Searching in Unstructured Overlays Using Local Knowledge and Gossip

This paper analyzes a class of dissemination algorithms for the discovery of distributed contents in Peer-to-Peer unstructured overlay networks. The algorithms are a mix of protocols employing local knowledge of peers' neighborhood and gossip. By tuning the gossip probability and the depth k of the k-neighborhood of which nodes have information, we obtain different dissemination protocols employed in literature over unstructured P2P overlays. The provided analysis and simulation results confirm that, when properly configured, these schemes represent a viable approach to build effective P2P resource discovery in large-scale, dynamic distributed systems.Comment: A revised version of the paper appears in Proc. of the 5th International Workshop on Complex Networks (CompleNet 2014) - Studies in Computational Intelligence Series, Springer-Verlag, Bologna (Italy), March 201

Consistency in scalable systems

[EN] While eventual consistency is the general consistency guarantee ensured in cloud environments, stronger guarantees are in fact achievable. We show how scalable and highly available systems can provide processor, causal, sequential and session consistency during normal functioning. Failures and network partitions negatively affect consistency and generate divergence. After the failure or the partition, reconciliation techniques allow the system to restore consistency.This work has been supported by EU FEDER and Spanish MICINN under research grants TIN2009-14460-C03-01 and TIN2010-17193.Ruiz Fuertes, MI.; Pallardó Lozoya, MR.; Muñoz-Escoí, FD. (2012). Consistency in scalable systems. En On the Move to Meaningful Internet Systems: OTM 2012. Springer Verlag (Germany). 7566:549-565. https://doi.org/10.1007/978-3-642-33615-7_7S5495657566Ahamad, M., Bazzi, R.A., John, R., Kohli, P., Neiger, G.: The power of processor consistency. 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ACCEPTED MANUSCRIPT On the Interconnection of Message Passing Systems Abstract

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A topology self-adaptation mechanism for efficient resource location

This paper introduces a novel unstructured P2P system able to adapt its overlay network topology to the load conditions. The adaptation is performed by means of a mechanism which is run by the nodes in the network in an autonomous manner using only local information, so no global coordinator is needed. The aim of this adaptation is to build an efficient topology for the resource discovery mechanism performed via random walks. We present the basis of the adaptation mechanism, along with some simulation results obtained under different conditions. These results show that this system is efficient and robust, even in front of directed attacks. 1

Decoupled Interconnection of Distributed Memory Models

In this paper we present a framework to formally describe and study the interconnection of distributed shared memory systems. In our models we minimize the dependencies between the original systems and the interconnection system (that is, they are decoupled) and consider systems implemented with invalidation and propagation

Distributed resource search in self-organising networks

Virtual Organisations (VO) have emerged as an important field of study in the area of Multi Agent Systems (MAS). A VO consists of a number of members that share preferences or goals with the aim of exploiting the available resources and providing better services than a single member would be able to. In this paper, VOs have been used as a way to cluster heterogeneous agents which have semantically close resources together. A VO-based resource search protocol has been developed with search message routing techniques that have been used to forward resource search messages among VOs instead of individual agents. A decision making component has been added to the agent's body to facilitate the process of maintaining the VO's functionality. Different scenarios have been studied to deal with situations which might affect the VO's work-flow. The proposed solutions have been implemented and tested in a simulated environment. The simulation results have shown a significant improvement in the search results in terms of the quality of matching, the required time to find the requested resources and the success ratio of requests. © 2013 Springer-Verlag