Moonjeong Chang

Dynamic Trust Management for Delay Tolerant Networks and Its Application to Secure Routing

Delay tolerant networks (DTNs) are characterized by high end-to-end latency, frequent disconnection, and opportunistic communication over unreliable wireless links. In this paper, we design and validate a dynamic trust management protocol for secure routing optimization in DTN environments in the presence of well-behaved, selfish and malicious nodes. We develop a novel model-based methodology for the analysis of our trust protocol and validate it via extensive simulation. Moreover, we address dynamic trust management, i.e., determining and applying the best operational settings at runtime in response to dynamically changing network conditions to minimize trust bias and to maximize the routing application performance. We perform a comparative analysis of our proposed routing protocol against Bayesian trust-based and non-trust based (PROPHET and epidemic) routing protocols. The results demonstrate that our protocol is able to deal with selfish behaviors and is resilient against trust-related attacks. Furthermore, our trust-based routing protocol can effectively trade off message overhead and message delay for a significant gain in delivery ratio. Our trust-based routing protocol operating under identified best settings outperforms Bayesian trust-based routing and PROPHET, and approaches the ideal performance of epidemic routing in delivery ratio and message delay without incurring high message or protocol maintenance overhead.

Trust Management for Encounter-Based Routing in Delay Tolerant Networks

We propose and analyze a class of trust management protocols for encounter-based routing in delay tolerant networks (DTNs). The underlying idea is to incorporate trust evaluation in the routing protocol, considering not only quality-of-service (QoS) trust properties (connectivity) but also social trust properties (honesty and unselfishness) to evaluate other nodes encountered. Two versions of trust management protocols are considered: an equal-weight QoS and social trust management protocol (called trust-based routing) and a QoS only trust management protocol (called connectivity-based routing). By utilizing a stochastic Petri net model describing a DTN behavior, we analyze the performance characteristics of these two routing protocols in terms of message delivery ratio, latency, and message overhead. We also perform a comparative performance analysis with epidemic routing for a DTN consisting of heterogeneous mobile nodes with vastly different social and networking behaviors. The results indicate that trust-based routing approaches the ideal performance of epidemic routing in delivery ratio, while connectivity-based routing approaches the ideal performance in message delay of epidemic routing, especially as the percentage of selfish and malicious nodes present in the DTN system increases. By properly selecting weights associated with QoS and social trust metrics for trust evaluation, our trust management protocols can approximate the ideal performance obtainable by epidemic routing in delivery ratio and message delay without incurring high message overhead.

A Transport Layer Mobility Support Mechanism

Recently, mobile SCTP (mSCTP) has been proposed as a transport layer approach for supporting mobility. mSCTP is based on the ’multi-homing’ feature of Stream Control Transmission Protocol (SCTP), and utilize the functions to dynamically add or delete IP addresses of end points to or from the existing connection in order to support mobility. In this paper, we propose a mechanism to determine when to add or delete an IP address, utilizing the link layer radio signal strength information in order to enhance the performance of mSCTP. We also propose a mechanism for a mobile node to initiate the change of data delivery path based on link layer radio signal strength information. The simulation results show that the performance of proposed transport layer mobility support mechanism is competitive compared to the traditional network layer mobility supporting approach. Especially, when the moving speed of mobile node is fast, it shows better performance than the traditional network layer approach.

Integrated Social and QoS Trust-Based Routing in Delay Tolerant Networks

We propose and analyze a class of integrated social and quality of service (QoS) trust-based routing protocols in mobile ad-hoc delay tolerant networks. The underlying idea is to incorporate trust evaluation in the routing protocol, considering not only QoS trust properties but also social trust properties to evaluate other nodes encountered. We prove that our protocol is resilient against bad-mouthing, good-mouthing and whitewashing attacks performed by malicious nodes. By utilizing a stochastic Petri net model describing a delay tolerant network consisting of heterogeneous mobile nodes with vastly different social and networking behaviors, we analyze the performance characteristics of trust-based routing protocols in terms of message delivery ratio, message delay, and message overhead against connectivity-based, epidemic and PROPHET routing protocols. The results indicate that our trust-based routing protocols outperform PROPHET and can approach the ideal performance obtainable by epidemic routing in delivery ratio and message delay, without incurring high message overhead. Further, integrated social and QoS trust-based protocols can effectively trade off message delay for a significant gain in message delivery ratio and message overhead over traditional connectivity-based routing protocols.

Hierarchical trust management for wireless sensor networks and its application to trust-based routing

In this work, we propose a highly scalable cluster-based hierarchical trust management protocol for wireless sensor networks to effectively deal with selfish or malicious nodes. Unlike prior work, we consider multidimensional trust attributes derived from communication and social networks to evaluate the overall trust of a sensor node. Our peer-to-peer trust evaluation method leverages the cluster-based hierarchical structure for efficient communications. We develop a probability model using stochastic Petri net techniques to analyze the performance of the proposed trust management protocol. We validate the protocol design by comparing subjective trust generated as a result of protocol execution against objective trust obtained from actual node status. We apply our hierarchical trust management protocol to trust-based geographical routing as an application. Our results demonstrate that trust-based geographic routing under identified design settings can approach the ideal performance level achievable by flooding-based routing in message delivery ratio and message delay without incurring substantial message overhead. Furthermore, it can significantly outperform traditional geographic routing protocols that do not use trust concept in selecting forwarding nodes in message delivery ratio over a wide range of design parameter settings.

A per-application mobility management platform for application-specific handover decision in overlay networks

With the advance of various wireless access technologies, the demand for a mobile user equipped with multiple air interfaces simultaneously executing diverse applications emerged. In such network environments, per-application mobility management is a key to allow each application of an end user device to dynamically and fully take advantage of the most suitable access technology. In this paper, we devised a comprehensive architectural platform with cross-layer techniques to realize this disruptive technology, i.e., per-application mobility management. The proposed platform enables the triggering of vertical handover decisions based on the dynamic measurements from the entire protocol stack. For per-application, the handover decision as well as the mobility management and the transport/application protocol control adaptation for handover performance optimization are made with cross-layer techniques. Through the simulation results, it is shown that multi-layer handover triggering of the proposed platform enhances the QoS of the application services by making handover decisions when the QoS requirements of an application is not satisfied as well as when a mobile user moves out of the current access network in overlay network environments. It is also presented that per-application handover based on the proposed platform enhances the QoS of the application services compared to the handover approaches which make every on-going service flows handover together to the same access network.

An enhancement of transport layer approach to mobility support

In this paper, we propose an approach to transport layer mobility support leveraging the SCTP extension dubbed dynamic address reconfiguration. Timing issues related to the end-to-end address management, and a novel error recovery mechanism associated with a handover are discussed. The error recovery time of proposed mechanism is analyzed and compared to that of the plain SCTP for handover cases. Finally, through a series of simulations, the performance of the proposed SCTP enhancements over plain IPv6 is compared with the MIPv6 and its variants (i.e., HMIPv6 and FMIPv6) with TCP Reno on top of them. The simulation results present the performance gains of the pro-posed error recovery mechanism, which is possible within the context of transport layer mobility management.

Per-Application Mobility Management with Cross-Layer Based Performance Enhancement

With the advance of various wireless access technologies, the demand for a mobile user equipped with multiple air interfaces simultaneously executing diverse applications emerged. In such network environment, per- application mobility management is a key to allow each application of an end user device to dynamically and fully take advantage of the most suitable access technology. In this paper, we devised a comprehensive architectural platform with cross- layer techniques to realize this disruptive technology, i.e., per- application mobility management. Four core functional modules composing the proposed platform for end user devices are defined: Monitoring Agents, Profile Database, Decision Engine, and IP Agent. We show through simulations that the presented platform provides an improved QoS as it selectively utilizes the best available networks depending on different QoS constraints of different applications.

Trust and independence aware decision fusion in distributed networks

In distributed network environments, decisions must often be made based on incomplete or uncertain evidence whose sources may be dependent. Properly fusing potentially unreliable and dependent information from multiple sources is critical to effective decision making. The Transferable Belief Model (TBM), an extension of Dempster-Shafer Theory (DST), is a well known information fusion framework that can cope with conflicting evidences. However, neither DST nor TBM deals with misbehaving data sources and dependence of fusion data, which are often observed in dynamic multi-hop network environments. In this work, we propose a decision fusion framework that considers multi-dimensional trust and independence of information using a provenance technique, to enhance fusion reliability. We consider three information trust dimensions: correctness, completeness, and timeliness. Our simulation results show that the proposed framework yields a higher correct decision ratio, compared with the baseline counterparts.

Trust-Threshold Based Routing in Delay Tolerant Networks

We propose a trust-threshold based routing protocol for delay tolerant networks, leveraging two trust thresholds for accepting recommendations and for selecting the next message carrier for message forwarding. We show that there exist optimal trust threshold values under which trust-threshold based routing performs the best in terms of message delivery ratio, message delay and message overhead. By means of a probability model, we perform a comparative analysis of trust-threshold based routing against epidemic, social-trust-based and QoS-trust-based routing. Our results demonstrate that trust-threshold based routing operating under proper trust thresholds can effectively trade off message delay and message overhead for a significant gain in message delivery ratio. Moreover, our analysis helps identify the optimal weight setting to best balance the effect of social vs. QoS trust metrics to maximize the message delivery ratio without compromising message delay and/or message overhead requirements.