Made available in DSpace on 2016-12-23T14:33:45Z (GMT). No. of bitstreams: 1 Dissertacao de Renan Manola.pdf: 2122768 bytes, checksum: 34bb5f10fcba2c8572886719aa4c1f74 (MD5) Previous issue date: 2011-08-04 / Peer-to-Peer Video on Demand Systems have well stabilished its importance in recent years. Such consolidation is due to the high gains that may be archieved in terms savings in transmission bandwidth of the servers. In this work, we evaluate how this technology can enhance the gains for the transmission of continuous media over the Internet. To achieve this goal, the methodology relies on a packet-level simulation that has the ability to allow capturing different variables that regard the dynamics of the Internet, such as: full simulation of the TCP/IP stack, considerations on network topology and insertion of background traffic. In this simulation was implemented a video streaming P2P VoD algorithm and an algorithm that uses pre-fetching. Result analisys point out to a potential economy of the content server s upload bandwidth of up to 43% in a less idealized scenario than the results obtained on the base proposal that has archieved an economy of 73%. In terms of user s perceived video quality, this work indicates that the user s experience can be greatly degraded when using the UDP with background traffic, even with the economy of the server remaining constant. Still on the user s video quality perception, it was noted that, although the use of pre-fetching was proved beneficial to them, the key factor in best quality perceived was the choice of a proper transport / Sistemas Par-a-Par de Video Sob Demanda consolidaram sua importância nos últimos anos. Tal consolidação é decorrente dos elevados ganhos que se pode ter em termos de economia na banda de transmissão dos servidores. Neste trabalho, avalia-se como esta tecnologia pode potencializar os ganhos de transmissão de mídia contínua na Internet. Para atingir este objetivo, a metodologia adotada apoia-se em um ambiente de simulação a nível de pacotes que possui características que permitem capturar diferentes variáveis referentes a dinâmica da Internet, tais como: simulação completa da pilha TCP/IP, considerações sobre topologia de rede e inserção de tráfego de fundo. Na simulação foi implementado um algoritmo de difusão de vídeo P2P VoD e um algoritmo de pré-busca. As análises dos resultados apontam para uma potencial economia de upload no servidor de conteúdo de 43% em um cenário menos idealizado do que a proposta de base que atingiu 73%. Em termos da percepção da qualidade de vídeo dos clientes, o presente trabalho indica que sua experiência pode ser degradada de forma considerável usando UDP quando existe o tráfego de fundo, mesmo com a economia do servidor se mantendo constante. Ainda na percepção dos clientes, percebeu-se também que, embora o uso da pré-busca seja benéfico aos mesmos, o grande fator diferencial na melhor qualidade percebida foi a escolha da camada de transporte apropriada

As the amount of valuable data that the average person owns increases, there is a growing need for personal low cost backup services. A variety of methods have been developed to fulfill this need, from cloud based backup services to cooperative methods where users share spare resources to store each other’s data, either using a peer-to-peer (P2P) network to store data among a large number of diverse peers, or a friend-to-friend (F2F) network to store data among a smaller number of trusted friends. There are several advantages to each method, but they all have issues that can make them unsuitable for this task. The purpose of this thesis is to explore the possibility of avoiding these issues by creating a hybrid system that stores files using a combination of cloud storage and trust aware P2P and F2F networks. This should also give the user greater control over the distribution of files and make it more resilient towards malicious peers. A simple file storage system was designed that uses a combined P2P and F2F network together with a reputation system for determining how trustworthy a peer is based on its past behavior, as well as having the option of falling back on cloud storage. The user decides for each file how much data shall be stored using normal peers, friend peers, and cloud storage, and any requirements that the peers used must fulfill. A partial implementation of the system was created as part of a simulator used to evaluate how well the combined P2P and F2F networks and reputation system behaves in various circumstances, and using different distribution policies. While it is difficult to compare the performance of this system to that of other backup and file storage systems without more thorough testing, the results obtained show that it is in fact possible to construct a trustaware hybrid system, that it should perform better than a pure P2P or F2F system, and that it should perform well even if a majority of all peers were to act maliciously.

Is a regulating policy concerning peer-to-peer applications required so that companies and institutions can better manage the security issues of internal peer-to-peer applications? There is high security and privacy risks involved when using p2p applications like KaZaA, Bearshare, Audiogalaxy and ICQ. With the high speed networks of today it is very important to really know what is going on in your network and which applications is doing what and with whom. If not, there are high possibilities that your system will be used for more or less malicious purposes. Therefore it is interesting to find out if p2p applications have found their way behind company walls. A policy can prevent the issues discussed either by banning employees from using p2p applications or by regulate the use of these applications in a very detailed manner. The implementation of a policy makes the usage controlled and easily supervised by the company security staff. Implementing a policy that regulates the use of p2p applications can prevent possible attacks on the company/organisation network.

Le besoin des applications de streaming multimédia en temps réel sur Internet ne cesse d’accroître. Dans ce contexte, les réseaux Pair-à-Pair (P2P) jouent un rôle prépondérant afin d’assurer une transmission robuste et extensible (scalable) de contenu multimédia à grand-échelle. Cependant, le déploiement des applications de streaming multimédia à travers les réseaux P2P présente plusieurs verrous. En effet, les applications de streaming vidéo nécessitent une garantie de performances temps réel en termes de : délai minimal de bout-en-bout, faible taux de perte de paquets et garantie de la bande passante. Par ailleurs, un réseau P2P est composé d’un ensemble de terminaux interconnectés à travers des réseaux hétérogènes, n’ayant pas forcément les mêmes caractéristiques requises afin d’offrir la même qualité vidéo aux clients finaux.Dans cette thèse, nous analysons différents problèmes liés au streaming en-direct (Live) ou à la demande (VoD) de la vidéo sur les réseaux P2P, et nous proposons un ensemble de mécanismes pour y remédier. / There is an increasing demand for efficient deployment of real-time multimedia streaming applications over Internet. In this context, Peer-to-Peer (P2P) networks are playing an important role for supporting robust and scalable transmission of multimedia content to large-scale and massive receivers. P2P networks consist of different heterogeneous networks and devices, which may not have symmetric characteristics to offer the same video quality to end clients. The deployment of streaming applications such as live and on-demand over P2P networks is challenging. Indeed, video streaming applications require real-time performance guarantee in terms of low end-to-end delay, low packet loss and guaranteed available bandwidth. Moreover, P2P video streaming also experiences the problems of long start-time and churn-induced instability. The situation leads to affect the viewing experience of the users in P2P networks.The aim of this thesis is to analyze these issues and to propose quality-aware mechanisms for both live and on-demand streaming over P2P networks. Our contributions in this dissertation are threefold. First, we propose a small world overlay organization mechanism allowing efficient organization of peers to reduce the end-to-end delay for live streaming applications. Second, we propose a mechanism for cooperative prefetching with differentiated chunks scheduling suitable for P2P video-on-demand (VoD) to efficiently handle seek operations while reducing the response latency and increasing the hit ratio. Finally, we present a smoothing mechanism for layered streaming in P2P networks. The mechanism aims to reduce the number of layer changes under varying network conditions while at the same time achieving a high delivery ratio.

Context. Online piracy is widespread, controversial and poorly understood social phenomena that affects content creators, owners, and consumers. Online piracy, born from recent, rapid ITC changes, raises legal, ethical, and business challenges. Content owners, authors and content consumers should benefit from better understanding of online piracy. Improved, better adapted to marketplace and ITC changes content distribution models should benefit content owners and audiences.Objectives. Investigate online piracy effect on pirated product sales. Improve understanding of online piracy behaviors and process scale.Methods. This observational study investigated movie-sharing effect on U.S. box office. Movie sharing was observed over BitTorrent network, the most popular peer-to-peer file-sharing network. Relationship between piracy and sales was analyzed using linear regression model.Results. File sharing was found to have a slightly positive correlation with U.S. box office sales during first few weeks after film release, and no effect afterwards. Most of newly released movies are shared over BitTorrent network. File sharing is a global, massive phenomenon.Conclusions. I conclude that online movie file sharing has no negative correlation on U.S. box office. Slightly positive movie sharing correlation to box office sales could have occurred because sharing rather informs, than substitutes cinema going.

Existing VoD solutions often rely on unicast to distribute content, which leads to a higher load on the VoD server as more nodes become interested in the content. In such case, P2P is an alternative way of distributing content since it makes better use of available resources in the network. In this report, several P2P structures are evaluated from an operators point of view. We believe BitTorrent is the most adequate protocol for a P2P solution in IPTV environments. Two BitTorrent clients have been implemented on an IP-STB as proof of concept to find out whether P2P is suited for IPTV environments. Several tests were conducted to evaluate the performance of both clients and to see if they were able to reach a sufficient throughput on the IP-STB. Based upon the tests and the overall impressions, we are convinced that this particular P2P protocol is well suited for IPTV environments. Hopefully, a client developed from scratch for the IP-STB will offer even greater characteristics. Further, we have studied how to share recorded content among IP-STBs. Such a design would probably have many similarities to BitTorrent since a central node needs to keep track of content; the IP-STBs take care of the rest. The report also brings up whether BitTorrent is suitable for streaming. We believe that the necessary changes required to obtain such functionality will disrupt the strengths of BitTorrent. Some alternative solutions are presented where BitTorrent has been extended with additional modules, such as a server.

中小企業是全球經濟成長的主要動能，且有望成為金融科技潛在得利者，而融資更在金融科技應用中扮演重要的角色，結合科技的應用，可以更進一步以非結構化資料建立信用評分模型以評估信用風險，不僅能更加瞭解顧客、達到精準行銷，使風險的估計更為準確。結合金融科技的新興融資方式，P2P借貸將為中小企業資金融通帶來了新的方向，消費信貸商品與傳統股債市相關性較低，提供小額投資人一多角化的新形態投資標的。 / Small and Medium Enterprises (SMEs) are the main drivers of global economic growth and are expected to become potential beneficiaries of financial technology. Besides, financing also plays an important role in the application of financial technology. With the application of technology, credit risk can be further evaluated with unstructured data model, so that we can not only know the customers better to achieve accurate marketing, but also estimate credit risk more accurately. In combination with the emerging financing method of FinTech, P2P lending will bring a new channel for the financing of SMEs. Moreover, consumer credit loans, low correlated with traditional investment products such as stocks and bonds, provide retail investors a diversified investment instrument.

Context: Chat applications have been around since the beginning of the modern internet. Today, there are many different chat systems with various communication solutions, but only a few utilize the fully decentralized Peer-to-Peer concept. Objectives: In this report, we want to investigate to see if a fully decentralized P2P concept is a suitable choice for chat applications. In order to investigate, a P2P architecture was selected and a simulation was implemented in Java. The simulation was used to make a performance evaluation in order see if the P2P concept could meet the requirements of a chat application, and to identify problems and difficulties. Methods: Two main methods were used in this thesis. First, a qualitative design method was used to identify and discuss different possibilities of designing a distributed chat application. Second, a performance evaluation was conducted to verify the selected and implemented mechanisms are able to obtain their general performance capabilities and to tune them towards anticipated performance. Results: The simulation proved that a decentralized P2P system can scale and find resources in a network quite efficiently without the need of any centralized service. It also proved to be simpler for the user to use the P2P concept, as no special configurations are needed. However, the selected protocol (Chord) had problems with high rates of churn, which could cause problems in big chat environments. The P2P concept was also shown to be highly complex to implement. Conclusion: P2P technology is a more complex technology, but it gives the host a lower cost in terms of hardware and maintenance. It also makes the system more robust and fault-tolerant. As we have seen in this report, P2P can scale and find other resources efficiently without the need of a centralized service. However, it will consume more power for each user, which makes mobile devices bad peers.

An increasing number of applications are becoming more or less network based today. The traditional architecture for network based applications is client-server, but as usage of download services are going up, so is the Peer-to-Peer architecture. This report is a comparison between the Peer-to-Peer and client-server model, and can serve as a basis when a decision between them needs to be taken. In the report, the performance between the different architectures is compared in different contexts. Our basis is a general implementation of both architectures in a test that is derived from a previous report. On top of this, the performance of the different architectures are measured, implemented in a gaming-context. This way, we are trying to give the reader as an objective and informative picture of the different architectures as possible. The tests that have been done shows a different situation than that of the general view, which is that client-server is the preferred model.

Abstract Peer-to-Peer (P2P) networking changes the way of people utilizing Internet, for example, sharing and consuming digital content, from the ground up. It continues to show its power and strength when it is combined with other emerging technologies, such as Web Services. This thesis contributes to the research and development of P2P networks from four aspects. Firstly, a P2P and Web Services converged multiple-tier system architecture is proposed. The architecture proposed enables providing Web Services in the context of heterogeneous access networks in an efficient way by utilizing P2P paradigm. A lightweight middleware architecture is introduced to fit the diversified mobile terminals. A theoretical analysis is given to provide a comparative study with the conventional centralized architecture. Secondly, a General Truncated Pyramid Peer-to-Peer (GTPP) architecture is presented to analyze the performance of hierarchical architecture compared with flat architecture. The motivation behind the GTPP architecture is to see whether an added tier can bring with it added value and functionality. A detailed mathematical analysis is provided which takes into consideration various performance metrics, including the lookup hopcount, lookup latency, maintenance traffic from a single peer point of view, and maintenance traffic from the whole system point of view. Furthermore, simulation results with respect to the lookup hopcount are also provided. Through mathematical analysis and simulation results, an optimal value regarding the number of tiers of the GTPP architecture is found, showing that 2~3 tiers are appropriate for most of situations. A specialized model is also proposed to improve the performance of hierarchical architecture. Thirdly, the performance evaluation of a communication-oriented Kademlia-based P2P system is provided in detail. NetHawk EAST-based simulation models and a prototype are both utilized to evaluate the performance. Simulation results from NetHawk EAST-based simulation models demonstrate the optimal design choices regarding the resource lookup parallelism degree and resource replication degree, and show the unnecessary existence of the messages used to detect the liveness of peers in a DHT overlay. Measurements from the prototype show the feasibility of mobile nodes acting as fully fledged overlay nodes from three different perspectives, namely CPU processing load, network traffic load, and battery consumption. The optimal size of packets which consumes battery in the most efficient way is also found through battery consumption measurements. Fourthly, the effects of different churn models on the performance of structured P2P networks are analyzed. Specifically, three typical churn models are analyzed to provide a comparative result. The simulation results show that the difference among the effects of different churn models on the performance of structured P2P networks is quantitative rather than qualitative. This provides some guidance for the selection of different churn models for the contemporary researchers.