4,227 research outputs found
Autonomic Management of Maintenance Scheduling in Chord
This paper experimentally evaluates the effects of applying autonomic
management to the scheduling of maintenance operations in a deployed Chord
network, for various membership churn and workload patterns. Two versions of an
autonomic management policy were compared with a static configuration. The
autonomic policies varied with respect to the aggressiveness with which they
responded to peer access error rates and to wasted maintenance operations. In
most experiments, significant improvements due to autonomic management were
observed in the performance of routing operations and the quantity of data
transmitted between network members. Of the autonomic policies, the more
aggressive version gave slightly better results
Achieving Robust Self-Management for Large-Scale Distributed Applications
Autonomic managers are the main architectural building blocks for constructing self-management capabilities of computing systems and applications. One of the major challenges in developing self-managing applications is robustness of management elements which form autonomic managers. We believe that transparent handling of the effects of resource churn (joins/leaves/failures) on management should be an essential feature of a platform for self-managing large-scale dynamic distributed applications, because it facilitates the development of robust autonomic managers and hence improves robustness of self-managing applications. This feature can be achieved by providing a robust management element abstraction that hides churn from the programmer.
In this paper, we present a generic approach to achieve robust services that is based on finite state machine replication with dynamic reconfiguration of replica sets. We contribute a decentralized algorithm that maintains the set of nodes hosting service replicas in the presence of churn. We use this approach to implement robust management elements as robust services that can operate despite of churn. Our proposed decentralized algorithm uses peer-to-peer replica placement schemes to automate replicated state machine migration in order to tolerate churn. Our algorithm exploits lookup and failure detection facilities of a structured overlay network for managing the set of active replicas. Using the proposed approach, we can achieve a long running and highly available service, without human intervention, in the presence of resource churn. In order to validate and evaluate our approach, we have implemented a prototype that includes the proposed algorithm
Broadcasting in Prefix Space: P2P Data Dissemination with Predictable Performance
A broadcast mode may augment peer-to-peer overlay networks with an efficient,
scalable data replication function, but may also give rise to a virtual link
layer in VPN-type solutions. We introduce a simple broadcasting mechanism that
operates in the prefix space of distributed hash tables without signaling. This
paper concentrates on the performance analysis of the prefix flooding scheme.
Starting from simple models of recursive -ary trees, we analytically derive
distributions of hop counts and the replication load. Extensive simulation
results are presented further on, based on an implementation within the OverSim
framework. Comparisons are drawn to Scribe, taken as a general reference model
for group communication according to the shared, rendezvous-point-centered
distribution paradigm. The prefix flooding scheme thereby confirmed its widely
predictable performance and consistently outperformed Scribe in all metrics.
Reverse path selection in overlays is identified as a major cause of
performance degradation.Comment: final version for ICIW'0
Systematizing Decentralization and Privacy: Lessons from 15 Years of Research and Deployments
Decentralized systems are a subset of distributed systems where multiple
authorities control different components and no authority is fully trusted by
all. This implies that any component in a decentralized system is potentially
adversarial. We revise fifteen years of research on decentralization and
privacy, and provide an overview of key systems, as well as key insights for
designers of future systems. We show that decentralized designs can enhance
privacy, integrity, and availability but also require careful trade-offs in
terms of system complexity, properties provided, and degree of
decentralization. These trade-offs need to be understood and navigated by
designers. We argue that a combination of insights from cryptography,
distributed systems, and mechanism design, aligned with the development of
adequate incentives, are necessary to build scalable and successful
privacy-preserving decentralized systems
Performance analysis of structured peer-to-peer overlays for mobile networks
Distributed Hash Table (DHT) based Peer-to-Peer (P2P) overlays have been widely researched and deployed in many applications such as file sharing, IP telephony, content distribution and media streaming applications. However, their deployment has largely been restricted to fixed, wired networks. This is due to the fact that supporting P2P overlays on wireless networks such as the public mobile data network is more challenging due to constraints in terms of data transmissions on cellular networks, limited battery power of the handsets and increased levels of node churn. However, the proliferation of smartphones makes the use of P2P applications on mobile handsets very desirable. In this paper, we have analysed and evaluated the performance and efficiency of five popular DHT based structured P2P overlays (Chord, Pastry, Kademlia, Broose and EpiChord) under conditions as commonly experienced in public mobile data networks. Our results show that the conditions in mobile networks, including a high churn rate and the relatively low bandwidth availability is best matched by Kademlia and EpiChord. These overlays exhibit a high lookup success ratio and low hop count while consuming a moderate amount of bandwidth. These characteristics make these two overlays suitable candidates for use in mobile networks
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