This thesis details the integration of a common collaboration technique, desktop sharing, into a virtual world environment. Previous literature shows no intersection between these fields. This thesis will illustrate that existing collaboration technology can be integrated into virtual worlds with a minimal amount of effort. Outlined in this thesis are the developmental and procedural challenges encountered in demonstrating seamless desktop sharing in a virtual environment and a stress test of the integrated system revealing that the inclusion of desktop sharing resulted in minor performance loss. The Problem Current virtual world technology has limited capability for collaboration because of a lack of collaboration tools. This thesis proposes that it is feasible to take a common collaboration tool such as desktop sharing and introduce it into a virtual world. / Department of Computer Science

With network enabled consumer devices becoming increasingly popular, the number of connected devices and available services is growing considerably - with the number of connected devices es- timated to surpass 15 billion devices by 2015. In this increasingly large and dynamic environment it is important that users have a comprehensive, yet efficient, mechanism to discover services. Many existing wide-area service discovery mechanisms are centralised and do not scale to large numbers of users. Additionally, centralised services suffer from issues such as a single point of failure, high maintenance costs, and difficulty of management. As such, this Thesis seeks a Peer to Peer (P2P) approach. Distributed Hash Tables (DHTs) are well known for their high scalability, financially low barrier of entry, and ability to self manage. They can be used to provide not just a platform on which peers can offer and consume services, but also as a means for users to discover such services. Traditionally DHTs provide a distributed key-value store, with no search functionality. In recent years many P2P systems have been proposed providing support for a sub-set of complex query types, such as keyword search, range queries, and semantic search. This Thesis presents a novel algorithm for performing any type of complex query, from keyword search, to complex regular expressions, to full-text search, over any structured P2P overlay. This is achieved by efficiently broadcasting the search query, allowing each peer to process the query locally, and then efficiently routing responses back to the originating peer. Through experimentation, this technique is shown to be successful when the network is stable, however performance degrades under high levels of network churn. To address the issue of network churn, this Thesis proposes a number of enhancements which can be made to existing P2P overlays in order to improve the performance of both the existing DHT and the proposed algorithm. Through two case studies these enhancements are shown to improve not only the performance of the proposed algorithm under churn, but also the performance of traditional lookup operations in these networks.

Jia, Lu. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (p. 76-80). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.iv / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Background Study --- p.7 / Chapter 3 --- Analysis of P2P Tracker Designs --- p.11 / Chapter 1 --- Tracker design in P2P systems --- p.11 / Chapter 1.1 --- A taxonomy of tracker designs --- p.11 / Chapter 1.2 --- Design considerations --- p.14 / Chapter 2 --- A reliability model for DHT-based tracker design --- p.15 / Chapter 2.1 --- DHT basics --- p.15 / Chapter 2.2 --- Model preliminaries and assumptions --- p.16 / Chapter 2.3 --- Model description --- p.18 / Chapter 3 --- Reliability analysis --- p.25 / Chapter 3.1 --- Related parameters --- p.25 / Chapter 3.2 --- Simulation setup --- p.27 / Chapter 3.3 --- Results --- p.30 / Chapter 3.4 --- Observations from modeling work --- p.35 / Chapter 3.5 --- Methods of DHT stabilization --- p.37 / Chapter 4 --- A Black-Box Study of Xunlei --- p.44 / Chapter 1 --- An Overview of Xunlei and its key components --- p.44 / Chapter 1.1 --- An overview --- p.44 / Chapter 1.2 --- Key components --- p.46 / Chapter 2 --- Participating into other swarms: Xunlei´ةs multi-protocol downloading strategy --- p.47 / Chapter 2.1 --- BitTorrent and eMule basics --- p.47 / Chapter 2.2 --- BitTorrent and eMule in Xunlei --- p.48 / Chapter 2.3 --- Multi-protocol downloading --- p.52 / Chapter 3 --- Xunlei servers --- p.54 / Chapter 4 --- Understanding Xunlei!s private protocol --- p.56 / Chapter 4.1 --- Exchanging peer lists --- p.56 / Chapter 4.2 --- Exchanging file data --- p.58 / Chapter 4.3 --- Error control and congestion control --- p.62 / Chapter 5 --- Further discussions --- p.65 / Chapter 5.1 --- Proximity of content --- p.65 / Chapter 5.2 --- Active swarm peers --- p.66 / Chapter 5.3 --- UDP-based data transmission --- p.69 / Chapter 5 --- Conclusion --- p.74 / Bibliography --- p.76

The explosive growth in on-demand access of video across all forms of delivery (Internet, traditional cable, IPTV, wireless) has renewed the interest in scalable delivery methods. Approaches using Content Delivery Networks (CDNs), Peer-to-Peer (P2P) approaches, and their combinations have been proposed as viable options to ease the load on servers and network links. However, there has been little focus on how to take advantage of user viewing patterns to understand their impact on existing mechanisms and to design new solutions that improve the streaming service quality. In this dissertation, we leverage on the observation that users watch only a small portion of videos to understand the limits of existing designs and to optimize two scalable approaches -- the content placement and P2P Video-on-Demand (VoD) streaming. Then, we present our novel scalable system called Joint-Family which enables adaptive bitrate streaming (ABR) in P2P VoD, supporting user viewing patterns. We first provide evidence of such user viewing behavior from data collected from a nationally deployed VoD service. In contrast to using a simplistic popularity-based placement and traditionally proposed caching strategies (such as CDNs), we use a Mixed Integer Programming formulation to model the placement problem and employ an innovative approach that scales well. We have performed detailed simulations using actual traces of user viewing sessions (including stream control operations such as pause, fast-forward, and rewind). Our results show that the use of segment-based placement strategy yields substantial savings in both disk storage requirements at origin servers/VHOs as well as network bandwidth use. For example, compared to a simple caching scheme using full videos, our MIP-based placement using segments can achieve up to 71% reduction in peak link bandwidth usage. Secondly, we note that the policies adopted in existing P2P VoD systems have not taken user viewing behavior -- that users abandon videos -- into account. We show that abandonment can result in increased interruptions and wasted resources. As a result, we reconsider the set of policies to use in the presence of abandonment. Our goal is to balance the conflicting needs of delivering videos without interruptions while minimizing wastage. We find that an Earliest-First chunk selection policy in conjunction with the Earliest-Deadline peer selection policy allows us to achieve high download rates. We take advantage of abandonment by converting peers to "partial seeds"; this increases capacity. We minimize wastage by using a playback lookahead window. We use analysis and simulation experiments using real-world traces to show the effectiveness of our approach. Finally, we propose Joint-Family, a protocol that combines P2P and adaptive bitrate (ABR) streaming for VoD. While P2P for VoD and ABR have been proposed previously, they have not been studied together because they attempt to tackle problems with seemingly orthogonal goals. We motivate our approach through analysis that overcomes a misconception resulting from prior analytical work, and show that the popularity of a P2P swarm and seed staying time has a significant bearing on the achievable per-receiver download rate. Specifically, our analysis shows that popularity affects swarm efficiency when seeds stay "long enough". We also show that ABR in a P2P setting helps viewers achieve higher playback rates and/or fewer interruptions. We develop the Joint-Family protocol based on the observations from our analysis. Peers in Joint-Family simultaneously participate in multiple swarms to exchange chunks of different bitrates. We adopt chunk, bitrate, and peer selection policies that minimize occurrence of interruptions while delivering high quality video and improving the efficiency of the system. Using traces from a large-scale commercial VoD service, we compare Joint-Family with existing approaches for P2P VoD and show that viewers in Joint-Family enjoy higher playback rates with minimal interruption, irrespective of video popularity.

Lin, Minghong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (p. 49-51). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.v / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- A Stochastic Framework --- p.5 / Chapter 2.1 --- Model Description --- p.5 / Chapter 2.2 --- Altruistic File Sharing System with Download Con- straint --- p.7 / Chapter 2.2.1 --- Model Formulation --- p.8 / Chapter 2.2.2 --- Steady State Analysis --- p.9 / Chapter 2.3 --- Altruistic File Sharing System with Download and Upload Constraints --- p.14 / Chapter 2.3.1 --- Model Formulation --- p.14 / Chapter 2.3.2 --- Steady State Analysis --- p.15 / Chapter 2.4 --- Incentive File Sharing via Coordinated Matching --- p.18 / Chapter 2.4.1 --- Without Incentive Mechanism --- p.18 / Chapter 2.4.2 --- With Incentive Mechanism --- p.19 / Chapter 2.5 --- Simulation --- p.23 / Chapter 3 --- An ISP-friendly Protocol --- p.28 / Chapter 3.1 --- Simple Mathematical Models --- p.28 / Chapter 3.1.1 --- Assumptions --- p.29 / Chapter 3.1.2 --- Homogeneous Case Analysis --- p.30 / Chapter 3.1.3 --- Heterogeneous Case Analysis --- p.31 / Chapter 3.1.4 --- Flash Crowd Analysis --- p.32 / Chapter 3.2 --- An ISP-friendly BitTorrent Protocol --- p.33 / Chapter 3.3 --- Performance Evaluation & Measurements --- p.36 / Chapter 3.3.1 --- Choice of the BitTorrent Client --- p.37 / Chapter 3.3.2 --- Experimental Setup --- p.37 / Chapter 3.3.3 --- Regular Peer Arrival --- p.38 / Chapter 3.3.4 --- Flash Crowd --- p.41 / Chapter 3.4 --- Black Hole Security Attack --- p.42 / Chapter 4 --- Related Work --- p.46 / Chapter 5 --- Conclusion --- p.48 / Bibliography --- p.49 / Appendix --- p.52

Implementing Shamir's secret sharing scheme using floating point arithmetic would provide a faster and more efficient secret sharing scheme due to the speed in which GPUs perform floating point arithmetic. However, with the loss of a finite field, properties of a perfect secret sharing scheme are not immediately attainable. The goal is to analyze the plausibility of Shamir's secret sharing scheme using floating point arithmetic achieving the properties of a perfect secret sharing scheme and propose improvements to attain these properties. Experiments indicate that property 2 of a perfect secret sharing scheme, "Any k-1 or fewer participants obtain no information regarding the shared secret", is compromised when Shamir's secret sharing scheme is implemented with floating point arithmetic. These experimental results also provide information regarding possible solutions and adjustments. One of which being, selecting randomly generated points from a smaller interval in one of the proposed schemes of this thesis. Further experimental results indicate improvement using the scheme outlined. Possible attacks are run to test the desirable properties of the different schemes and reinforce the improvements observed in prior experiments. / by Timothy Finemore. / Thesis (M.S.)--Florida Atlantic University, 2012. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2012. Mode of access: World Wide Web.

Peer-to-Peer (P2P) overlays were initially proposed for use with wired networks. However, the very rapid proliferation of wireless communication technology has prompted a need for adoption of P2P systems in mobile networks too. There are many common characteristics between P2P overlay networks and Mobile Ad-hoc Networks (MANET). Self-organization, decentralization, a dynamic nature and changing topology are the most commonly shared features. Furthermore, when used together, the two approaches complement each other. P2P overlays provide data storage/retrieval functionality and MANET provides wireless connectivity between clients without depending on any pre-existing infrastructure. P2P overlay networks can be deployed over MANET to address content discovery issues. However, previous research has shown that deploying P2P systems straight over MANET does not exhibit satisfactory performance. Bandwidth limitation, limited resources and node mobility are some of the key constraints. This thesis proposes a novel approach, OneHopOverlay4MANET, to exploit the synergies between MANET and P2P overlays through cross-layering. It combines Distributed Hash Table (DHT) based structured P2P overlays with MANET underlay routing protocols to achieve one logical hop between any pair of overlay nodes. OneHopOverlay4MANET constructs a cross-layer channel to permit direct exchange of routing information between the Application layer, where the overlay operates, and the MANET underlay layer. Consequently, underlay routing information can be shared and used by the overlay. Thus, OneHopOverlay4MANET reduces the typical management traffic when deploying traditional P2P systems over MANET. Moreover, as a result of building one hop overlay, OneHopOverlay4MANET can eliminate the mismatching issue between overlay and underlay and hence resolve key lookups in a short time, enhancing the performance of the overlay. v In this thesis, we present OneHopOverlay4MANET and evaluate its performance when combined with different underlay routing protocols. OneHopOverlay4MANET has been combined with two proactive underlays (OLSR and BATMAN) and with three reactive underlay routing protocols (DSR, AODV and DYMO). In addition, the performance of the proposed system over OLSR has been compared to two recent structured P2P over MANET systems (MA-SP2P and E-SP2P) that adopted OLSR as the routing protocol. The results show that better performance can be achieved using OneHopOverlay4MANET.

The aim of this paper is to investigate how the view on copyright emerges in the media debate, and the overall research question is what possible explanations there might be for the view being different depending on whom the writer is and whom s/he represents. The theoretical framework is Fairclough's critical discourse analysis and the method used is the analytic model in three stages that he presents in his book Language and Power (2001). The empirical material was selected through an initial search in Media Retriever, followed by a manual se-lection process, which resulted in a final selection of eight articles, all published in Swedish daily newspapers between the years 2006 and 2014. In the analysis, two main discourses were identified – the producer discourse and the consumer discourse – in which all the texts could be placed. The producer discourse puts the interests of the author first, and holds the view that copyright law must be strong to protect the authors' rights. The consumer discourse on the other hand puts the interest of the consumer first, and their view is that the public has the right to access the world's collect-ed knowledge and culture. This paper also examines the members' resources that authors bring to the texts in the form of common sense, and also in the form of a motive for entering in the debate. Furthermore, this paper also looks at the fact that power relations between the participants in the texts are complicated as they form a com-plex web of formal and informal power relations. The conclusion is that the main explanation for the different ways of viewing copyright is the two afore-mentioned discourses, and that the members' resources the authors bring to the texts are very ideological. The ideological arguments and the complex power relations result in very rigid positions in the debate. This is a two years master's thesis in Archive, Library and Museum studies.

A study is done on the protection of sound recordings in the decentralized peer-to-peer (DP2P) file sharing in the United States, the United Kingdom and South Africa. This study reveals that because sound recordings have unique features different from other copyright works, the illegal sharing of sound recordings can ordinarily be filtered, identified, and detected by the Internet service providers (ISPs) before granting access to users and without infringing the users‟ right to privacy. However, the ISPs have failed in this regard, hence, they are strictly held liable under the contributory, vicarious and inducing infringements notwithstanding the statutory law which prohibits ISPs from monitoring, and intercepting their networks. In fact and law, the terms filtering, identifying and detecting on the one hand and monitoring and intercepting on the other hand are different in relation to sound recordings and as such ISPs are not prohibited from filtering, identifying and detecting illegal sound recordings on their networks, thus, ISPs are not protected under the limitation law as it is generally believed. However, several recommendations are made for reform, inter alia: a review of the limitation law to include the terms filtering, identifying and detecting in pursuance of the terms monitoring, and intercepting, if the intention of the legislators was meant to include the latter terms; protection of access right in digital sound recordings, protection of the neighbouring rights of ISPs in the digital world, imposing levies on all recording equipment, the insurability of sound recordings and ISPs‟ signals, and bandwidth. / Mercentile Law / LL. M. (Mercantile Law)

A study is done on the protection of sound recordings in the decentralized peer-to-peer (DP2P) file sharing in the United States, the United Kingdom and South Africa. This study reveals that because sound recordings have unique features different from other copyright works, the illegal sharing of sound recordings can ordinarily be filtered, identified, and detected by the Internet service providers (ISPs) before granting access to users and without infringing the users‟ right to privacy. However, the ISPs have failed in this regard, hence, they are strictly held liable under the contributory, vicarious and inducing infringements notwithstanding the statutory law which prohibits ISPs from monitoring, and intercepting their networks. In fact and law, the terms filtering, identifying and detecting on the one hand and monitoring and intercepting on the other hand are different in relation to sound recordings and as such ISPs are not prohibited from filtering, identifying and detecting illegal sound recordings on their networks, thus, ISPs are not protected under the limitation law as it is generally believed. However, several recommendations are made for reform, inter alia: a review of the limitation law to include the terms filtering, identifying and detecting in pursuance of the terms monitoring, and intercepting, if the intention of the legislators was meant to include the latter terms; protection of access right in digital sound recordings, protection of the neighbouring rights of ISPs in the digital world, imposing levies on all recording equipment, the insurability of sound recordings and ISPs‟ signals, and bandwidth. / Mercentile Law / LL. M. (Mercantile Law)