Alibi framework for identifying reactive jamming nodes in wireless LAN

Reactive jamming nodes are the nodes of the network that get compromised and become the source of jamming attacks. They assume to know any shared secrets and protocols used in the networks. Thus, they can jam very effectively and are very stealthy. We propose a novel approach to identifying the reactive jamming nodes in wireless LAN (WLAN). We rely on the half-duplex nature of nodes: they cannot transmit and receive at the same time. Thus, if a compromised node jams a packet, it cannot guess the content of the jammed packet. More importantly, if an honest node receives a jammed packet, it can prove that it cannot be the one jamming the packet by showing the content of the packet. Such proofs of jammed packets are called "alibis" - the key concept of our approach. In this paper, we present an alibi framework to deal with reactive jamming nodes in WLAN. We propose a concept of alibi-safe topologies on which our proposed identification algorithms are proved to correctly identify the attackers. We further propose a realistic protocol to implement the identification algorithm. The protocol includes a BBC-based timing channel for information exchange under the jamming situation and a similarity hashing technique to reduce the storage and network overhead. The framework is evaluated in a realistic TOSSIM simulation where the simulation characteristics and parameters are based on real traces on our small-scale MICAz test-bed. The results show that in reasonable dense networks, the alibi framework can accurately identify both non-colluding and colluding reactive jamming nodes. Therefore, the alibi approach is a very promising approach to deal with reactive jamming nodes.published or submitted for publicationnot peer reviewe

Towards Timeliness and Reliability Analysis of Distributed Content-based Publish/Subscribe Systems over Best-effort Networks

Content-based publish/subscribe is a powerful data dissemination paradigm that offers both scalability and flexibility. However, its nature of high expressiveness makes it difficult to analyze or predict the behavior of the system such as event delivery probability and end-to-end delivery delay, especially when deployed over unreliable, best-effort public networks. This paper proposes the analytical model that abstracts expressiveness nature of content-based publish/subscribe, along with uncertainty of underlying networks, in order to predict quality of service in terms of delivery probability and timeliness based on partial, imprecise statistical attributes of each component in the system. Furthermore, the paper leverages the proposed prediction algorithm to implements heuristic-based subscriber admission control algorithms to maximize system utility when the system cannot support all subscribers. The evaluation results yields good prediction accuracy and admission rates.published or submitted for publicationis peer reviewe

The Analysis of Publish/Subscribe Systems over Mobile Wireless Ad Hoc Networks\

In this work, we analyze the publish/subscribe distributed system paradigm over mobile ad hoc networks with respect to the performance and the impact of different mobility speeds and patterns of all participants in urban and high-way scenarios. In order to handle mobility, our publish/subscribe framework relies on light-weight publish/subscribe brokers, which are chosen in a topic-driven fashion. With the option of geographic location and waypoint information, we discuss several publish/subscribe variants and analyze their advantages/disadvantages when applied in different mobility environment. Via simulations, we measure quality of service in terms of delivery ratio and message delay achieved by such different publish/subscribe schemes over different scenarios and mobility models.published or submitted for publicationis peer reviewe

Reliability and timeliness analysis of content-based publish/subscribe systems

Content-based Publish/subscribe systems (CBPS) is a simple yet powerful communication paradigm. Its content-centric nature is suitable for a wide spectrum of today's content-centric applications such as stock market quote exchange, remote monitoring and surveillance, RSS news feed, and online gaming. As the trend shows that the amount of information along with its producers become astonishingly increasing everyday, a publish/subscribe system seems to be one of only a few viable choices that could govern the next-generation world of communication. However, the content-centric nature of a publish/subscribe system also poses difficulty in analyzing or assessing its performance. Moreover, the complexity increases when deploying a publish/subscribe system on top of best-effort, unreliable wide-area networks. Such uncertainty and complexity become a hindrance to apply content-based publish/subscribe systems to delay-sensitive applications that require reliable/timely event delivery and tight resource control such as soft real-time systems or cyber-physical systems. The need to solve such problem calls for a good analytical model that could capture both expressiveness and uncertainty nature of distributed CBPS systems yet predict the system behavior accurately. This dissertation is, to the best our knowledge, the first attempt to analyze the reliability/timeliness performance of distributed content-based publish/subscribe systems under best-effort networks. It proposes a probabilistic, analytical framework of content-based publish/subscribe systems under different dynamism for the purpose of performance analysis. Specifically, given a publish/subscribe system configuration and dynamism parameters, it estimates event delivery probability and timeliness received by each subscriber in the publish/subscribe system. The dissertation also presents evaluation results of the proposed predictive model via simulations with both synthetic traces and real-world traces. The results yield prediction accuracy and effectiveness of the proposed framework. The proposed analytical framework can be used as a tool for performance assessment or as a building block for publish/subscribe system optimizations such as subscriber admission control, subscriber allocation, broker capacity planning, and broker network planning. There are several factors, which are termed dynamism in this dissertation, that affect the performance of distributed content-based publish/subscribe systems. The proposed analytical framework first addresses each type of dynamism separately in order to avoid the modeling complexity and to study the effect of each type of dynamism individually. The proposed analytical model then relaxes each assumption and combine several types of dynamism altogether under one integrated framework. There are three major types of dynamism considered in the analytical framework : content dynamism, overlay dynamism, and mobility dynamism. Content dynamism means the uncertainty in determining the amount of data from an arbitrary publisher to an arbitrary subscriber due to the publisher-subscriber decoupling nature of the content-based publish/subscribe systems. Overlay dynamism means the uncertainty from publish/subscribe internal broker network, including broker failures and link failures. Finally, mobility dynamism refers to the uncertainty from users' changes of location and content interest. We first propose a probabilistic analytical model for each type of dynamism separately before discussing the framework that integrates all separate analytical models together. We also present validation results for each dynamism-specific analytical model, which prove the accuracy and effectiveness of its corresponding analytical model. This thesis makes contributions in the following areas. First, it proposes a detailed analytical model of content-based publish/subscribe systems from all possible aspects, providing a complete analysis in systematic manner. Second, it incorporates delay and reliability into one single analytical framework, which makes it suitable for delay-sensitive publish/subscribe applications. Third, it discusses and proposes some examples of possible publish/subscribe optimizations on top of such analytical model. Finally, it proves the applicability of the proposed analytical model via simulations with both synthetic and real-world traces

AVCast: New Approaches For Implementing Availability-Dependent Reliability for Multicast Receivers

Today's large-scale distributed systems consist of a collection of nodes that have highly variable availability . a phenomenon sometimes called churn. This availability variation is often a hindrance to achieving reliability and performance for distributed applications such as multicast. This paper looks into utilizing and leveraging availability information in order to provide availability-dependent message reliability for multicast receivers. An application (e.g., a publish-subscribe system) may want to scale the multicast message reliability on each receiver according to its availability .different options are that the reliability is independent of the availability, or proportional to it, or is some other arbitrary function of it. We propose several gossip-based algorithms to support several such predicates. These techniques rely on each node.s availability being monitored in a distributed manner by a small group of other nodes in such a way that the monitoring load is evenly distributed in the system. Our techniques are light-weight, scalable, and are space- and time- efficient. We analyze our algorithms and evaluate them experimentally by using availability traces collected from real peer-to-peer systems

Alibi: A novel approach for detecting insider-based jamming attacks in wireless networks

We consider the problem of detecting the insiderbased attacks in the form of jammers in a single-hop wireless LAN environment, where jammers have the inside knowledge of frequency hopping patterns and any protocols used in the wireless network. We propose a novel jammer model in which the jammers are modeled by the number of channels that they can jam simultaneously. We further propose the novel concept of an atomic jammer which is the basic component necessary to deal with stronger jammers. To deal with atomic jammers, we propose a class of novel protocols called alibi protocols. The basic idea of the alibi protocols is to exploit one major limitation of the atomic jammers: they cannot jam two channels at the same time. Therefore, honest nodes in the network can occasionally switch to another channel, called the alibi channel, to transmit proofs for their honesty witnessed by some other honest nodes. We specify a necessary condition and desired properties such as detection time, false alarms and miss detections of this class of protocols. We prove that with high probability the detection time of these protocols is O(n ln(n)). We also propose some more practical alibi-based protocols such as 1-propagation and 1-gossiping and prove their desired properties. We further extend our work to the lossy channel model. The simulation results in ns2 confirm our analysis. The overall results of these protocols show a promising research direction to deal with insider-based jamming attacks

HybridCast: A Hybrid Probabilistic/Deterministic Approach for Adjustable Broadcast Reliability in Mobile Wireless Ad Hoc Networks

Broadcast is a crucial yet expensive building block for many applications in bandwidth-scarce mobile wireless ad hoc networks. We propose a hybrid deterministic/probabilistic, decentralized broadcast protocol with adjustable broadcast reliability and overhead. The paper ???rst proposes a purely probabilistic, topology-aware broadcast algorithm. The probabilistic broadcast adjusts each node???s broadcast forwarding probability locally such that the average broadcast reliability requirement is met. An extension of the probabilistic broadcast to tolerate node mobility and packet loss is then presented. Furthermore, the paper augments the proposed probabilistic broadcast scheme with an existing deterministic broadcast protocol in order to reduce excessive broadcast overhead. The proposed hybrid protocol, called HybridCast, combines good characteristics of probabilistic broadcasts, such as adjustable reliability and resilience to mobility, with good characteristics of deterministic broadcasts, such as few retransmissions and low packet collisions. The simulation results show that the proposed protocol can achieve the system???s reliability requirement with good tolerance to mobility and packet losses while incurring low broadcast overhead.published or submitted for publicationis peer reviewe

Reliability Trade-off Analysis of Deadline-Sensitive Wireless Messaging Systems

The need for deadline-sensitive messaging systems is growing fast with the growth in the number of mobile and static devices communicating with each other. With many such devices from different locations exchanging messages over a network, understanding the reliability of message delivery so as to cost-effectively improve it becomes challenging. The analysis is even more challenging and complex when some or most of the nodes are moving at different speeds following different mobility patterns and when the network is wireless. In this paper we present a reliability trade-off analysis for the exchange of messages between nodes under different mobility scenarios and various parameters using simulation. Some of the nodes in our study are message servers which are responsible for the control and delivery (relay) of messages from one client node to another client node. Among other things, our simulation results show that a message reliability of greater than 75% can be obtained using a method of smart server selection and more servers or a higher transmission range if the servers are not moving. However with a method of random server selection or if servers are moving a 75% message reliability cannot be achieved even using more servers and a higher range. The higher the packet sending rate by the clients, the higher the file reliability ( specially for bigger files and smaller transmission ranges). For chat messaging, the reliability usually increases as the speed of the nodes (clients) increases.published or submitted for publicationnot peer reviewe