In our master thesis, we compare ten classification algorithms for credit scor- ing. Their prediction performances are measured by six different classification performance measurements. We use a unique P2P lending data set with more than 200,000 records and 23 variables for our classifiers comparison. This data set comes from Lending Club, the biggest P2P lending platform in the United States. Logistic regression, Artificial neural network, and Linear discriminant analysis are the best three classifiers according to our results. Random forest ranks as the fifth best classifier. On the other hand, Classification and regression tree and k-Nearest neighbors are ranked as the worse classifiers in our ranking. 1

Η διπλωματική εργασία διαπραγματεύεται την εφαρμοσιμότητα του peer-to-peer υπολογισμού και τεχνικών στα ασύρματα κινητά ad-hoc δίκτυα και στα δίκτυα αισθητήρων. Παρουσιάζεται μια παραλλαγή ενός νέου P2P πρωτοκόλλου (Energy Level Distributed Tree) που σαν κύρια λειτουργία του έχει την αύξηση του προσδόκιμου λειτουργίας ενός δικτύου αισθητήρων. Επίσης, γίνεται αναφορά στα πιο δημοφιλή εργαλεία προσομοίωσης για P2P πρωτόκολλα δρομολόγησης και παρουσιάζεται ένα νέο εργαλείο, d-p2p-sim, με δυνατότητα προσομοίωσης εκατομμυρίων κόμβων. Τέλος, εξετάζουμε την απόδοση ενός νέου P2P πρωτοκόλλου δρομολόγησης, του Nested Balanced Distributed Tree, που απαντά με βέλτιστο τρόπο ερωτήμα ακριβούς ταιριάσματος και ερωτήματα διαστήματος παρουσιάζοντας παράλληλα δύο νέους αλγορίθμους αναζήτησης για αυτό. / In this master thesis we study the applicability of the peer-to-peer computing and techniques on wireless ad-hoc networks and sensor-nets. We propose a simplified mapping of an optimal P2P protocol (NBDT) onto sensor-nets, the so called Energy Level Distributed Tree (ELDT), which has one main operation: the life expectancy of a sensor-net. Furthermore, are examined the most popular Peer-to-Peer simulators and is presented a new distributed simulator for P2P routing algorithms. The key feature of the proposed simulator is the ability to simulate millions of peers. Finally, is presented a revised version of the NBDT protocol which is hot-spot free and achieves a better load distribution introducing a negligible routing overhead.

Abstract Mobile peer-to-peer (P2P) networks have emerged as a substrate for distributed wireless Internet applications. With P2P systems, it is possible to share resources such as data storage space, media files, network bandwidth, or computing power among the devices, which participate in the network, without large and expensive centralised server machines. However, the special characteristics of the mobile environment such as the low computational power, changing network conditions, and limited battery life pose several challenges for the fluent operation of mobile devices in P2P networks; this is also in part affected by the complexity of distributed P2P systems. Software development for mobile devices and the design of mobile networking systems are challenging due to the limited device resources and heterogeneous software platforms. Moreover, the energy consumption of a mobile device, and the network-wide routing efficiency that affects for example the resource lookup performance, depend on multiple variable parameters. P2P application development can be facilitated, however, by using middleware, which hides the complexity of networking from the application programmers. The research contributions of this thesis can be classified into three categories: (1) Novel functionalities of mobile middleware are proposed. One of these is a cross-layer connectivity management framework, which aims to select the best combination of network technology entities in a specific usage situation; the selection is made by logic contained in a replaceable state machine. Another new functionality is a system, which installs a missing application for the user, when the user receives a session request from another user. A signalling system based on the cellular USSD protocol is also presented; the system facilitates the establishment of a P2P connection with a mobile device, whose IP-based network connection is off. Moreover, the suitability of the P2PSIP protocol for implementing wireless distributed services is analysed. (2) P2P-related measurement studies are presented. In them, the message routing efficiency of a P2PP protocol implementation and the network traffic load caused by the messaging are observed, and the energy consumption incurred by the same implementation in a mobile device is measured. In addition, a server-based testbed system used in these measurements is described. (3) Experience-backed guidelines for mobile middleware development are presented. These include practical instructions for software development on a restricted mobile platform, and guidelines and observations related to cross-platform software development. / Tiivistelmä Mobiilit vertaisverkot (P2P) ovat uusi alusta hajautetuille langattomille Internet-sovelluksille. P2P-järjestelmien avulla on mahdollista jakaa resursseja kuten tiedon tallennustilaa, mediatiedostoja, verkon kaistanleveyttä tai laskentatehoa laitteiden kesken, jotka osallistuvat verkkoon, ilman suuria ja kalliita keskitettyjä palvelinkoneita. Mobiiliympäristön erityispiirteet kuten vähäinen laskentateho, vaihtelevat verkko-olosuhteet ja rajallinen akkukesto asettavat kuitenkin useita haasteita sujuvalle mobiililaitteiden vertaisverkkokäytölle; tähän vaikuttaa osaltaan myös hajautettujen P2P-järjestelmien monimutkaisuus. Mobiililaitteiden ohjelmistokehitys ja mobiiliverkkojärjestelmien suunnittelu on haastavaa rajallisten laiteresurssien ja epäyhtenäisten ohjelmistoalustojen vuoksi. Lisäksi mobiililaitteen energiankulutus ja koko P2P-verkon reititystehokkuus, joka vaikuttaa esimerkiksi resurssien hakutehokkuuteen, riippuvat useista muuttuvista parametreista. P2P-sovelluskehitystä voidaan kuitenkin helpottaa käyttämällä välikerrosohjelmistoja, jotka kätkevät verkon käytön monimutkaisuuden sovellusohjelmoijilta. Tämän väitöskirjan tutkimuksellinen uutuusarvo voidaan jakaa kolmeen osa-alueeseen: (1) Uusia toiminnallisuuksia mobiileihin välikerrosohjelmistoihin esitellään. Eräs näistä on verkkokerrosten välinen yhteydenhallintajärjestelmä, jossa pyritään valitsemaan tietyssä käyttötilanteessa paras verkkotekniikoiden yhdistelmä; valinnan tekee vaihdettavien tilakoneiden sisältämä logiikka. Toinen uusi toiminnallisuus on järjestelmä, joka asentaa puuttuvan sovelluksen käyttäjälle, kun käyttäjä saa toiselta käyttäjältä pyynnön ryhtyä yhteysjaksoon tämän kanssa. Myös soluverkkojen USSD-protokollaan perustuva signalointijärjestelmä esitellään; järjestelmän avulla helpotetaan P2P-yhteydenmuodostusta sellaisen mobiililaitteen kanssa, jonka IP-pohjainen verkkoyhteys on poissa päältä. Lisäksi P2PSIP-protokollan soveltuvuutta langattomien hajautettujen palvelujen toteuttamiseen analysoidaan. (2) Esitellään P2P-mittaustutkimuksia. Näissä havainnoidaan P2PP-protokollatoteutuksen viestien reititystehokkuutta ja viestien aiheuttamaa verkkoliikennekuormaa sekä mitataan saman toteutuksen aiheuttamaa energiankulutusta mobiililaitteessa. Lisäksi kuvaillaan mittauksissa hyödynnetty palvelinpohjainen testausjärjestelmä. (3) Esitetään kokemuksiin perustuvia neuvoja mobiilien välikerrosohjelmistojen kehitystyötä varten. Nämä sisältävät käytännöllisiä ohjeita rajoitetulla mobiilialustalla tapahtuvaan ohjelmistokehitykseen sekä neuvoja ja havaintoja liittyen yhtäaikaiseen useiden kohdealustojen ohjelmistokehitykseen.

Botnets are a global problem, and effective botnet detection requires cooperation of large Internet Service Providers, allowing near global visibility of traffic that can be exploited to detect them. The global visibility comes with huge challenges, especially in the amount of data that has to be analysed. To handle such large volumes of data, a robust and effective detection method is the need of the hour and it must rely primarily on a reduced or abstracted form of data such as a graph of hosts, with the presence of an edge between two hosts if there is any data communication between them. Such an abstraction would be easy to construct and store, as very little of the packet needs to be looked at. Structured P2P command and control have been shown to be robust against targeted and random node failures, thus are ideal mechanisms for botmasters to organize and command their botnets effectively. Thus this thesis develops a scalable, efficient and robust algorithm for the detection of structured P2P botnets in large traffic graphs. It draws from the advances in the state of the art in Community Detection, which aim to partition a graph into dense communities. Popular Community Detection Algorithms with low theoretical time complexities such as Label Propagation, Infomap and Louvain Method have been implemented and compared on large LFR benchmark graphs to study their efficiency. Louvain method is found to be capable of handling graphs of millions of vertices and billions of edges. This thesis analyses the performance of this method with two objective functions, Modularity and Stability and found that neither of them are robust and general. In order to overcome the limitations of these objective functions, a third objective function proposed in the literature is considered. This objective function has previously been used in the case of Protein Interaction Networks successfully, and used in this thesis to detect structured P2P botnets for the first time. Further, the differences in the topological properties - assortativity and density, of structured P2P botnet communities and benign communities are discussed. In order to exploit these differences, a novel measure based on mean regular degree is proposed, which captures both the assortativity and the density of a graph and its properties are studied. This thesis proposes a robust and efficient algorithm that combines the use of greedy community detection and community filtering using the proposed measure mean regular degree. The proposed algorithm is tested extensively on a large number of datasets and found to be comparable in performance in most cases to an existing botnet detection algorithm called BotGrep and found to be significantly faster.

This document deals with design, implementation and testing of software system for detecting p2p (peer-to-peer) networks based on combination of BPF prefiltering and POSIX regular expressions packet payload matching with known p2p protocol communications. The proposed detection system includes a database with some rules of most effuse p2p protocols in format resembling to definitions for L7-filter classifier. The application is implemented in C, runs in userspace and is targeted to all POSIX compatible platforms. The combination of detector with user attached QoS controlling is complete solution for traffic reduction of common p2p protocols.

<p>The ever increasing demand for video content directed the focus of researchfrom traditional server-based schemes to peer-to-peer systems for videodelivery. In such systems, video data is delivered to the users by utilizing theresources of the users themselves, leading to a potentially scalable solution.Users connect to each other, forming a p2p overlay network on top of theInternet and exchange the video segments among themselves. The performanceof a p2p system is characterized by its capability to deliver the videocontent to all peers without errors and with the smallest possible delay. Thisconstitutes a challenge since peers dynamically join and leave the overlay andalso contribute different amounts of resources to the system.The contribution of this thesis lies in two areas. The first area is theperformance evaluation of the most prominent p2p streaming architectures.We study the streaming quality in multiple-tree-based systems. We derivemodels to evaluate the stability of a multiple tree overlay in dynamic scenariosand the efficiency of the data distribution over the multiple trees. Then, westudy the data propagation in mesh-based overlays. We develop a generalframework for the evaluation of forwarding algorithms in such overlays anduse this framework to evaluate the performance of four different algorithms.The second area of the thesis is a study of streaming in heterogeneous p2poverlays. The streaming quality depends on the aggregate resources that peerscontribute to the system: low average contribution leads to low streamingquality. Therefore, maintaining high streaming quality requires mechanismsthat either prohibit non-contributing peers or encourage contribution. In thisthesis we investigate both approaches. For the former, we derive a model tocapture the evolution of available capacity in an overlay and propose simpleadmission control mechanisms to avoid capacity drainage. For the latter, inour last work, we propose a novel incentive mechanism that maximizes thestreaming quality in an overlay by encouraging highly contributing peers tooffer more of their resources.</p> / QC 20100506

本論文從對虛擬社群的探問開始，目的是暸解P2P社群的運作方式與其使用者的下載行為，同時也嘗試找尋P2P社群凝聚的要素。這之中包括幾個重要環節須去處理，首先P2P軟體本身的特性以及在這個特性之下P2P社群扮演何種角色，再者下載的資訊如何在P2P社群中流通，除了留意資訊流入的方式外，也可以觀察P2P社群之間亦或整體的P2P場域有什麼樣的規則與默契，最後P2P的使用者如何取得資訊，以及使用者取捨資訊之間、追求下載速度上有何種考量？簡言之，拆解P2P社群運作方式涉及到軟體、社群與使用者三者之間的交互關係；涵蓋巨視面的社群結構及微視面的使用者兩者交錯的影響，因而在進行研究之時，選擇Bourdieu的場域理論來研擬整體的架構。使用「場域」的概念，主要是避免侷限於個別的論壇做為觀察對象，而無法顯現整體P2P社群社運作的缺憾。基於分享概念的P2P軟體，匯聚所有人的資訊與頻寬，才造就如此龐大的影響力，此外，下載「資訊」的流動特徵是一個重要面向，與藉此特性而產生的結構，難以透過對單一的論壇觀察掌握清楚，透過Bourdieu的場域理論將能適切提供分析上的輔助。 P2P軟體發展至今，歷經許多阻礙與轉變，其中最大的挑戰莫過於盜版傳輸的爭議，當然它帶來影響與問題總是相應而生的，因此探討P2P軟體若沒將著作權納入考量，我們難以找出P2P軟體未來發展的可能，並且很可能忽視現有體制的力量，造成推測的結果總是與實際有出入，這部份也是先前研究中不加思索的，除了軟體定位之外，另一個研究的焦點則放在P2P場域的運作邏輯上，它涵括論壇與使用者之間彼此的交互作用。在研究成果的呈現上，第二章將主要處理P2P軟體的定位問題，我們可以發現要跨越著作權的界限，自由軟體提供另一種思考的途徑，它不必然與侵權扯上關係，亦不必屈從著作權的規則，而能保有自己的一片天地。自由軟體替P2P軟體開啟一扇大門，使P2P軟體取得為技術而技術的正當性，在確立P2P軟體的位置之後，依循軟體發展而來的關係將能更加穩固，包括使用其軟體的用戶，能夠維持長期的使用習慣，有機會培養出較具規模的討論社群，並且其中的使用者與論壇部份也成為第三章中所關切的問題，因而，第三章將接續第二章的問題，從使用者的角度來詮釋他們使用軟體時的總總策略，在其策略的選擇與行使當中，便隱約地顯露身處其中的規範。第四章則是總結前兩章節的分析，我們將看到下載行為的背後，事實上，充滿許多複雜的行為動機，並且在追逐下載資訊的同時，使用者將明顯遵循既定的程序來取得檔案，使用的共識與規則，不言而喻地浮現出來。

Šio magistro darbo „File sharing sistemos: autorių teisių aspektai“ objektas yra autorių teisių reglamentavimo ir apsaugos specifika bei problematika P2P programų pagrindu veikiančiose file sharing sistemose. Darbe analizuojama esama teisinė situacija, akcentuojamos probleminės nagrinėjamos temos sritys, lyginant JAV ir ES (tame tarpe ir Lietuvos) autorių teisės doktrinas, principus, esamas teisės normas bei jų pritaikymą teismų praktikoje. Šį darbą sudaro trys dalys. Pirmoje darbo dalyje, atsižvelgiant į aktualius klausimus bei problematiką autorių teisių srityje, pateikiama file sharing sistemų samprata, glaustai paaiškinant šių sistemų technologinį veikimo principą, aptariant pagrindinius sistemų tipus bei apibrėžiant pagrindines sąvokas. Antroje darbo dalyje išsamiai nagrinėjami P2P programų gamintojų (file sharing paslaugų teikėjų) netiesioginės atsakomybės aspektai autorių teisėje, lyginant JAV ir ES teisines pozicijas, kurias formuoja skirtingos teisės doktrinos, teisės normos bei teisminė praktika. Trečioji darbo dalis apima P2P file sharing programų vartotojų tiesioginės atsakomybės už autorių teisių pažeidimus taikymo aspektus, aptariant, kokios išimtinės autorių teisės yra pažeidžiamos naudojantis P2P file sharing programomis bei analizuojant galimas atsakomybės netaikymo išimtis, analogiškai antrajai darbo daliai – lyginant JAV ir ES teisines pozicijas. Trečioje darbo dalyje taip pat trumpai įvertinama esama probleminė situacija bei apsvarstomos galimos problemos... [toliau žr. visą tekstą] / An object of the following Master’s thesis “File sharing systems: the aspects of copyright” is the particularity and problematic of copyright regulation and protection in the file sharing systems performing on the basis of P2P programs. The work analyses the present legal situation, emphasizes the problem areas analyzed by comparing the USA and EU (including Lithuania’s) copyright doctrines, principles, present legal norms and their application in the practice of courts. This Master`s thesis consists of three parts. According to the actual questions and problematic in the field of copyright, the first work part presents the conception of file sharing systems, by briefly explaining the technological performance principle of such systems, describing the main types of systems and defining the main conceptions. The second work part analyses comprehensively the indirect liability aspects of the manufacturers of P2P programs (file sharing services providers) in the copyright law, when comparing the legal positions of the USA and EU, formed by different law doctrines, legal norms and court practice. The third work part includes the application aspects of direct liability for the copyright infringements made by the end-users of P2P file sharing programs, by discussing what exclusive copyrights are infringed when using the P2P file sharing programs, and analyzing the possible liability exceptions; the analysis is made parallel to the second work part – by comparing the USA and EU... [to full text]

Actuellement, nous constatons une augmentation de demande de services vidéo sur les réseaux P2P. Ces réseaux jouent un rôle primordial dans la transmission de contenus multimédia à grande échelle pour des clients hétérogènes. Cependant, le déploiement de services vidéo temps réel sur les réseaux P2P a suscité un grand nombre de défis dû à l’hétérogénéité des terminaux et des réseaux d’accès, aux caractéristiques dynamiques des pairs, et aux autres problèmes hérités des protocoles TCP/IP, à savoir les pertes de paquets, les délais de transfert et la variation de la bande passante de bout-en-bout. Dans ce contexte, l’objectif de cette thèse est d’analyser les différents problèmes et de proposer un mécanisme de transport vidéo temps réel avec le provisionnement de la qualité de Service (QoS). Ainsi, nous proposons trois contributions majeures. Premièrement, il s’agit d’un mécanisme de streaming vidéo adaptatif permettant de sélectionner les meilleurs pair émetteurs. Ce mécanisme permet de structurer les pairs dans des réseaux overlay hybrides avec une prise en charge des caractéristiques sémantiques du contenu et des caractéristiques physiques du lien de transport. Nous présentons ensuite un mécanisme d’ordonnancement de paquets vidéo combiné à une commutation de pairs et/ou de flux pour assurer un transport lisse. Finalement, une architecture de collaboration entre les applications P2P et les fournisseurs de services / réseaux est proposée pour supporter un contrôle d’admission de flux. / There is an increasing demand for scalable 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 large-scale transmission of multimedia content to heterogeneous clients. However, the deployment of real-time video streaming applications over P2P networks arises lot of challenges due to heterogeneity of terminals and access networks, dynamicity of peers, and other problems inherited from IP network. Real-time streaming applications are very sensitive to packet loss, jitter / transmission delay, and available end-to-end bandwidth. These elements have key importance in QoS provisioning and need extra consideration for smooth delivery of video streaming applications over P2P networks. Beside the abovementioned issues, P2P applications lack of awareness in constructing their overlay topologies and do not have any explicit interaction with service and network providers. This situation leads to inefficient utilization of network resources and may cause potential violation of peering agreements between providers. The aim of this thesis is to analyze these issues and to propose an adaptive real-time transport mechanism for QoS provisioning of Scalable Video Coding (SVC) applications over P2P networks. Our contributions in this dissertation are threefold. First, we propose a hybrid overlay organization mechanism allowing intelligent organization of sender peers based on network-awareness, media- awareness, and quality-awareness. This overlay organization is further used for an appropriate selection of best sender peers, and the efficient switching of peers to ensure a smooth video delivery when any of the sender peers is no more reliable. Second, we propose a packet video scheduling mechanism to assign different parts of the video content to specific peers. Third, we present a service provider driven P2P network framework that enables effective interaction between service / network providers and P2P applications to perform QoS provisioning mechanism for the video streaming.

Peer-to-peer networks are a common methodology used for content delivery and data sharing on the Internet. The duration of any particular download session is highly dependent on the capacity of the node servers selected as source peers. Recent investigations have shown that specific total download times may deviate significantly from average total download times. This work investigates a novel approach to selecting download server peers that is intended to reduce average total download times and minimize variance of those times from the overall average of download session durations. Typical algorithms used in today's Peer-to-Peer (P2P) systems have improved from simply connecting to a single source peer for the entire download session to an approach where the download content is divided into chunks and a randomly selected source peer is chosen as the source for each chunk. This limits the possibility of an extremely long download session due to the selection of a low capacity download source peer. Prior work has demonstrated that it is better to divide the download session into time slices and download as much as possible from a randomly selected source peer within each time interval rather than staying connected to a poorly performing source peer for the entire time it takes to download a chunk of the source content. This approach minimizes the time spent with a poorly performing source peer and allows the client to move on to a potentially better performing source after a specific, limited interval. Other work has shown that by keeping a history of node performance, it is possible to recognize a poorly performing partner early in a time slice and depart to a new, and hopefully better performing partner, prior to the completion of a time slice (referred to as "choking" a poorly performing peer). These approaches have been shown to reduce average download times and minimize the variance in duration between download sessions. Prior work has also shown that there is value in the use of parallel download streams. As long as the number of streams is kept small (i.e. 4 to 6), minimizing the overhead of maintaining numerous streams and saturation of the available incoming network bandwidth, average download time can be further reduced. The algorithm described in this investigation uses time-based source peer switching and maintains a small number of parallel download streams. At the end of each time interval, it does not randomly replace all source peers but keeps those source peers that are performing relatively better and replaces those performing relatively poorly with randomly selected new source partners. In this way, as the download progresses, parallel downloading typically progresses from a set of better and better performing source partners, therefore reducing average download times and reducing overall variance between download times. This approach has been shown in simulations to reduce average download times by nearly 20% over parallel versions of basic time-based downloads and 8.7% over time-based downloads with the addition of "choking" poorly performing partners. As file sizes increase and/or the heterogeneity of source node service capacities increase, the benefits of this approach to source peer replacement also increases. These improvements are gained while maintaining or further limiting the variance in performance between download sessions. The reduction in average download times and the decrease in variance between download sessions provided by this approach will improve the user experience for users of P2P content distribution systems. This approach should also be applicable to other data distribution systems such as distributed file systems.