vehicle localization is based on GPS technology, which is not always reliable. Therefore, utilizing V2V communication in VANET can enhance the GPS positioning. With V2V-based localization, vehicles can determine their locations by exchanging mobility data among neighboring vehicles. In this research work, we address the above challenges and design a realistic V2V-based localization method that extends the centroid localization (CL) by assigning a weight value to each neighboring vehicle. This weight value is obtained using a weighting function that utilizes the following factors: 1) link quality distance between the neighboring vehicles 2) heading information and 3) map information. We also use fuzzy logic to model neighboring vehicles' weight values. Due to the sensitivity and importance of the exchanged information, it is very critical to ensure its integrity and reliability. Therefore, in this work, we present the design and the integration of a mobility data verification component into the proposed localization method, so that only verified data from trusted neighboring vehicles are considered. We also use subjective logic to design a trust management system to evaluate the trustworthiness of neighboring vehicles based on the formulated subjective opinions. Extensive experimental work is conducted using simulation programs to evaluate the performance of the proposed methods. The results show improvement on the location accuracy for varying vehicle densities and transmission ranges as well as in the presence of malicious/untrusted neighboring vehicles. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

This work presents the development of the Context-Aware Hybrid Data Dissemination protocol for vehicular networks. The importance of developing vehicular networking data dissemination protocols is exemplified by the recent announcement by the U.S. Department of Transportation (DOT) National Highway Traffic Safety Administration (NHTSA) to enable vehicle-to-vehicle (V2V) communication technology. With emphasis on safety, other useful applications of V2V communication include but are not limited to traffic and routing, weather, construction and road hazard alerts, as well as advertisement and entertainment. The core of V2V communication relies on the efficient dispersion of relevant data through wireless broadcast protocols for these varied applications. The challenges of vehicular networks demand an adaptive broadcast protocol capable of handling diverse applications. This research work illustrates the design of a wireless broadcast protocol that is context-aware and adaptive to vehicular environments taking into consideration vehicle density, road topology, and type of data to be disseminated. The context-aware hybrid data dissemination scheme combines store-and-forward and multi-hop broadcasts, capitalizing on the strengths of both these categories and mitigates the weaknesses to deliver data with maximum efficiency to a widest possible reach. This protocol is designed to work in both urban and highway mobility models. The behavior and performance of the hybrid data dissemination scheme is studied by varying the broadcast zone radius, aggregation ratio, data message size and frequency of the broadcast messages. Optimal parameters are determined and the protocol is then formulated to become adaptive to node density by keeping the field size constant and increasing the number of nodes. Adding message priority levels to propagate safety messages faster and farther than non-safety related messages is the next context we add to our adaptive protocol. We dynamically set the broadcast region to use multi-hop which has lower latency to propagate safety-related messages. Extensive simulation results have been obtained using realistic vehicular network scenarios. Results show that Context-Aware Hybrid Data Dissemination Protocol benefits from the low latency characteristics of multi-hop broadcast and low bandwidth consumption of store-and-forward. The protocol is adaptive to both urban and highway mobility models. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

Overlay networks have been the subject of significant research and practical interest recently in addressing the inefficiency and ossification of the current Internet. In this thesis, we cover various aspects of overlay network design, including overlay routing algorithms, overlay network assignment and multihomed overlay networks. We also examine the behavior of overlay networks under a wide range of network settings and identify several key factors that affect the performance of overlay networks. Based on these findings, practical design guidelines are also given. Specifically, this thesis addresses the following problems: 1) Dynamic overlay routing: We perform an extensive simulation study to investigate the performance of available bandwidth-based dynamic overlay routing from three important aspects: efficiency, stability, and safety margin. Based on the findings, we propose a hybrid routing scheme that achieves good performance in all three aspects. We also examine the effects of several factors on overlay routing performance, including network load, traffic variability, link-state staleness, number of overlay hops, measurement errors, and native sharing effects. 2) Virtual network assignment: We investigate the virtual network (VN) assignment problem in the scenario of network virtualization. Specifically, we develop a basic VN assignment scheme without reconfiguration and use it as the building block for all other advanced algorithms. Subdividing heuristics and adaptive optimization strategies are presented to further improve the performance. We also develop a selective VN reconfiguration scheme that prioritizes the reconfiguration for the most critical VNs. 3) Overlay network configuration tool for PlanetLab: We develop NetFinder, an automatic overlay network configuration tool to efficiently allocate PlanetLab resources to individual overlays. NetFinder continuously monitors the resource utilization of PlanetLab and accepts a user-defined overlay topology as input and selects the set of PlanetLab nodes and their interconnection for the user overlay. 4) Multihomed overlay network: We examine the effectiveness of combining multihoming and overlay routing from the perspective of an overlay service provider (OSP). We focus on the corresponding design problem and examine, with realistic network performance and pricing data, whether the OSP can provide a network service that is profitable, better (in terms of round-trip time), and less expensive than the competing native ISPs.

In recent years, mobile computing has become an integral part of society. As the cost of laptops and wireless networking hardware has declined, society has become increasingly connected. High speed wireless internet access is increasingly becoming part of our daily lives. As a result of this dependence on instant access to information, there is a growing need to create wireless networks without having access to a fixed networking infrastructure. Instead of relying in fixed infrastructure, these mobile nodes can be joined to create an ad hoc network to facilitate information sharing. The ad hoc nature of these networks requires different protocols than traditional networks. This research is motivated by the observation that radio communications are greatly affected by the physical environment. In hilly or urban environments, the performance of a wireless network is much lower than in large open areas. However, MANET protocols typically consider the physical environment only when it causes a change in connectivity. We examine whether the network can estimate the physical environment and predict its impact on the network, rather than waiting to react to the physical environment. This research demonstrates the feasibility of using terrain and location information to improve routing in mobile ad hoc networks through the development of a distributed routing algorithm that uses location and digital terrain information to efficiently deliver packets in a mobile ad hoc network. Through a comprehensive set of simulations, we show that the new algorithm performs better than current MANET protocols in terms of standard metrics: delay, throughput, packet loss, and efficiency.

In this dissertation research we study and address the unique challenges involved in information sharing and dissemination of large-scale group communication applications. We focus on system architectures and various techniques for efficient and scalable information dissemination in distributed P2P environments. Our solutions are developed by targeting at utilizing three representative P2P overlay networks: structured P2P network based on consistent hashing techniques, unstructured Gnutella-like P2P network, and P2P GeoGrid based on geographical location and proximity of end nodes. We have made three unique contributions to the general field of large-scale information sharing and dissemination. First, we propose a landmark-based peer clustering techniques to grouping end-system nodes by their network proximity, and a communication management technique addresses load balancing and reliability of group communication applications in structured P2P network. Second, we develop a utility-based P2P group communication service middleware, consisting of a utility-based topology management and a utility-aware P2P routing, for providing scalable and efficient group communication services in an unstructured P2P overlay network of heterogeneous peers. Third, we propose an overlay network management protocol that is aware of the geographical location of end-system nodes and a set of routing and adaptation techniques, aiming at building decentralized information dissemination service networks to support location-based applications and services. Although different overlay networks require different system designs for building scalable and efficient information dissemination services, we have employed two common design philosophies: (1) exploiting end-system heterogeneity and (2) utilizing proximity information of end-system nodes to localize most of the communication traffic, and (3) using randomized shortcuts to accelerate long-distant communications. We have demonstrated our design philosophies and the performance improvements in the above three types of P2P overlay networks. Concretely, by assigning more workloads to more powerful peers, we can greatly increase the system scalability and reduce the variation of workload distribution. By clustering end-system nodes based on their IP-network proximity or their geographical proximity, and utilizing randomized shortcuts, we can reduce the end-to-end communication latency, balance peer workloads against service request hotspots across the overlay network, and significantly enhance the scalability and efficiency of large-scale decentralized information dissemination and group communication.

With the emergence of computer networks as one of the primary platforms of communication, and with their adoption for an increasingly broad range of applications, there is a growing need for high-quality network traffic measurements to better understand, characterize and engineer the network behaviors. Due to the inherent lack of fine-grained measurement capabilities in the original design of the Internet, it does not have enough data or information to compute or even approximate some traffic statistics such as traffic matrices and per-link delay. While it is possible to infer these statistics from indirect aggregate measurements that are widely supported by network measurement devices (e.g., routers), how to obtain the best possible inferences is often a challenging research problem. We name this as "too little data" problem after its root cause. Interestingly, while "too little data" is clearly a problem, "too much data" is not a blessing either. With the rapid increase of network link speeds, even to keep sampled summarized network traffic (for inferring various network statistics) at low sample rates results in too much data to be stored, processed, and transmitted over measurement devices. In summary high-quality measurements in today's Internet is very challenging due to resource limitations and lack of built-in support, manifested as either "too little data" or "too much data". We present some new practices and proposals to alleviate these two problems.The contribution is four fold: i) designing universal methodologies towards ideal network traffic measurements; ii) providing accurate estimations for several critical traffic statistics guided by the proposed methodologies; iii) offering multiple useful and extensible building blocks which can be used to construct a universal network measurement system in the future; iv) leading to some notable mathematical results such as a new large deviation theorem that finds applications in various areas.

Traditional routing protocols select paths based on static link weights and converge to new paths only when there is an outright reachability failure (such as a link or router failure). This design allows routing scale to hundreds of thousands of nodes, but it comes at the cost of functionality: routing provides only simple, single path connectivity. Networked applications in the wide-area, enterprise, and data center can all benefit from network protocols that allow traffic to be sent over multiple routes en route to a destination. This ability, also called multipath routing, has other significant benefits over single-path routing, such as more efficiently using network resources and recovering more quickly from network disruptions. This dissertation explores the design of an architecture for path selection in the network and proposes a "narrow waist" interface for networks to expose choice in routing traffic to end systems. Because most networks are also business entities, and are sensitive to the cost of routing traffic in their network, this dissertation also develops a framework for exposing paths based on their cost. For this purpose, this dissertation develops a cost model for routing traffic in a network. In particular, this dissertation presents the following contributions: * Design of path bits, a "narrow waist" for multipath routing. Our work ties a large number of multipath routing proposals by creating an interface (path bits) for decoupling the multipath routing protocols implemented by the network and end systems (or other network elements) making a choice for path selection. Path bits permit simple, scalable, and efficient implementations of multipath routing protocols in the network that still provide enough expressiveness for end systems to select alternate paths. We demonstrate that our interface is flexible and leads to efficient network implementations by building prototype implementations on different hardware and software platforms. * Design of path splicing, a multipath routing scheme. We develop, path splicing, a multipath routing technique, which uses random perturbations from the shortest path to create exponentially large number of paths with only a linear increase in state in a network. We also develop a simple interface to enable end systems to make path selection decisions. We present various deployment paths for implementing path splicing in both intradomain and interdomain routing on the Internet. * Design of low cost path-selection framework for a network. Network operators and end systems can have conflicting goals, where the network operators are concerned with saving cost and reducing traffic uncertainty; and end systems favor better performing paths. Exposing choice of routing in the network can thus, create a tension between the network operators and the end systems. We propose a path-selection framework where end systems make path selection decisions based on path performance and networks expose paths to end systems based on their cost to the network. This thesis presents a cost model for routing traffic in a network to enable network operators to reason about "what-if " scenarios and routing traffic on their network.