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

H-P2PSIP: Interconnection of P2PSIP domains for Global Multimedia Services based on a Hierarchical DHT Overlay Network

The IETF P2PSIP WG is currently standardising a protocol for distributed mul- timedia services combining the media session functionality of SIP and the decentralised distribution and localisation of resources in peer-to-peer networks. The current P2PSIP scenarios only consider the infrastructure for the connectivity inside a single domain. This paper proposes an extension of the current work to a hierarchical multi-domain scenario: a two level hierarchical peer-to-peer overlay architecture for the interconnection of different P2PSIP domains. The purpose is the creation of a global decentralised multimedia services in enterprises, ISPs or community networks. We present a study of the Routing Performance and Routing State in the particular case of a two-level Distributed Hash Table Hierarchy that uses Kademlia. The study is supported by an analytical model and its validation by a peer-to-peer simulator.En prens

A Probabilistic Analysis of Kademlia Networks

Kademlia is currently the most widely used searching algorithm in P2P (peer-to-peer) networks. This work studies an essential question about Kademlia from a mathematical perspective: how long does it take to locate a node in the network? To answer it, we introduce a random graph K and study how many steps are needed to locate a given vertex in K using Kademlia's algorithm, which we call the routing time. Two slightly different versions of K are studied. In the first one, vertices of K are labelled with fixed IDs. In the second one, vertices are assumed to have randomly selected IDs. In both cases, we show that the routing time is about c*log(n), where n is the number of nodes in the network and c is an explicitly described constant.Comment: ISAAC 201

Increasing competitiveness of the construction sector by adopting innovative clustering

Companies in today's world need to become and stay competitive. This means, among other things, that they have to create new ideas and turn them into innovative products and processes. Appropriate innovation management strategies, including creation of various kinds of alliances with other business entities, need to be adopted within the company. Clustering is one of such possibilities. The paper discusses the main features of clusters and the benefits for their members; in addition, it identifies specific features of the construction sector that require specific approaches to establish a cluster.\ud The methodology Innovative Cluster Model with 3x3x3 mail elements (ICM333) is proposed and used to initiate and develop a cluster in the construction sector. In the cluster development three stages are identified: emergence, development and maturity of the cluster. Actions associated with these three stages tackle four areas (in each stage): rationale, organization, resources, and implementation. All areas are thoroughly elaborated and discussed in the paper. In the first step, the emerging cluster, the key element is identification, assessment and dissemination of development opportunities. It can run parallel with the cluster initiation, which is followed by the operation. Within the steps to be taken in the stage of the developing cluster, visions nad the goals have to be defined first, followed by the definition of the cluster organisation. The mature cluster stage has to focus on performance measurement and management, and take appropriate measures to garantee its sustainability and adequate innovative character.\ud Implementation of the proposed cluster development methodology has the potential of greatly facilitating the betterment of a construction sector in a particular country. It can be a valuable tool, when available to policymakers, chambers of commerce and trade, and other stakeholders that wish to foster the development of such clusters.\ud The paper reports on the results of the 7th Framework project FP7-REGIONS-2007-1 RegCon – Support Action for Innovation Driven Clusters in Construction.\u

Drenažna mreža otpadnih voda: analiza radnog okruženja

In the city of Beja, Portugal, there is an infrastructure for the conduction of wastewater for treatment, this infrastructure is subject to periodic and systematic rehabilitation and maintenance and can still be used by authorities and even by other companies. Each manhole is a potential confined space with all the constraints and problems that they usually present. A thorough and systematic analysis of the atmosphere inside the manholes of the wastewater drainage system was made to know the respective risks and hazards to all subjects exposed, throughout the East part of the city, from the gases produced and in these installations. The data collection was carried out in two different periods when the network presented minimum flows in normal operation. The flows were considered minimum after the reading of the flowmeters installed in the measurement areas indicated it.Grad Beja u Portugalu ima infrastrukturu za odvođenje otpadnih voda na daljnju obradu. Ta se infrastruktura povremeno obnavlja i održava a radove obavlja gradska uprava ili druge tvrtke. Svaki šaht je potencijalno ograničen prostor koji predstavlja razne teškoće. U istočnom dijelu grada učinjena je sustavna analiza zraka u šahtovima odvodnog sustava kako bi se utvrdili rizici i opasnosti za osobe izložene plinovima u takvim instalacijama. Podaci su prikupljani u dva navrata kad je mreža normalno radila i bila najmanje opterećena protokom. Protoci su se smatrali minimalnima kad su mjerni instrumenti za bilježenje protoka tako pokazali

Drenažna mreža otpadnih voda: analiza radnog okruženja

In the city of Beja, Portugal, there is an infrastructure for the conduction of wastewater for treatment, this infrastructure is subject to periodic and systematic rehabilitation and maintenance and can still be used by authorities and even by other companies. Each manhole is a potential confined space with all the constraints and problems that they usually present. A thorough and systematic analysis of the atmosphere inside the manholes of the wastewater drainage system was made to know the respective risks and hazards to all subjects exposed, throughout the East part of the city, from the gases produced and in these installations. The data collection was carried out in two different periods when the network presented minimum flows in normal operation. The flows were considered minimum after the reading of the flowmeters installed in the measurement areas indicated it.Grad Beja u Portugalu ima infrastrukturu za odvođenje otpadnih voda na daljnju obradu. Ta se infrastruktura povremeno obnavlja i održava a radove obavlja gradska uprava ili druge tvrtke. Svaki šaht je potencijalno ograničen prostor koji predstavlja razne teškoće. U istočnom dijelu grada učinjena je sustavna analiza zraka u šahtovima odvodnog sustava kako bi se utvrdili rizici i opasnosti za osobe izložene plinovima u takvim instalacijama. Podaci su prikupljani u dva navrata kad je mreža normalno radila i bila najmanje opterećena protokom. Protoci su se smatrali minimalnima kad su mjerni instrumenti za bilježenje protoka tako pokazali