Airborne Network Data Availability Using Peer to Peer Database Replication on a Distributed Hash Table

The concept of distributing one complex task to several smaller, simpler Unmanned Aerial Vehicles (UAVs) as opposed to one complex UAV is the way of the future for a vast number of surveillance and data collection tasks. One objective for this type of application is to be able to maintain an operational picture of the overall environment. Due to high bandwidth costs, centralizing all data may not be possible, necessitating a distributed storage system such as mobile Distributed Hash Table (DHT). A difficulty with this maintenance is that for an Airborne Network (AN), nodes are vehicles and travel at high rates of speed. Since the nodes travel at high speeds they may be out of contact with other nodes and their data becomes unavailable. To address this the DHT must include a data replication strategy to ensure data availability. This research investigates the percentage of data available throughout the network by balancing data replication and network bandwidth. The DHT used is Pastry with data replication using Beehive, running over an 802.11 wireless environment, simulated in Network Simulator 3. Results show that high levels of replication perform well until nodes are too tightly packed inside a given area which results in too much contention for limited bandwidth

Self-organizing peer-to-peer social networks

This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2008 The Authors.Peer-to-peer (P2P) systems provide a new solution to distributed information and resource sharing because of its outstanding properties in decentralization, dynamics, flexibility, autonomy, and cooperation, summarized as DDFAC in this paper. After a detailed analysis of the current P2P literature, this paper suggests to better exploit peer social relationships and peer autonomy to achieve efficient P2P structure design. Accordingly, this paper proposes Self-organizing peer-to-peer social networks (SoPPSoNs) to self-organize distributed peers in a decentralized way, in which neuron-like agents following extended Hebbian rules found in the brain activity represent peers to discover useful peer connections. The self-organized networks capture social associations of peers in resource sharing, and hence are called P2P social networks. SoPPSoNs have improved search speed and success rate as peer social networks are correctly formed. This has been verified through tests on real data collected from the Gnutella system. Analysis on the Gnutella data has verified that social associations of peers in reality are directed, asymmetric and weighted, validating the design of SoPPSoN. The tests presented in this paper have also evaluated the scalability of SoPPSoN, its performance under varied initial network connectivity and the effects of different learning rules.National Natural Science of Foundation of Chin

Ad-hoc Stream Adaptive Protocol

With the growing market of smart-phones, sophisticated applications that do extensive computation are common on mobile platform; and with consumers’ high expectation of technologies to stay connected on the go, academic researchers and industries have been making efforts to find ways to stream multimedia contents to mobile devices. However, the restricted wireless channel bandwidth, unstable nature of wireless channels, and unpredictable nature of mobility, has been the major road block for wireless streaming advance forward. In this paper, various recent studies on mobility and P2P system proposal are explained and analyzed, and propose a new design based on existing P2P systems, aimed to solve the wireless and mobility issues

Secure identity management in structured peer-to-peer (P2P) networks

Structured Peer-to-Peer (P2P) networks were proposed to solve routing problems of big distributed infrastructures. But the research community has been questioning their security for years. Most prior work in security services was focused on secure routing, reputation systems, anonymity, etc. However, the proper management of identities is an important prerequisite to provide most of these security services. The existence of anonymous nodes and the lack of a centralized authority capable of monitoring (and/or punishing) nodes make these systems more vulnerable against selfish or malicious behaviors. Moreover, these improper usages cannot be faced only with data confidentiality, nodes authentication, non-repudiation, etc. In particular, structured P2P networks should follow the following secure routing primitives: (1) secure maintenance of routing tables, (2) secure routing of messages, and (3) secure identity assignment to nodes. But the first two problems depend in some way on the third one. If nodes’ identifiers can be chosen by users without any control, these networks can have security and operational problems. Therefore, like any other network or service, structured P2P networks require a robust access control to prevent potential attackers joining the network and a robust identity assignment system to guarantee their proper operation. In this thesis, firstly, we analyze the operation of the current structured P2P networks when managing identities in order to identify what security problems are related to the nodes’ identifiers within the overlay, and propose a series of requirements to be accomplished by any generated node ID to provide more security to a DHT-based structured P2P network. Secondly, we propose the use of implicit certificates to provide more security and to exploit the improvement in bandwidth, storage and performance that these certificates present compared to explicit certificates, design three protocols to assign nodes’ identifiers avoiding the identified problems, while maintaining user anonymity and allowing users’ traceability. Finally, we analyze the operation of the most used mechanisms to distribute revocation data in the Internet, with special focus on the proposed systems to work in P2P networks, and design a new mechanism to distribute revocation data more efficiently in a structured P2P network.Las redes P2P estructuradas fueron propuestas para solventar problemas de enrutamiento en infraestructuras de grandes dimensiones pero su nivel de seguridad lleva años siendo cuestionado por la comunidad investigadora. La mayor parte de los trabajos que intentan mejorar la seguridad de estas redes se han centrado en proporcionar encaminamiento seguro, sistemas de reputación, anonimato de los usuarios, etc. Sin embargo, la adecuada gestión de las identidades es un requisito sumamente importante para proporcionar los servicios mencionados anteriormente. La existencia de nodos anónimos y la falta de una autoridad centralizada capaz de monitorizar (y/o penalizar) a los nodos hace que estos sistemas sean más vulnerables que otros a comportamientos maliciosos por parte de los usuarios. Además, esos comportamientos inadecuados no pueden ser detectados proporcionando únicamente confidencialidad de los datos, autenticación de los nodos, no repudio, etc. Las redes P2P estructuradas deberían seguir las siguientes primitivas de enrutamiento seguro: (1) mantenimiento seguro de las tablas de enrutamiento, (2) enrutamiento seguro de los mensajes, and (3) asignación segura de las identidades. Pero la primera de los dos primitivas depende de alguna forma de la tercera. Si las identidades de los nodos pueden ser elegidas por sus usuarios sin ningún tipo de control, muy probablemente aparecerán muchos problemas de funcionamiento y seguridad. Por lo tanto, de la misma forma que otras redes y servicios, las redes P2P estructuradas requieren de un control de acceso robusto para prevenir la presencia de atacantes potenciales, y un sistema robusto de asignación de identidades para garantizar su adecuado funcionamiento. En esta tesis, primero de todo analizamos el funcionamiento de las redes P2P estructuradas basadas en el uso de DHTs (Tablas de Hash Distribuidas), cómo gestionan las identidades de sus nodos, identificamos qué problemas de seguridad están relacionados con la identificación de los nodos y proponemos una serie de requisitos para generar identificadores de forma segura. Más adelante proponemos el uso de certificados implícitos para proporcionar más seguridad y explotar las mejoras en consumo de ancho de banda, almacenamiento y rendimiento que proporcionan estos certificados en comparación con los certificados explícitos. También hemos diseñado tres protocolos de asignación segura de identidades, los cuales evitan la mayor parte de los problemas identificados mientras mantienen el anonimato de los usuarios y la trazabilidad. Finalmente hemos analizado el funcionamiento de la mayoría de los mecanismos utilizados para distribuir datos de revocación en Internet, con especial interés en los sistemas propuestos para operar en redes P2P, y hemos diseñado un nuevo mecanismo para distribuir datos de revocación de forma más eficiente en redes P2P estructuradas.Postprint (published version

Location-aware mechanism for efficient video delivery over wireless mesh networks

Due to their flexibility, ease of use, low-cost and fast deployment, wireless Mesh Networks have been widely accepted as an alternative to wired network for last-mile connectivity. When used in conjunction with Peer-to-Peer data transfer solutions, many innovative applications and services such as distributed storage, resource sharing, live TV broadcasting or Video on Demand can be supported without any centralized administration. However, in order to achieve a good quality of service in such variable, error-prone and resource-constrained wireless multi-hop environments, it is important that the associated Peer-to-Peer overlay is not only aware of the availability, but also of the location and available path link quality of its peers and services. This thesis proposes a wireless location-aware Chord-based overlay mechanism for Wireless Mesh Networks (WILCO) based on a novel geographical multi-level ID mapping and an improved finger table. The proposed scheme exploits the location information of mesh routers to decrease the number of hops the overlay messages traverse in the physical topology. Analytical and simulation results demonstrate that in comparison to the original Chord, WILCO has significant benefits: it reduces the number of lookup messages, has symmetric lookup on keys in both the forward and backward direction of the Chord ring and achieves a stretch factor of O(1). On top of this location-aware overlay, a WILCO-based novel video segment seeking algorithm is proposed to make use of the multi-level WILCO ID location-awareness to locate and retrieve requested video segments from the nearest peer in order to improve video quality. An enhanced version of WILCO segment seeking algorithm (WILCO+) is proposed to mitigate the sometimes suboptimal selection of the WILCO video segment seeking algorithm by extracting coordinates from WILCO ID to enable location-awareness. Analytical and simulation results illustrate that the proposed scheme outperforms the existing state-of-the-art solutions in terms of PSNR and packet loss with different background traffic loads. While hop count is frequently strongly correlated to Quality of Service, the link quality of the underlying network will also have a strong influence on content retrieval quality. As a result, a Cross-layer Wireless Link Quality-aware Overlay peer selection mechanism (WLO) is proposed. The proposed cross-layer mechanism uses a Multiplication Selector Metric (MSM) to select the best overlay peer. The proposed MSM overcomes the two issues facing the traditional summation-based metric, namely, the difficulty of bottleneck link identification and the influence of hop count on behavior. Simulation results show that WLO outperforms the existing state-of-the-art solutions in terms of video quality at different background loads and levels of topology incompleteness. Real life emulation-based tests and subjective video quality assessments are also performed to show that the simulation results are closely matched by the real-life emulation-based results and to illustrate the significant impact of overlay peer selection on the user perceived video quality

TDMA Slot Reservation in Cluster-Based VANETs

Vehicular Ad Hoc Networks (VANETs) are a form of Mobile Ad Hoc Networks (MANETs) in which vehicles on the road form the nodes of the network. VANETs provide several services to enhance the safety and comfort of drivers and passengers. These services can be obtained by the wireless exchange of information among the vehicles driving on the road. In particular, the transmission of two different types of messages, safety/update and non-safety messages. The transmission of safety/update message aims to inform the nearby vehicles about the sender\u27s current status and/or a detected dangerous situation. This type of transmission is designed to help in accident and danger avoidance. Moreover, it requires high message generated rate and high reliability. On the other hand, the transmission of non-safety message aims to increase the comfort on vehicles by supporting several non-safety services, from notifications of traffic conditions to file sharing. Unfortunately, the transmission of non-safety message has less priority than safety messages, which may cause shutting down the comfort services. The goal of this dissertation is to design a MAC protocol in order to provide the ability of the transmission of non-safety message with little impact on the reliability of transmitting safety message even if the traffic and communication densities are high. VANET is a highly dynamic network. With lack of specialized hardware for infrastructure and the mobility to support network stability and channel utilization, acluster-based MAC protocol is needed to solve these overcomes. This dissertation makes the following contributions: 1. A multi-channel cluster-based TDMA MAC protocol to coordinate intracluster communications (TC-MAC) 2. A CH election and cluster formation algorithm based on the traffic flow and a cluster maintenance algorithm that benefits from our cluster formation algorithm 3. A multi-channel cluster-based CDNIA/TDMA hybrid MAC protocol to coordinate inter-cluster communications I will show that TC-MAC provides better performance than the current WAVE standard in terms of safety/update message reliability and non-safety message delivery. Additionally, I will show that my clustering and cluster maintenance protocol provides more stable clusters, which will reduce the overhead of clusterhead election and re-clustering and leads to an efficient hierarchical network topology

Opportunistic P2P Communications in Delay-Tolerant Rural Scenarios

Opportunistic networking represents a promising paradigm for support of communications, specifically in infrastructureless scenarios such as remote areas communications. In principle in opportunistic environments, we would like to make available all the applications thought for traditional wired and wireless networks like file-sharing and content distribution. In this paper, we present a delay-tolerant scenario for file sharing applications in rural areas, where an opportunistic approach is exploited. In order to support communications, we compare two peer-to-peer (P2P) schemes initially conceived for wireless networks and prove their applicability and usefulness to a DTN scenario, where replication of resources can be used to improve the lookup performance and the network can be occasionally connected by means of a data mule. Simulation results show the suitability of the schemes and allow to derive interesting design guidelines on the convenience and applicability of such approaches