Revisiting Content Availability in Distributed Online Social Networks

Online Social Networks (OSN) are among the most popular applications in today's Internet. Decentralized online social networks (DOSNs), a special class of OSNs, promise better privacy and autonomy than traditional centralized OSNs. However, ensuring availability of content when the content owner is not online remains a major challenge. In this paper, we rely on the structure of the social graphs underlying DOSN for replication. In particular, we propose that friends, who are anyhow interested in the content, are used to replicate the users content. We study the availability of such natural replication schemes via both theoretical analysis as well as simulations based on data from OSN users. We find that the availability of the content increases drastically when compared to the online time of the user, e. g., by a factor of more than 2 for 90% of the users. Thus, with these simple schemes we provide a baseline for any more complicated content replication scheme.Comment: 11pages, 12 figures; Technical report at TU Berlin, Department of Electrical Engineering and Computer Science (ISSN 1436-9915

Smart PIN: utility-based replication and delivery of multimedia content to mobile users in wireless networks

Next generation wireless networks rely on heterogeneous connectivity technologies to support various rich media services such as personal information storage, file sharing and multimedia streaming. Due to users’ mobility and dynamic characteristics of wireless networks, data availability in collaborating devices is a critical issue. In this context Smart PIN was proposed as a personal information network which focuses on performance of delivery and cost efficiency. Smart PIN uses a novel data replication scheme based on individual and overall system utility to best balance the requirements for static data and multimedia content delivery with variable device availability due to user mobility. Simulations show improved results in comparison with other general purpose data replication schemes in terms of data availability

Analysis of distributed participation and replication strategies in P2P systems.

Lin Wing Kai.Thesis (M.Phil.)--Chinese University of Hong Kong, 2005.Includes bibliographical references (leaves 90-96).Abstracts in English and Chinese.Abstract/ 摘要 --- p.iAcknowledgement --- p.ivChapter 1 --- Introduction --- p.1Chapter 1.1 --- """We are not alone""" --- p.1Chapter 1.2 --- Definition of P2P systems --- p.3Chapter 1.2.1 --- Terminologies --- p.4Chapter 1.2.2 --- Principles --- p.5Chapter 1.3 --- From sharing to replication --- p.7Chapter 1.3.1 --- Replication: why and how --- p.7Chapter 1.3.2 --- Advantages of P2P replication systems --- p.8Chapter 1.3.3 --- Typical replication approaches --- p.10Chapter 1.3.4 --- Difficulties in replication: resource allocation and replication strategy --- p.10Chapter 1.3.5 --- Why do peers cooperate? --- p.12Chapter 1.4 --- Contribution of this thesis --- p.13Chapter 1.4.1 --- Thesis organization --- p.13Chapter 2 --- Background Study --- p.15Chapter 2.1 --- Introduction --- p.15Chapter 2.2 --- Overview of P2P systems --- p.16Chapter 2.2.1 --- The original story --- p.16Chapter 2.2.2 --- Switching to decentralization --- p.16Chapter 2.2.3 --- Peer availability --- p.17Chapter 2.2.4 --- Other than file sharing --- p.18Chapter 2.3 --- Understanding replication --- p.20Chapter 2.3.1 --- File availability redefined --- p.20Chapter 2.3.2 --- Storage requirement analysis --- p.21Chapter 2.3.3 --- MTTF analysis --- p.22Chapter 2.3.4 --- Replica placement --- p.24Chapter 2.3.5 --- Other performance enhancement schemes --- p.27Chapter 2.4 --- Understanding cooperation --- p.28Chapter 2.5 --- Discussions --- p.30Chapter 3 --- Performance of erasure code replication --- p.32Chapter 3.1 --- Introduction --- p.32Chapter 3.2 --- Parameters definition --- p.33Chapter 3.2.1 --- File availability: whole file replication --- p.33Chapter 3.2.2 --- File availability: erasure code replication --- p.34Chapter 3.2.3 --- Properties of erasure code replication --- p.35Chapter 3.2.4 --- Effects of replication parameters --- p.36Chapter 3.2.5 --- Optimal value of b --- p.39Chapter 3.2.6 --- Analytical derivation --- p.40Chapter 3.3 --- Some practical considerations --- p.42Chapter 3.3.1 --- Cost of erasure code replication --- p.42Chapter 3.3.2 --- Sensitivity analysis --- p.44Chapter 3.4 --- Concluding remarks --- p.45Chapter 4 --- Distributed replication strategies --- p.48Chapter 4.1 --- Introduction --- p.48Chapter 4.2 --- The P2P replication system --- p.50Chapter 4.2.1 --- Erasure code replication --- p.50Chapter 4.2.2 --- Peers modelling --- p.51Chapter 4.2.3 --- Resource allocation problem --- p.52Chapter 4.2.4 --- Replication goal --- p.54Chapter 4.3 --- Decentralized adaptation --- p.56Chapter 4.3.1 --- Neighbour discovery and parameters exchange --- p.56Chapter 4.3.2 --- Storage resource estimation --- p.57Chapter 4.4 --- Heuristic strategies --- p.58Chapter 4.4.1 --- Random strategy --- p.58Chapter 4.4.2 --- Group partition strategy --- p.59Chapter 4.4.3 --- Highest available first (HAF) strategy --- p.61Chapter 4.5 --- Case studies --- p.65Chapter 4.5.1 --- Simulation results --- p.66Chapter 4.6 --- Concluding remarks --- p.69Chapter 5 --- Before cooperation: why do peers join? --- p.72Chapter 5.1 --- Introduction --- p.72Chapter 5.2 --- Information sharing club (ISC) model --- p.73Chapter 5.3 --- An example: music information sharing club --- p.75Chapter 5.4 --- Necessary condition for ISC to grow --- p.76Chapter 5.4.1 --- Music information sharing club example with simple requests --- p.78Chapter 5.5 --- Concluding remarks --- p.81Chapter 6 --- Conclusion --- p.83Chapter A --- Proof in this thesis --- p.86Bibliography --- p.9