9,080 research outputs found
A Lightweight Approach for Improving the Lookup Performance in Kademlia-type Systems
Discovery of nodes and content in large-scale distributed systems is
generally based on Kademlia, today. Understanding Kademlia-type systems to
improve their performance is essential for maintaining a high service quality
for an increased number of participants, particularly when those systems are
adopted by latency-sensitive applications.
This paper contributes to the understanding of Kademlia by studying the
impact of \emph{diversifying} neighbours' identifiers within each routing table
bucket on the lookup performance. We propose a new, yet backward-compatible,
neighbour selection scheme that attempts to maximize the aforementioned
diversity. The scheme does not cause additional overhead except negligible
computations for comparing the diversity of identifiers. We present a
theoretical model for the actual impact of the new scheme on the lookup's hop
count and validate it against simulations of three exemplary Kademlia-type
systems. We also measure the performance gain enabled by a partial deployment
for the scheme in the real KAD system. The results confirm the superiority of
the systems that incorporate our scheme.Comment: 13 pages, 8 figures, conference version 'Diversity Entails
Improvement: A new Neighbour Selection Scheme for Kademlia-type Systems' at
IEEE P2P 201
Analysis of a Reputation System for Mobile Ad-Hoc Networks with Liars
The application of decentralized reputation systems is a promising approach
to ensure cooperation and fairness, as well as to address random failures and
malicious attacks in Mobile Ad-Hoc Networks. However, they are potentially
vulnerable to liars. With our work, we provide a first step to analyzing
robustness of a reputation system based on a deviation test. Using a mean-field
approach to our stochastic process model, we show that liars have no impact
unless their number exceeds a certain threshold (phase transition). We give
precise formulae for the critical values and thus provide guidelines for an
optimal choice of parameters.Comment: 17 pages, 6 figure
Proceedings of International Workshop "Global Computing: Programming Environments, Languages, Security and Analysis of Systems"
According to the IST/ FET proactive initiative on GLOBAL COMPUTING, the goal is to obtain techniques (models, frameworks, methods, algorithms) for constructing systems that are flexible, dependable, secure, robust and efficient.
The dominant concerns are not those of representing and manipulating data efficiently but rather those of handling the co-ordination and interaction, security, reliability, robustness, failure modes, and control of risk of the entities in the system and the overall design, description and performance of the system itself.
Completely different paradigms of computer science may have to be developed to tackle these issues effectively. The research should concentrate on systems having the following characteristics: • The systems are composed of autonomous computational entities where activity is not centrally controlled, either because global control is impossible or impractical, or because the entities are created or controlled by different owners.
• The computational entities are mobile, due to the movement of the physical platforms or by movement of the entity from one platform to another.
• The configuration varies over time. For instance, the system is open to the introduction of new computational entities and likewise their deletion.
The behaviour of the entities may vary over time.
• The systems operate with incomplete information about the environment.
For instance, information becomes rapidly out of date and mobility requires information about the environment to be discovered.
The ultimate goal of the research action is to provide a solid scientific foundation for the design of such systems, and to lay the groundwork for achieving effective principles for building and analysing such systems.
This workshop covers the aspects related to languages and programming environments as well as analysis of systems and resources involving 9 projects (AGILE , DART, DEGAS , MIKADO, MRG, MYTHS, PEPITO, PROFUNDIS, SECURE) out of the 13 founded under the initiative. After an year from the start of the projects, the goal of the workshop is to fix the state of the art on the topics covered by the two clusters related to programming environments and analysis of systems as well as to devise strategies and new ideas to profitably continue the research effort towards the overall objective of the initiative.
We acknowledge the Dipartimento di Informatica and Tlc of the University of Trento, the Comune di Rovereto, the project DEGAS for partially funding the event and the Events and Meetings Office of the University of Trento for the valuable collaboration
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