Survivability And Its Evaluation Methods In Mobile Ad Hoc Networks

Survivability refers to the ability of a network system to fulfill critical services in a timely manner to end users in the presence of faults and/or attacks. It is not only a fundamental property of network, but also an important metric to evaluate the survivability on politics, military, and economics in a country. Nowadays survivability is an important research direction on network and information security.Even though researches on mobile ad hoc networks (MANETs) go deeper and their applications get wider, MANETs are still vulnerable to various faults as well as attacks due to their characteristics, resulting in research on the survivability more challenging. How to conduct a quantitative analysis on the survivability, and how to improve the survivability of the system are key issues on survivability research in MANETs. In order to solve the above problems, evaluation model, survivable mechanism and survivable routing protocol, are proposed with different views, different methods and techniques in this dissertation. Innovations of this dissertation are as follows:(1) We propose a quantitative evaluation model on survivability for node fault oriented. First, the model takes various types of faults into account for survivability modeling, and then uses the continuous time Markov chain (CTMC) to describe the survivability of MANETs in a precise manner. Second, we introduce the reliability theory to perform quantitative evaluation for survivability on routing protocols in large-scale MANETs, such as segment-by-segment routing (SSR), multipath-based segment-by-segment routing (M-SSR), and cluster-based multipath dynamic source routing (CMDSR). Finally, the analytic results show the effectiveness of our approach through experiments.(2) We present a quantitative evaluation model on survivability for node misbehavior oriented. The purpose of this method is to achieve the quantitative analysis on survivability in 3D MANETs, in the presence of attacks of nodes, through modeling on node misbehaviors and analysis of 3D network connectivity. First, we model the node misbehaviors by using semi-Markov process, and derive the node minimum degree of 3D MANETs. Second, we develop an effective approach to analyze k-connectivity of 3D MANETs, based on the model of isolated node problem. Third, we achieve a mathematical description of network survivability for the k-connected maintenance, through analyzing their connectivity in 3D MANETs caused by node misbehaviors. Finally, the analytic results show the effectiveness and correctness of our approach through experiments.(3) According to the quantitative evaluation on survivability, we propose a dynamic trust mechanism (DTM) based on multi-constraints and collaborative filtering in MANETs in order to improve the system survivability and to ensure secure communication among nodes. The main idea of DTM is to introduce a trust updating algorithm with multi-constraints (time aging factor ensures that the trust fades with time; rewards factor ensures that good peers deserve to be rewarded; and penalty factor ensures that the malicious deserve to be punished) to assess the direct trust among nodes. And the false recommendation is prevented by adopting collaborative filtering technique to evaluate recommendation trust. The analytic results show that DTM can compute trust between nodes more precisely than Bayesian model through performance analysis.(4) We present a trusted routing protocol based on DTM, and the object is to further validate the effectiveness of the DTM and to improve the system survivability. First, we develop a DTM-DSR protocol based on DTM by extending DSR, in which a node makes a routing decision based on the trust value of its neighboring nodes. Second, the DTM-DSR can prevent malicious nodes to forward data packets by establishing trusted route through the trust value of nodes along the path. Finally, the effectiveness of our approach is validated through extensive simulations. The simulation results show that DTM-DSR improves network performance more effectively than DSR and Bayesian-DSR protocols.Our research on network survivability and its evaluation is basic in this area. Some important work has been done in this dissertation which contributes to addressing some key research issues in the area of survivability and its evaluation in MANETs, which produces some theoretical values in promoting the research on network survivability and some practical values in guiding the network design and in improving network survivability.