Dans cette thèse nous abordons deux problématiques différentes : la prédiction et la classification de trafic et les mécanismes d'accès dans les réseaux MANETs. Dans la première partie de la thèse, nous abordons le problème de la prédiction et la classification du trafic. Sur la base des observations du passé et sans considérer aucun modèle en particulier, nous analysons le problème de la prédiction en ligne de la charge sur un lien. Concernant la classification du trafic, nous nous concentrons principalement sur des applications P2P, et particulièrement la télévision P2P (P2P-TV). Dans les deux cas, nous employons la technique de Support Vector Machines (SVM). Les algorithmes que nous proposons fournissent des résultats très précis. De plus, ils sont robustes et leur coût est extrêmement bas. Ces propriétés font que nos solutions soient particulièrement adaptées à des applications en temps réel. Dans la deuxième partie de la thèse, nous abordons deux problèmes différents liés aux mécanismes d'accès dans les réseaux MANETs, et en particulier, nous nous concentrons sur CSMA. Nous présentons d'abord les différents modèles existants pour CSMA et nous identifions leurs principaux points faibles. Des solutions possibles sont proposées, bases sur les outils de la géométrie aléatoire. Nous abordons ensuite le problème de QoS dans CSMA et nous proposons deux mécanismes différents permettant de garantir un débit minimum pour chaque transmission admise. Le but principal étant d'identifier le meilleur mécanisme dans un scénario donné comparé au protocole CSMA.

La première partie de cette thèse est dédiée à l’état de l’art sur les réseaux pair-à-pair, la recherche d’information dans de tels réseaux et la problématique de la fouille des données dans le contexte pair-à-pair en se focalisant plus particulièrement sur les méthodes de regroupement (clustering) et les arbres de décision.La seconde partie traite des réseaux où les pairs disposent de leurs propres schémas de données. On y analyse plus particulièrement les fondements et le fonctionnement du système SenPeer. On propose alors une architecture supportant une organisation communautaire des réseaux pair-à-pairs sémantiques. Cela nous permet alors de construire des réseaux pair-à-pair sémantiques structurés en communautés appelés cSON (CommunitySemantic Overlay Network).Ce qui pose alors les questions concernant l’explicitation des communautés et leur exploitation pour améliorer les performances (temps de réponse, nombres de messages, précision et le rappel). Pour construire les communautés, nous étudions deux alternatives différentes : (1) Médiation sémantique : la construction des communautés se base sur les liens sémantiques entre les super-pairs et la confiance qu’ils ont les uns envers les autres et (2) Clustering : un algorithme de clustering basé sur l’analyse des requêtes traitées par les super-pairs est à la base de construction des communautés. Ensuite, nous proposons deux méthodes pour calculer des caractérisations des communautaires en se plaçant dans les deux champs de recherche suivants : (1) Data mining: on cherche à caractériser chaque communauté à l’aide d’une connaissance extraite des requêtes traitées par ses super-pairs d’une même communauté CK (Communauty Knowledge) et (2) Hypergraphes : A l’inverse de la méthode précédente, notre objectif maintenant est de caractériser collectivement les communautés. On formalise ce problème comme la recherche des MCS (minimal covering shortcuts) qui sont des raccourcis, entre les super pairs,minimaux couvrants toutes les communautés. Nous développons ensuite deux méthodes de routages de requêtes CK-rooting et MCS-rooting en utilisant respectivement la connaissance communautaire et les MCS afin d’identifier les super-pairs susceptibles de traiter une requête donnée.Dans la troisième partie, nous présentons le simulateur développé pour supporter l’approche cSON. Nous présentons alors les résultats empiriques résultant de simulations et qui montrent une amélioration significative des performances de l’approche basée uniquement sur la médiation sémantique. Cette partie se termine avec la description d’une application de recherche d’information basée sur le partage de documents scientifiques enrichis. / The first part of this thesis is dedicated to the state of the art on the peer-to-peer networks, the information retrieval in such networks, and the problematic of data mining in the peer-to-peer context more particularly on clustering methods and decision trees.The second part deals with networks where peers have their own data schemas. We examine more particularlythe fundamentals and functioning of the system “SenPeer”. Then, we propose an architecture supporting acommunity organization of semantic peer-to-peer networks. This allows us to build peer-to-peer semantic structured communities called cSON (Communauty Semantic Overlay Network).This raises many questions concerning the explanation of communities and their operating to improve performances (response time, number of messages, precision and recall). To build communities, we study two different alternatives: (1) Semantic Mediation: the building of communities is based on semantic links between super-peers and the confidence that they have between them and (2) Clustering: a clustering algorithm, based onthe analysis of queries processed by the super-peers, is the base of community building. Then, we propose twomethods to calculate the characterizations of communities in the two research fields: (1) Data mining: we try to characterize each community using knowledge extracted from applications processed by his super-peers of the same community CK (Community Knowledge) and (2) Hypergraphs: Unlike the previous method, our goal nowis to characterize the communities collectively. We formalize this problem as the research of the MCS (minimalcovering shortcuts) which are shortcuts between the super-peers, minimum shortcuts covering all communities.Then, we develop two methods of queries routing CK-rooting and MCS-rooting respectively using community knowledge and MCS to identify the super-peers may process a given query.In the third section, we present the simulator developed to support the cSON approach. We present the empirical results representing the simulations and which show a significant improvement of performance of the approachonly based on semantic mediation.This part ends with a description of an application of information retrieval based on sharing enriched scientific documents.

This report has focused on how important a buyers eWOM is compared to his/her visual information when sellers decide if they can trust this buyer. A focus company was Airbnb, an online P2P platform where private individuals can rent out their living quarters to other private persons. The method involved sending out online web surveys to approximately 200 students in Högskolan Kristianstad. Results from these surveys suggests that a buyer’s eWOM and visual information had little or no impact upon if a seller decides to trust this buyer or not. The variable that had the most significant impact upon trust and thus the host’s intention to rent was the variable risk propensity.

This thesis aims to offer a comprehensive analysis of peer-to-peer-based file-sharing by focusing on the discourses about use, agency and motivation involved, and how they interrelate with the infrastructural properties of file-sharing. Peer-to-peer-based file-sharing is here defined as the unrestricted duplication of digitised media content between autonomous end-nodes on the Internet. It has become an extremely popular pastime, largely involving music, film, games and other media which is copied without the permission of the copyright holders. Due to its illegality, the popular understanding of the phenomenon tends to overstate its conflictual elements, framing it within a legalistic 'copyfight'. This is most markedly manifested in the dichotomised image of file-sharers as 'pirates' allegedly opposed to the entertainment industry. The thesis is an attempt to counter this dichotomy by using a more heterodox synthesis of perspectives, aiming to assimilate the phenomenon's complex intermingling of technological, infrastructural, economic and political factors. The geographic context of this study is Sweden, a country characterised by early broadband penetration and subsequently widespread unrestricted file-sharing, paralleled by a lively and well-informed public debate. This gives geographic specificity and further context to the file-sharers' own justificatory discourses, serving to highlight and problematise some principal assumptions about the phenomenon. The thesis thus serves as a geographically contained case study which will have analytical implications outside of its immediate local context, and as an inquiry into two aspects of file-sharer argumentation: the ontological understandings of digital technology and the notion of agency. These, in turn, relate to particular forms of sociality in late modernity. Although the agencies and normative forces involved are innumerable, controversies about agency tend to order themselves in a more comprehensive way, as they are appropriated discursively. The invocation to agency that is found in the justificatory discourses - both in the public debate and among individual respondents - thus allows for a more productive and critically attentive understanding of the phenomenon than previously

Made available in DSpace on 2015-03-05T13:58:26Z (GMT). No. of bitstreams: 0 Previous issue date: 13 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Apesar de ser uma das principais aplicações da Internet na atualidade, o compartilhamento de arquivos P2P tem sido fortemente prejudicado por ataques de poluição de conteúdo. Esta dissertação propõe e analisa uma classe de métodos de contenção de poluição cujo princípio básico é a limitação do número instantâneo de downloads de acordo com a reputação de versões. Inicialmente, o método é proposto e avaliado em termos de um ambiente idealizado, mostrando sua eficiência na contenção de poluição e baixa sobrecarga induzida quando o título não é poluído. A seguir, valendo-se de modelos clássicos para projeto de redes P2P, são propostos e comparados métodos de contenção distribuída / Despite currently one of the main Internet applications, P2P file sharing has been hampered by content pollution attacks. This work proposes and analyzes a class of contention methods to reduce the dissemination of polluted content whose basic principle is to limit the amount of instantaneous downloads according to its reputation. The method is firstly proposed and evaluated in terms of an idealized environment. The evaluation shows the eficiency of the contention method and the low overhead induced when the content is not polluted. Then, inspired by classic P2P designs, we propose and compare distributed contention methods

Made available in DSpace on 2015-03-05T13:58:27Z (GMT). No. of bitstreams: 0 Previous issue date: 16 / Bolsa para curso e programa de Pós Graduação / BitTorrent é a tecnologia de compartilhamento de arquivos mais popular atualmente na Internet e responsável por fração significativa do tráfego nela existente. Considerando sua importância e adoção em larga escala, a arquitetura BitTorrent precisa ser robusta e resistente a pares maliciosos. Esta dissertação constitui a primeira investigação em termos de vulnerabilidades do BitTorrent, apresentando quatro contribuições principais: (a) auxilia no entendimento do BitTorrent; (b) identifica vulnerabilidades e descreve ataques e contramedidas possíveis à arquitetura; (c) descreve um modelo de simulação discreto, que permite mapear o comportamento do protocolo BitTorrent; e (d) avalia, via simulação, o impacto de dois dos ataques identificados, Mentira de Peças e Eclipse. Os resultados mostram que BitTorrent é suscetível a ataques em que pares maliciosos mentem a posse de peças e tornam-nas mais raras, fazendo com que downloads em geral sejam atrasados em até 50%. Em ataques Eclipse, com uma proporção em torno de / BitTorrent is the most popular file sharing technology and associated with a significant fraction of the Internet traffic. Considering its importance and large scale adoption, the BitTorrent architecture should be robust and resistant to malicious peers. This dissertation is the first investigation in terms of vulnerabilities against BitTorrent architecture, providing four important contributions: (a) it helps to increase the understanding of the BitTorrent protocol; (b) it identifies vulnerabilities and describes feasible attacks and countermeasures to the BitTorrent architecture; (c) it presents a discrete event simulation model which maps the behaviour of the protocol; and (d) it evaluates, through simulation, the impact of two proposed attacks, namely Piece Lying and Eclipse. Results show what BitTorrent is vulnerable to cheating peers that lie about having pieces, in order to make them rarer, causing an increase of about 50% in downloading times. Eclipse attacks can cause even more damage, as analysis

Information Communication Systems (ICT) has brought about a change in the way people handle transactions. The payment systems have undergone an incredible evolution over the passing years from physical transfer of cash to exchanging money in a digital form. Mobile Payment (mPayment) which is a branch of mobile commerce is one of the areas that is becoming more and more popular these days. In Sweden, there is a growing success of mPayment system such as SEQR, Swish amongst others. However, a huge chunk of the population is yet to adopt the system. Hence, there is a need to identify factors that influence peoples’ decisions to adopt or not to adopt the mPayment system like Swish. This study aimed at identifying the factors that influence the adoption of mPayment system amongst the consumers in Sweden. The research question was: what factors influence the adoption of Swish mobile payment app among the consumers in Sweden? A qualitative research was conducted. A semi structured interview was used as the data collection method. This data collection method was used because this research work seeks to identify the feelings, opinions and experiences of people and this method fits best into the research work. The thematic analysis approach was used for the data analysis. The study showed that impact of the system on day-to-day activities, speculation of risk and trust of the system, integration to lifestyle, speculation of user friendliness and flexibility, age and peer influence are the factors that influence the adoption of swish mobile payment app amongst the consumers in Sweden. Furthermore, the research was viewed through the lens of the UTAUT by comparing the findings of the study and how it relates to the determinants and moderating factors of the model. In conclusion, this study has contributed to the field of ICT specifically the mobile technology field. The conceptual model that was built will be useful for developers and researchers to be able to know the areas to put in more efforts and areas to keep maintaining. Furthermore, this research was conducted within a country that has experience with m-payment apps. Hence, this study can serve as an example for other countries moving towards higher smartphone and application usage.

Background: Understanding how coherently commitment and basic human values shaping and affecting timebank, one of the popular peer-to-peer exchange system. With time banking, a person with own skill set can trade hours of work for equal hours for another member using hours for paying or being paid for services. Thesis aim: Understanding the impact of drivers/barriers and personal values and how these are connected to the commitment Methodology A quantitative study with forty-seven timebanks across three different country – USA, New Zealand and India. Survey were conducted to collect data and later SPSS has been used for analyzation Findings: Values play significant role to shape commitment to timebank and commitment and personal values has relationship with drivers and barriers of participation in timebank.

網路技術發展的日新月異帶領了眾多新網路服務的崛起，例如即時影音串流這類的多媒體服務。但即時影音串流服務所產生的龐大資料流和傳輸延遲時間的嚴格限制也隨之而來的為網路環境帶來許多挑戰，在這些條件下，傳統Server-client拓樸架構將client要求的影音資料以單一鏈結傳輸時，常會因為頻寬不足而面臨嚴重的封包遺失，或是資料流擁擠造成的額外傳輸延遲使得封包無法達到即時性的需求。P2P網路擁有server-client架構所難以達到的規模伸縮性，且對於節點、鏈結失效所引起的傳輸錯誤也較能容忍，更重要的是，它有效的分散了原本負載在少數link上的龐大資料流。因此P2P架構近年來風行於即時影音串流服務。 目前P2P網路的拓樸多是隨意形成，當網路成員規模龐大時，由傳送端出發到遠方的接收端，途中可能經過無數的鏈結，每一個鏈結都會由於頻寬的不足使得資料流遭受某種程度的品質損害，另一方面，對即時影音服務而言，若資料流的累積延遲時間超出可容忍範圍時，無法為使用者接受。 本研究嘗試找出一個較好的拓樸用以傳輸多媒體資料流，使得位於最遠端節點的累積延遲亦能為使用者接受，且資料品質的損害程度最小。我們將之建置成一NP-Complete複雜度的問題模型，名為MLDST。而解法則是修改Dijkstra single-source shortest-path演算法，並加上每個節點承擔下游節點數量及延遲時間限制而來。我們以PlanetLab環境在實際的網路上進行實驗，證實我們的演算法比傳統的Minimum-Spanning Tree及shortest path spanning tree有更好的影像品質。 / Numerous new network services arise with the advanced development of network technologies, such as real-time multimedia streaming services. But challenges to network environment come along with the enormous traffic of data flows and rigorous restriction to transmission delay of real-time multimedia streaming services. Under this circumstance, conventional server-client topology suffers from serious packet loss and packet delay due to the overload of servers and their accessing links. Also, extra transmission delay may make packets fail to meet the requirement of real-timed services. Peer-to-peer network is more scalable than server-client model, and is much more tolerable to the transmission errors caused by node or link failures. More importantly, it effectively distributes load from the server to peers. As a consequence, peer-to-peer service architecture becomes very popular for real-time multimedia streaming services recently. Peer-to-peer networks are mostly formed in random fashion. As the size of network grows, packets may have to travel through numerous links to reach far-end receivers. The quality of data may be damaged by insufficient bandwidth of links. For real-time multimedia services, it is not acceptable to users if the cumulated packet delay exceeds a tolerable limit. Our research is trying to find a better topology to transmit multimedia data flows which makes the cumulated delay of the most-far-end user be tolerable and the damage of data quality is minimized. The problem is modeled as a MLDST problem, which is a NP-Complete problem. To solve the problem, we modified Dijkstra’s single-source shortest-path algorithm by bounding the node degree and adding delay constraint. The experiments were carried out on real network environment through PlanetLab. Experiments show that our algorithm outperforms traditional MST and shortest path spanning tree.

在vehicular network中應用Peer to peer (p2p)是目前尚在研究的一項領域。不同於一般wired network的環境，vehicular network環境中變動性相當高，且車輛移動速度快，車輛間無法長時間維持連線，所以若要在vehicular network上分享檔案資源，會遭遇到許多問題，像是如何在網路上有效率地搜尋所需要的檔案、相距甚遠的車輛如何分享彼此的資源、在有限的頻寬中如何發揮最大的分享效益，皆是十分重要的課題。本研究提出Urban Multi Layered Chord (UML-Chord)架構，在市區環境的vehicular network中，引入infrastructure-based的架構，以解決ad-hoc環境中只能靠車輛機會相遇時交換訊息，僅能做範圍內搜尋的缺點。另外我們使用multi-layered chord來管理網路上分享的檔案資源，此種結構化的p2p架構可以有比較好的搜尋效率。在檔案傳輸上，我們加入交通號誌的狀況後，讓車輛間連線預估時間(connection lifetime)更加精確，得以選出最適合的節點下載檔案，增加檔案的傳輸效率，提昇整體p2p應用的效能。 / Peer-to-peer (p2p) applications on vehicular network is a significant research topic today .Vehicular network is different from traditional wired network environment in some characteristics. Topology is very dynamic and vehicles driving in high speed, the connection between vehicles can’t maintain in a long time in vehicular network. If we want to share file resources on vehicular network, there are some problems to confronted, like the efficiency of query operations, sharing files with distance vehicles and fully utilizing the limited bandwidth. Our paper proposes an Urban Multi-layered Chord (UML-Chord) method in urban Vehicular network. Introducing infrastructure based architecture to deal with the problem that cars can exchange their files only when they meet each other in ad-hoc mode. In addition, we use multi layered chord to manage file resources which should be shared on Internet. This kind of structured p2p architecture has better efficiency in searching files. For file transfer part, we take stop light into account. We modify connection lifetime, let it be used in choosing appropriated download peers, enhancing the efficiency of p2p application.