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**1 - 9**of**9**### Converging an Overlay Network to a Gradient Topology

"... Abstract — In this paper, we investigate the topology conver-gence problem for the gossip-based Gradient overlay network. In an overlay network where each node has a local utility value, a Gradient overlay network is characterized by the properties that each node has a set of neighbors with the same ..."

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Abstract — In this paper, we investigate the topology conver-gence problem for the gossip-based Gradient overlay network. In an overlay network where each node has a local utility value, a Gradient overlay network is characterized by the properties that each node has a set of neighbors with the same utility value (a similar view) and a set of neighbors containing higher utility values (gradient neighbor set), such that paths of increasing utilities emerge in the network topology. The Gradient overlay network is built using gossiping and a preference function that samples from nodes using a uniform random peer sampling service. We analyze it using tools from matrix analysis, and we prove both the necessary and sufficient conditions for convergence to a complete gradient structure, as well as estimating the convergence time and providing bounds on worst-case convergence time. Finally, we show in simulations the potential of the Gradient overlay, by building a more efficient live-streaming peer-to-peer (P2P) system than one built using uniform random peer sampling.

### Converging an Overlay Network to a Gradient Topology

"... Abstract — In this paper, we investigate the topology conver-gence problem for the gossip-based Gradient overlay network. In an overlay network where each node has a local utility value, a Gradient overlay network is characterized by the properties that each node has a set of neighbors containing hi ..."

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Abstract — In this paper, we investigate the topology conver-gence problem for the gossip-based Gradient overlay network. In an overlay network where each node has a local utility value, a Gradient overlay network is characterized by the properties that each node has a set of neighbors containing higher utility values, such that paths of increasing utilities emerge in the network topology. The Gradient overlay network is built using gossiping and a preference function that samples from nodes using a uniform random peer sampling service. We analyze it using tools from matrix analysis, and we prove both the necessary and sufficient conditions for convergence to a complete gradient structure, as well as estimating the convergence time. Finally, we show in simulations the potential of the Gradient overlay, by building a more efficient live-streaming peer-to-peer (P2P) system than one built using uniform random peer sampling.

### Converging an Overlay Network to a Gradient Topology

"... Abstract — In this paper, we investigate the topology conver-gence problem for the gossip-based Gradient overlay network. In an overlay network where each node has a local utility value, a Gradient overlay network is characterized by the properties that each node has a set of neighbors containing hi ..."

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Abstract — In this paper, we investigate the topology conver-gence problem for the gossip-based Gradient overlay network. In an overlay network where each node has a local utility value, a Gradient overlay network is characterized by the properties that each node has a set of neighbors containing higher utility values, such that paths of increasing utilities emerge in the network topology. The Gradient overlay network is built using gossiping and a preference function that samples from nodes using a uniform random peer sampling service. We analyze it using tools from matrix analysis, and we prove both the necessary and sufficient conditions for convergence to a complete gradient structure, as well as estimating the convergence time. Finally, we show in simulations the potential of the Gradient overlay, by building a more efficient live-streaming peer-to-peer (P2P) system than one built using uniform random peer sampling.

### Converging an Overlay Network to a Gradient Topology

"... Abstract — In this paper, we investigate the topology conver-gence problem for the gossip-based Gradient overlay network. In an overlay network where each node has a local utility value, a Gradient overlay network is characterized by the properties that each node has a set of neighbors containing hi ..."

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Abstract — In this paper, we investigate the topology conver-gence problem for the gossip-based Gradient overlay network. In an overlay network where each node has a local utility value, a Gradient overlay network is characterized by the properties that each node has a set of neighbors containing higher utility values, such that paths of increasing utilities emerge in the network topology. The Gradient overlay network is built using gossiping and a preference function that samples from nodes using a uniform random peer sampling service. We analyze it using tools from matrix analysis, and we prove both the necessary and sufficient conditions for convergence to a complete gradient structure, as well as estimating the convergence time. Finally, we show in simulations the potential of the Gradient overlay, by building a more efficient live-streaming peer-to-peer (P2P) system than one built using uniform random peer sampling.

### Load Balancing in a Distributed Storage System for Big and Small Data

"... Abstract Distributed storage services form the backbone of modern large-scale applications and data processing solutions. In this integral role they have to provide a scalable, reliable and performant service. One of the major challenges any distributed storage system has to address is skew in the ..."

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Abstract Distributed storage services form the backbone of modern large-scale applications and data processing solutions. In this integral role they have to provide a scalable, reliable and performant service. One of the major challenges any distributed storage system has to address is skew in the data load, which can either be in the distribution of data items or data access over the nodes in the system. One widespread approach to deal with skewed load is data assignment based on uniform consistent hashing. However, there is an opposing desire to optimise and exploit data-locality. That is to say, it is advantageous to collocate items that are typically accessed together. Often this locality property can be achieved by storing keys in an ordered fashion and using application level knowledge to construct keys in such a way that items accessed together will end up very close together in the key space. It can easily be seen, however, that this behaviour exacerbates the load skew issue. A different approach to load balancing is partitioning the data into small subsets which can be relocated independently. These subsets may be known as partitions, tablets or virtual nodes, for example. In this thesis we present the design of CaracalDB, a distributed keyvalue store which provides automatic load-balancing and data-locality, as well as fast re-replication after node failures, while remaining flexible enough to support different consistency levels to choose from. We also evaluate an early prototype of the system, and show that the approach is viable.

### Final report: Dynamic peer-to-peer game networks using WebRTC

, 2013

"... This document is the final report on the Bachelor Project conducted by Jasper Abbink, Karens Grigorjancs and Joost Verdoorn on Dynamic peer-to-peer game networks using WebRTC. In this report we detail our findings on the recently developed WebRTC technology. WebRTC enables the creation of web applic ..."

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This document is the final report on the Bachelor Project conducted by Jasper Abbink, Karens Grigorjancs and Joost Verdoorn on Dynamic peer-to-peer game networks using WebRTC. In this report we detail our findings on the recently developed WebRTC technology. WebRTC enables the creation of web applica-tions built around peer-to-peer technologies by providing the means to directly connect one browser to another. With this project we aimed to facilitate web de-velopers by developing a software library that is a drop-in solution for large-scale peer-to-peer networks. We investigated the scalability of WebRTC networks and attempted to seek the edges of the technology. We evaluated a number of ways by which a browser-based peer-to-peer networks can be deployed, and imple-mented the ones that best suited our needs. To demonstrate our library we created a small massively-multiplayer arcade game as an entertaining way to display WebRTC's capabilities.

### DOI 10.1007/s12083-009-0062-6 Decentralising a service-oriented architecture

, 2009

"... © The Author(s) 2009. This article is published with open access at Springerlink.com Abstract Service-oriented computing is becoming an increasingly popular paradigm for modelling and building distributed systems in open and heterogeneous environments. However, proposed service-oriented architecture ..."

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© The Author(s) 2009. This article is published with open access at Springerlink.com Abstract Service-oriented computing is becoming an increasingly popular paradigm for modelling and building distributed systems in open and heterogeneous environments. However, proposed service-oriented architectures are typically based on centralised components, such as service registries or service brokers, that introduce reliability, management, and performance issues. This paper describes an approach to fully decentralise a service-oriented architecture using a selforganising peer-to-peer network maintained by service providers and consumers. The design is based on a gradient peer-to-peer topology, which allows the system to replicate a service registry using a limited number of the most stable and best performing peers. The paper evaluates the proposed approach through extensive simulation experiments and shows that the decentralised registry and the underlying peer-to-peer infrastructure scale to a large number of peers and can successfully manage high peer churn rates.

### Converging an Overlay Network to a Gradient Topology

"... Abstract — In this paper, we investigate the topology conver-gence problem for the gossip-based Gradient overlay network. In an overlay network where each node has a local utility value, a Gradient overlay network is characterized by the properties that each node has a set of neighbors with the same ..."

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Abstract — In this paper, we investigate the topology conver-gence problem for the gossip-based Gradient overlay network. In an overlay network where each node has a local utility value, a Gradient overlay network is characterized by the properties that each node has a set of neighbors with the same utility value (a similar view) and a set of neighbors containing higher utility values (gradient neighbor set), such that paths of increasing utilities emerge in the network topology. The Gradient overlay network is built using gossiping and a preference function that samples from nodes using a uniform random peer sampling service. We analyze it using tools from matrix analysis, and we prove both the necessary and sufficient conditions for convergence to a complete gradient structure, as well as estimating the convergence time and providing bounds on worst-case convergence time. Finally, we show in simulations the potential of the Gradient overlay, by building a more efficient live-streaming peer-to-peer (P2P) system than one built using uniform random peer sampling.

### Evaluating P2P Live Streaming Systems: the CNG Case∗

"... Many peer-to-peer (P2P) systems have been proposed for the provision of scalable live video streaming services over the Internet. While the literature contains surveys of the architectures of these systems, there is a lack of work on methodologies for their evaluation. We identify the main issues in ..."

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Many peer-to-peer (P2P) systems have been proposed for the provision of scalable live video streaming services over the Internet. While the literature contains surveys of the architectures of these systems, there is a lack of work on methodologies for their evaluation. We identify the main issues in the evaluation of P2P live streaming systems and use the Community Network Game (CNG) project as an ex-ample to illustrate them. The evaluation of the P2P sys-tem consists of two phases: a laboratory one using the ns-2 network simulator and an online field test with Massively Multiplayer Online Games (MMOG) players. 1.