Multiagent and Grid Systems

Cloud computing provides excellent quality computing services with lower cost and better performance. The cloud services which are provided by the trusted third party encourage the customers and organizations to move their activities to the cloud. While moving towards the concept of on-demand service, resource pooling and shifting everything on the distributive environment, security is the major obstacle for this new dreamed vision of computing capability. Over the past several years, many security mechanisms have been proposed for protecting outsourced data. In this paper, we present a consolidated survey of various security issues and threats pertaining to data in cloud computing. Further, we analyzed security challenges in cloud based on its delivery models. We also discussed the component based classification of major security concerns and recent counter measures that present in the literature with the intention of providing an in-detail understanding of cloud computing security needs. In addition, a brief outlook of security precautions adopted by cloud service providers and various Intrusion Detection/Prevention Systems is presented.

One of the current discussions concerning cloud computing environments involves the issue of failure prediction that influences the delivery of on-demand services through the Internet. Proactive failure prediction techniques play an important role in reducing undesirable consequents produced by failures within high performance systems. Accordingly, this study aims at proposing a threshold sensitive by using support vector machine to create an efficient mechanism for predicting failure within cloud environments. The new approach can operationally avoid system failures for each host based on log file which include features such as CPU utilization, RAM, and bandwidth, etc. In comparison to the base research, the findings demonstrated that the presented method could better reduce the percent of migrations about 76.19% proactively when the failure threshold level was 70%.

Planning agents evolving in dynamic and complex environments need to continually plan their tasks and to monitor the evolution of its execution in order to deal with unexpected situations. To face this challenge, we proposed, in previous works, HPINet (Hierarchical-Task-Petri-Net) and SHPINet (HPINet with synchronization), models that can be used to represent plans less sensitive to execution contexts, and that support automatic verification. In this paper, we aim to propose computational techniques to verify some keys properties, such as soundness, of executing partial plans by analyzing their abstract level of representation. We especially focus on the some theorems and their corresponding proofs about the soundness of plan.

Today, data replication is widely used in large-scale systems such as data grids to meet the requirements and challenges of managing these huge amounts of data. Indeed, replication is used to reduce the data access cost and access latency, to improve availability and performance, and to ensure reliability in grids. Most proposed replication strategies deal read-only case when accessing data, few approaches studies data consistency when the updates are allowed in data grids. In this paper, we present a contribution using a quorum-based management of replicas approach to maintain the consistency of these replicas, whose goal is to minimize quorum sizes to decrease replication costs and improve performances.

In a data grid, nodes have a limited storage space and cannot accommodate all the replicas they need. Therefore, data replication is used to copy only important replicas that may be requested in the near future. In this paper, a dynamic data replication strategy is implemented in order to increase the number of requests served locally and reduce both the total elapsed time and total bandwidth consumption. This strategy is based on Bandwidth Hierarchy based Replication (BHR) and modified BHR strategies, but superior to them. This is because of the features this strategy has. This strategy selects a region header in each region based on a modified version of closeness centrality and stores all the replicas in the data grid in the region header. Regarding the other nodes in the region, only important replicas will be copied to them based on their number of requests per mega bit (NoRpmb) that shows how much important the replica is in relation to its size.

In multi-agent systems, the yellow pages service is very important for agents to be able to interact with each other. The more the number of agents is high, the more performance degradation will result, due to the overload of requests sent to central yellow pages. This issue didn’t get much attention from researchers despite its importance. The proposed approach for solving this scalability issue is based on the aspect-oriented paradigm. An aspect was used to play the roles of a replicator and a distributor of requests to several new yellow pages. The use of aspect-oriented programming simplifies the implementation, reduces the maintenance effort and offers a good reusability of the proposed solution. The approach is validated on three JADE applications and evaluated on five different machines. Results, which are very promising, show a significant scalability and performance improvement of the yellow pages service especially on Linux operating system.