Mujtaba Khambatti

Structuring Peer-to-Peer Networks Using Interest-Based Communities

Interest-based communities are a natural arrangement of distributed systems that prune the search space and allow for better dissemination of information to participating peers. In this paper, we introduce the notion of peer communities. Communities are like interest groups, modeled after human communities and can overlap. Our work focuses on providing efficient formation, discovery and management techniques that can be implemented to constantly changing community structures. We provide a mechanism to generate realistic peer-to-peer network topologies that can be used in simulations that evaluate the operation of our algorithms. Our experiments show how searching the peer-to-peer network can take advantage of peer communities to reduce the number of messages and improve the quality of search results.

A role-based trust model for peer-to-peer communities and dynamic coalitions

Although P2P systems are usually used for information exchange between peers, they have either protected peers anonymity, or required transacting peers to trust each other implicitly. Both these approaches are vulnerable to attacks by malicious peers who could abuse the P2P system to spread viruses, incorrect, or damaging information. Here, we propose an approach for trust management in P2P systems. We introduce an optimistic role-based model for trust amongst peers and show that it is scalable, dynamic, revocable, secure and transitive. Our proposed solution permits asymmetric trust relationships that can be verified by any peer in the system through a simple, low-cost algorithm. We introduce a metric known as iComplex that combines a peers trust value for each of its roles into a single, relative, probabilistic guarantee of trust. Finally, we discuss how our trust model allows peers to revoke relationships with malicious peers, and the nonrepudiation of peer relations. We use simulations to illustrate the trust value distribution amongst peers in the network. Our analysis and experiments demonstrates the low-cost involved to verify and validate trust values. Lastly, we establish the effectiveness of using sum as the aggregation function to combine trust values of a peer.

Reliability Assessment of Mass-Market Software: Insights from Windows Vista®

Assessing the reliability of mass-market software (MMS), such as the Windowsreg operating system, presents many challenges. In this paper, we share insights gained from the Windows Vistareg and Windows Vistareg SP1 operating systems. First, we find that the automated reliability monitoring approach, which periodically reports reliability status, provides higher quality data and requires less effort compared to other approaches available today. We describe one instance in detail: the Windows reliability analysis component, and illustrate its advantages using data from Windows Vista. Second, we show the need to account for usage scenarios during reliability assessments. For pre-release versions of Windows Vista and Vista SP1, usage scenarios differ by 2-4X for Microsoft internal and external samples; corresponding reliability assessments differ by 2-3X. Our results help motivate and guide further research in reliability assessment.