Conclusion & Future Work

Transcription

1 CHAPTER 7 Conclusion & Future Work 7.1 Conclusion This chapter presents the conclusions which have been derived fulfilling the objective defined in the beginning of chapter 1. The Architecture for Resource Management in Global Grids was introduced with an aim to handle Distributed Heterogeneous Resources Reputation paradigm which further support in managing Resource Management for Grid Computing environments. A reliable and efficient Grid based upon the Trust factor of each & every Grid Resource being integrated in Grid as per the Consumer application requisite, is attained through a Decentralized Grid Reputation-based Trust Model called GridPeerTrust. The merits of the proposed Architecture are obvious from; its comparisons made with existing/prevalent Trust Models. Following conclusions have been achieved which are valuable contributions of the Research:- 1. Pre-standardization of Reputation models for Grid Environment Pre-standardization based on the existing Trust and/or Reputation models that had arisen in the last few years in Grid Environment concluded key processes in common such as gathering information, trust decay, rewarding or punishing. Providing recommendations benefited distributed systems such as Grid Environment for more critic and unavoidable trust and reputation mechanism, specifically in context to Grid Environment. 2. Trust-based Architecture for Global Grids A Secured Grid Resource Management for Global Grids by addition of a Trust-based 139

2 Layer assured the Trust worth of the Grid Resource and consequently the Trust worth of the Grid, on whole, as it entered the commercial arena wherein it promised to help the Grid Consumer in Decision Making, as the system offered only those Gird Resources which assure of a high degree of Trust Relationship of Grid Resource provider. 3. Reputation-based Trust Model The GridPeerTrust, Reputation-based Trust Model allowed Grid Client Applications (e.g. resource brokers, schedulers and monitoring toolkits) to control the Trust and Reputation evaluation of Resource Provider. The Trust Model, called for computing and comparing the Trust values of entities complied through a transaction-based Feedback System and concluded a decentralized implementation of this model in Global Grid network. GridPeerTrust combined various important aspects related to the management of Trust and Reputation in Grid environment such as: (i) Feedback a Grid Resource Provider (entity) receives from Grid Resource Consumer; (ii) Credibility of the recommendations given by Grid Resource Consumer; (iii) Total number of transaction of a Grid Entity, Decay Factor and Trust Context Factor. It is these very aspects which appraise the worth of Grid in the best possible way for Application success as well as in Consumer satisfaction terms. 4. Grid Resource Reputation Trust Manager The Reputation Trust Manager processed the reputation evaluation criteria denoted by the Trust Evaluation Process and calculated Trust level values for a Grid Resource or a set of Resources. The implementation of Trust Manager for each grid entity helped in implementing Reputation-based Trust Model in a decentralized manner. 5. Countering Feedback Security Threats This contribution is the refinement of the Trust Framework to minimize the potential vulnerabilities and security threats in the Reputation System itself. The proposed 140

3 Reputation Model through its defense mechanisms enable the framework to resilient to several security threats including Malicious Individuals, Malicious Collectives, Malicious Collectives with Camouflage, Malicious Spies, Sybil Attack, Man in the Middle Attack, Driving Down the Reputation of a Reliable Entity, Partially Malicious Collectives, Malicious Pre-trusted Entity. Conclusively, this research has significantly attained its aims and objective by demonstrating how the reputation-based Trust Model optimized the Resource Management process in Global Grids. This was demonstrated in the testbed experiments where GridPeerTrust managed to employ computing resources which embrace the parameters stipulated by the trust evaluation process of the assigned job and consequently managed to mitigate the number of malicious entities in the Global Grid and constitutes as an important milestone toward the evolution from failure tolerant research-oriented Grids into mission critical one. The reputation-based Trust Model gained further strength with its ability to adapt to specific job requirements and provide an optimization of the reputation evaluate on process by basing it on multiple Trust context characteristics (e.g. availability, reliability). On a broader scale it can be implied that reputation-based Trust Model, besides Global Grids, has the potential to be applied to different computing paradigms such as Web services, XML-RPC, and other SOA technologies, which normally involve service consumers and producers negotiating through bilateral agreements. On the other hand, the limitations of the reputation-based Trust Model include: (i) amplification of computation overhead, as it requires an extra step of stipulating reputation Trust evaluation process; (ii) message complexity increases, as the reputation query increases in size due to the addition of the TDS; and (iii) a computational overhead due to the processing of multiple QoS factors and a complex trust evaluation process. Existing reputation-based Trust Models offer an adequate level of confidence for most types of users and computational tasks and are generally favored for their simplicity. On the other hand, this reputation-based based Trust Model targets specific scenarios where explicit stipulation of reputation evaluation criteria is required. From its point of view, it 141

4 simply attempts to optimise the Resource Management by adapting it to specific type of jobs and user requirements. 7.2 Future Work The work of described in this thesis has also identified a number of areas for future research. These are listed as follows: 1. Automatic Feedback Management: This aspect is currently absent from the reputationpolicy based trust model and considered essential. The feedback ratings should be supplied automatically by monitoring toolkits and it should take into account different factors, such as the difference between the actual service provided and the level of service guaranteed in the SLA contract and length of experience the resource broker achieved with the evaluated resource (shorter length implies greater feedback). In addition, the feedback ratings should be supplied for each opinion aspect in the TDS. For example, if the resource broker stipulated availability and reliability as quality factors, it should supply ratings for these two aspects on transaction completion. 2. Self-Monitoring Reputation-Policy Trust Model: Several improvements and additions can be made to the trust model. For example, at current state the, only historical rating feedbacks are considered as valid trust source for evaluation. The model can be expanded with real time performance data (via monitoring toolkits) as well as trust prediction models which would aim to assess the performance of a resource at a certain point in the future. This functionality can be proven useful for future scheduled jobs in which solely relying on historical information would not be sufficient. 3. Trust Management issues in Cloud Computing: Cloud computing has been attracting the attention of several researchers both in the academia and the industry as it provides many opportunities for organizations by offering a range of computing services. Before cloud computing to become acceptable to everybody both the enterprises and individuals, several issues have to be solved. One of the most important aspects that need to be paid 142

5 special attention is the cloud security. Trust management is one of the important components in the cloud security that needs special attention. The trust management systems proposed for cloud computing by various researchers have been studied with special emphasis their capability, their applicability in practical heterogonous cloud environment and their implementabilty. 143