Robustness of BitTorrent-like VoD protocols

Besides server supported solutions for Video-on-demand, approaches based on distributed systems such as BitTorrent are being used due to their efficiency and high scalability. There are several protocol variants proposed in the literature, which are mainly concerned with providing mechanisms for piece selection and peer selection. In this paper, using the concept of Design Space Analysis, we give comparisons of the performances of several BitTorrent-like Video-on-demand protocols under the assumption that other protocol variants may also enter the system

Closeness centrality reconstruction of tree graphs

This paper deals with a problem which belongs to the general question: how to reconstruct a graph from limited amount of information. As given information, we use the closeness centrality, which assigns a non-negative number to each node of the graph in question: the reciprocal of the sum of the length of the shortest paths between the node and all other nodes in the graph. Here we consider the case when the original graph is a tree and it is also known which nodes are the leaves. Based on some theoretical results, three algorithms are proposed. The first one aims at finding a non-exact solution G(P) in short time; the second one is a metaheuristic with some variants, they are intended to give further improvement on G(P); and the third one is designed for giving accurate results. Detailed explanations of these algorithms are given, together with numerical experiments to demonstrate their efficiency

Towards the Coevolution of Incentives in BitTorrent

BitTorrent is a peer-to-peer file sharing system that is open to variant behavior at the peer level through modification of the client software. A number of different variants have been released and proposed. Some are successful and become widely used whereas others remain in a small minority or are not used at all. In previous work we explored the performance of a large set of client variants over a number of dimensions by applying Axelrod’s round-robin pairwise tournament approach. However, this approach does not capture the dynamics of client change over time within pairwise tournaments. In this work we extend the tournament approach to include a limited evolutionary step, within the pairwise tournaments, in which peers copy their opponents strategy (client variant) if it outperforms their own and also spontaneously change to the opponents strategy with a low mutation probability. We apply a number of different evolutionary algorithms and compare them with the previous non-evolutionary tournament results. We find that in most cases cooperative (sharing) strategies outperformed free riding strategies. These results are comparable to those previously obtained using the round-robin approach without evolution. We selected this limited form of evolution as a step towards understanding the full coevolutionary dynamics that would result from evolution between a large space of client variants in a shared population rather than just pairs of variants. We conclude with a discussion on how such future work might proceed. © 2015, Budapest Tech Polytechnical Institution. All rights reserved

On maximum throughput in BitTorrent

The resource allocation problem reguesting maximum through- Put in BitTorrent networks is investigated. It is known from the iterature that the total throughput of BitTorrent is far from the the- oretical maximum. However, direct implementation of the uncon- strained maximum flow model into BitTorrent is not desirable, due to the necessity of further social considerations. This paper aims to produce more realistic upper bound for maximum throughput in BitTorrent networks by suggesting new model variants to move the maximum flow model closer to the rules of a typical BitTorrent community. Numerical experiments are done on those modified models, introducing lower bounds and balancing constraints on the amount of downloading and uploading, to verify their impact. Additionally, computational results are presented for comparing the network linear program model and the standard algebraic model of the maximum flow problem in AMPL