Azad H. Azadmanesh

A graph based model for survivability applications

Many problems found in standard security and survivability applications can be transformed into graph and scheduling problems, thereby opening up the problems to a wealth of potential solutions or knowledge of limitations, infeasibility, scalability or intractability. This paper introduces a model to aid in the design, analysis, or operations of applications with security and survivability concerns. Specifically, a five step model is presented that transforms such applications into a parameterized graph model that, together with model abstraction and representations, can be the basis for solutions derived from graph and scheduling algorithms. A reverse transformation translates the solutions back to the application domain. The model is demonstrated using migratory agent security and fault-tolerant agreement and their transformation into chain constrained and group scheduling problems, respectively.

Architecture-based reliability analysis of web services in multilayer environment

The reliability analysis of web services is often focused on the web service components, ignoring the impact of the middleware located beneath the web services. A service-based software system is a multilayered system that includes the web service (WS), shared resources, and the hosting application server (AS). It is conjectured that the reliability prediction of the web services is improved if the reliability model accounts for such underlying layers. The initial experiment illustrates that the AS and shared resources can impact the overall reliability of web services greatly. This observation is demonstrated by simulating the interaction between a web service and the AS.

Scheduling issues in survivability applications using hybrid fault models

This research addresses scheduling issues in networked computer systems with survivability requirements, i.e. systems in which essential services must survive malicious acts. In order to achieve survivability based on spatial redundancy, agreement algorithms are needed as a mechanism to consolidate results of individual replicas. The potentially enormous overhead associated with communication and voting schemes of the algorithms put unique burdens on the scheduler as the efficiency of scheduling determines the suitability of the agreement algorithm. This paper derives agreement task graphs, representing computations, and inter-process communication based on phantom tasks. Task graph primitives are identified and it is shown how their scheduling directly influences the performance of the agreement algorithm. Finally, the notion of dynamic k-of-N precedence is introduced and its impact on resource reclaiming for early stopping algorithms is discussed.

Survivable Data Aggregation in Multiagent Network Systems with Hybrid Faults

With respect to the data aggregation (DA) survivability, the research in partially connected networks (PCN) is limited. This study investigates the DA survivability for PCNs in synchronous systems in the presence of hybrid fault modes, with the following in mind: 1) agents that run on network nodes use messages from their immediate neighbors only, i.e., no relay of information is allowed, 2) hybrid fault models are assumed; therefore, the DA algorithm is flexible to be tuned for various fault settings, 3) impacts of faults and threats rather than their sources are considered; hence, significant number of misbehaviors are reduced to a small number of fault modes, and 4) the network can tolerate any number of faults as long as the maximum number of faults encountered by each agent does not exceed a predefined threshold. The results show that the upper bound on the number of rounds to reach global convergence (agreement) and the asymptotic convergence per round depend on intertwined parameters such as precision of convergence, node degree, number of agents in the network, level of fault tolerance, and the network diameter. It is illustrated that the network-diameter has the most impact on the speed to reach global convergence.

Data aggregation in partially connected networks

With the diverse new capabilities that sensor and ad hoc networks can provide, applicability of data aggregation is growing. Data aggregation is useful in dealing with multi-value domain information, which often requires approximate agreement decisions among nodes. In contrast to fully connected networks, the research on data aggregation for partially connected networks is very limited. This is due to the complexity of formal proofs and the fact that a node may not have a global view of the entire network, which makes it difficult to attain the convergence properties. The complexity of the problem is compounded in the presence of message dropouts, faults, and orchestrated attacks. By exploiting the properties of Discrete Markov Chains, this study investigates the data aggregation problem for partially connected networks to obtain: the number of rounds of message exchanges needed to reach a network-convergence, the average convergence rate in a round of message exchange, and the number of rounds required to reach a stationary-convergence.

Data Aggregation in Static Adhoc Networks

This research is concerned with the data aggregation (DA) algorithms in wireless static networks, where host mobility is low or not provided and the number of nodes is fixed. The DA problem is investigated in the presence of omission faults, which can be a common type of failure in wireless communication. It is shown that, in the worst case, the number of rounds of message-exchange needed to reduce the diameter of values held by the hosts in the network is half the maximum network diameter. The research also obtains the upper bound on the number of rounds of message-exchange to reach the stationary-convergence, i.e. the difference between the agreed upon values among the hosts is within a predefined tolerance.

Architectural reliability analysis of framework-intensive applications: A web service case study

Abstract A novel methodology for modeling the reliability and performance of web services (WSs) is presented. To present the methodology, an experimental environment is developed in house, where WSs are treated as atomic entities but the underlying middleware is partitioned into layers. WSs are deployed in JBoss AS. Web service requests are generated to a remote middleware on which JBoss runs, and important performance parameters under various configurations are collected. In addition, a modularized simulation model in Petri net is developed from the architecture of the middleware and run-time behavior of the WSs. The results show that (1) the simulation model provides for measuring the performance and reliability of WSs under different loads and conditions that may be of great interest to WS designers and the professionals involved; (2) configuration parameters have substantial impact on the overall performance; (3) the simulation model provides a basis for aggregating the modules (layers), nullifying modules, or to include additional aspects of the WS architecture; and (4) the model is beneficial to predict the performance of WSs for those cases that are difficult to replicate in a field study.

Security and survivability of networked systems

Summary form only given. This minitrack was organized as a research forum to pursue the interrelationships between security, survivability, and reliability in large, non-trivial, networked computer systems. The papers are divided into two sessions, separated by a presentation on Security Trends and Initiatives at the U.S. National Institute of Standards and Technology (NIST). The three papers in the first session address ways of measuring and testing security properties in software systems. The NIST presentation provides a forum for learning about some of the U.S. governments security and survivability research initiatives. In the last paper session, we have combined a paper on ad-hoc sensor networks with two papers from the minitrack on Secure and Survivable Mobile Agents.

Sensor localization for indoor wireless sensor networks

Although numerous solutions have been proposed to the sensor area localization problem, most of them are aimed at two-dimensional (2D) planes rather than the three-dimensional (3D) scenarios in real world applications. This study presents a novel approach to indoor localization of a mobile object that is equipped with sensors and cameras by utilizing Building Information Modeling (BIM) and 3D stereo image measurements. Based on some experiments conducted, the proposed scheme has shown its potential to be useful in real world applications.

VANET clock synchronization for resilient DSRC safety applications

Vehicular Ad Hoc Networks (VANET) are the fastchanging networks for connected vehicles, in which Vehicle- to-Vehicle and Vehicle-to-Infrastructure communication are the basis for technologies aiming at reducing accidents and improving operation. DSRC Safety Applications, designed to assist drivers in order to avoid accidents, might be subjected to malicious attacks, such as GPS time spoofing attacks, which attempt to prevent time synchronization between vehicles. Failure of the centralized GPS-based clock synchronization has the potential to cause safety applications to fail. Therefore, decentralized clock synchronization can be a valuable approach for augmenting GPS- based clock synchronization. In this paper, a decentralized clock synchronization protocol for VANET is presented. The proposed protocol, based on approximate agreement, does not require any extra hardware nor modifications of any standards. The protocol was simulated using NS-3, and the results were analyzed and compared with previous synchronization protocols. The benefits of the proposed clock synchronization algorithm are higher resilience of safety applications to GPS spoofing attacks and when GPS signals are not available, such as in urban cities.