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BitTorrent is a popular peer-to-peer file sharing system and a target file shared through BitTorrent is partitioned into pieces and downloaded from multiple peers in parallel in order to shorten the download process. However, due to peer dynamics in P2P networks, rare pieces may be lost and thus lead to the so-called last piece problem. BitTorrent employs rarest-first piece selection algorithm to deal with this problem, but its efficacy is limited because each peer only has a local view of piece rareness. In this paper, we propose an Interest-Intended Piece Selection (IIPS) algorithm aiming at better alleviating the last piece problem while maintaining stable cooperation between peers. IIPS is named interest intended in that every IIPS peer favors pieces that, if downloaded, would increase the probability of being interesting to its cooperating peers. Simulation results show that IIPS achieves less occurrences of piece loss under tough conditions and slightly outperforms the BitTorrent's rarest-first algorithm in terms of higher piece diversity.

The Internet continually evolves in scope and complexity, with the wide deployment of more capacity backbone links and IPv6, the emergence of streaming applications, and even the rapid changing nature of the same applications. These changes lead us to question how is the evolution trend as well as present situation of IPv6 users on the most popular Internet applications (such as Bittorrent). To tackle this issue, we conducted this measurement study on a private BitTorrent System, which is deployed over a campus network serving more than 25,000 users with three external links connecting to Telecom, CERNET, and CERNET2 (IPv6). With packet traces collected from external links and the 10-month log files from the private tracker, we first provide amount and components of IPv6 traffic, and compared with those of IPv4 traffic, then present in depth measurement and analysis from users group evolution, each group’s status, and level of activity.

BitTorrent is a widely used protocol for peer-to-peer (P2P) file sharing, including material which is often suspected to be infringing content. However, little systematic research has been undertaken to establish to measure the true extent of illegal file sharing. In this paper, we propose a new methodology for measuring the extent of infringing content. Our initial results indicate that at least 89.9% of files shared contain infringing content, with a replication study on another sample finding 97%. We discuss the limitations of the approach in this case study, including sampling biases, and outline proposals to further verify the results. The implications of the work vis-a-vis the management of piracy at the network level are discussed.

This paper reveals the power saving potential of P2P file sharing in two cases; popular and unpopular files. For popular files, we derive, with regard to BitTorrent, an expression for the optimal time seeders should support leechers. For unpopular files, we extend an existing model by taking into account leechers’ power consumption dependent on the load. Leechers are assumed to build a temporary cluster within the P2P-overlay. We determine the required number of active leechers to cope with a given load and compare results from an analytical model to simulation. We demonstrate that it is possible to reach almost optimal energy efficiency for the download scenario by comparing the local case without cooperation with the distributed case where leechers cooperate.

Many researches on peer-to-peer video streaming have focused on dealing with highly dynamic, high-churn P2P environment. Most of P2P streaming protocols were modified from a P2P file sharing protocol. Inspired by the high performance on peer-to-peer file sharing of BitTorrent, we propose an overlaying streaming mechanism on the native BitTorrent protocol and realize a practical P2P video streaming service, called WuKong. WuKong not only takes advantages of BitTorrent but also combines the video scalability of layered video coding. In this paper, we depict an overlaid streaming mechanism in WuKong and an adaptive layer-downloading process to balance between the video quality and bandwidth utilization on heterogeneous peers. WuKong is carried out by using an open-sourced library of the BitTorrent protocol, coding schemes of the Windows Media Video (WMV), and the Scalable Video Coding (SVC). We measured and compared the service quality of end-users served by WuKong on heterogeneous peers. In addition, we evaluated the effectiveness of WuKong with peers that are randomly joining and leaving the P2P network. The results show that WuKong not only provides high quality P2P video streaming services but also supports different scaling abilities over heterogeneous devices.

The popularity of Peer-to-Peer (P2P) Internet communication technologies being exploited to aid cybercrime is ever increasing. P2P systems can be used or exploited to aid in the execution of a large number of online criminal activities, e.g., copyright infringement, fraud, malware and virus distribution, botnet creation, and control. P2P technology is perhaps most famous for the unauthorised distribution of copyrighted materials since the late 1990’s, with the popularity of file-sharing programs such as Napster. In 2004, P2P traffic accounted for 80% of all Internet traffic and in 2005, specifically BitTorrent traffic accounted for over 60% of the world’s P2P bandwidth usage. This paper outlines a methodology for investigating a documented P2P network, BitTorrent, using a sample investigation for reference throughout. The sample investigation outlined was conducted on the top 100 most popular BitTorrent swarms over the course of a one week period.

Internet file sharing via the use of peer-to-peer networks is an activity that has been growing steadily for several years. It has rapidly become the most widespread method for the exchange of digital material and as a result raises much controversy. The current, most popular protocol in this field is BitTorrent. Although it is relatively simple in most cases to link particular file sharing activities to an IP address, this does little to prove that a particular user was responsible for using the connection. This study explores three popular BitTorrent client applications, BitComet, Vuze and @mTorrent and outlines the registry artefacts that are produced by the installation and use of these programs on a Windows 7 client. These artefacts are examined in detail to establish what useful evidence, if any, can be recovered from them. Relevant information is highlighted for each application.

It has become apparent for quite some time that the Internet has evolved from a network connecting pairs of end-hosts to a substrate for information dissemination. While this shift towards information centric networking has been clearly demonstrated by the proliferation of file sharing and content delivery applications, it has not been reflected in a corresponding shift in network architecture. To address this issue, we designed MultiCache, an information-centric architecture aiming at the efficient use of network resources. MultiCache is based on two primitives: multicast and caching. It exploits overlay multicast as a means for content delivery and takes advantage of multicast forwarding information to locate, in an anycast fashion, nearby caches that have been themselves fed via multicast. We evaluate MultiCache against a widespread file sharing application (BitTorrent) with respect to both network resource consumption and end-user experience.

International audience; Peer-to-peer (P2P) locality has recently raised a lot of interest in the community. Indeed, whereas P2P content distribution enables financial savings for the content providers, it dramatically increases the traffic on inter-ISP links. To solve this issue, the idea to keep a fraction of the P2P traffic local to each ISP was introduced a few years ago. Since then, P2P solutions exploiting locality have been introduced. However, several fundamental issues on locality still need to be explored. In particular, how far can we push locality, and what is, at the scale of the Internet, the reduction of traffic that can be achieved with locality? In this paper, we perform extensive experiments on a controlled environment with up to 10,000 BitTorrent clients to evaluate the impact of high locality on inter-ISP links traffic and peers download completion time. We introduce two simple mechanisms that make high locality possible in challenging scenarios and we show that we save up to several orders of magnitude inter-ISP traffic compared to traditional locality without adversely impacting peers download completion time. In addition, we crawled 214,443 torrents representing 6,113,224 unique peers spread among 9,605 ASes. We show that whereas the torrents we crawled generated 11.6 petabytes of inter-ISP traffic, our locality policy implemented for all torrents could have reduced the global inter-ISP traffic by up to 40%.

Peer-to-Peer protocols currently form the most heavily used protocol class in the Internet, with BitTorrent, the most popular protocol for content distribution, as its flagship. A high number of studies and investigations have been undertaken to measure, analyse and improve the inner workings of the BitTorrent protocol. Approaches such as tracker message analysis, network probing and packet sniffing have been deployed to understand and enhance BitTorrent's internal behaviour. In this paper we present a novel approach that aims to collect, process and analyse large amounts of local peer information in BitTorrent swarms. We classify the information as periodic status information able to be monitored in real time and as verbose logging information to be used for subsequent analysis. We have designed and implemented a retrieval, storage and presentation infrastructure that enables easy analysis of BitTorrent protocol internals. Our approach can be employed both as a comparison tool, as well as a measurement system of how network characteristics and protocol implementation influence the overall BitTorrent swarm performance. We base our approach on a framework that allows easy swarm creation and control for different BitTorrent clients. With the help of a virtualized infrastructure and a client-server software layer we are able to create, command and manage large sized BitTorrent swarms. The framework allows a user to run, schedule, start, stop clients within a swarm and collect information regarding their behavior., ISSN - [Online: 0974 - 9322; Print : 0975- 2293], pages 52-65

Locality awareness is considered as a promising approach to increase the efficiency of content distribution by peer-to-peer (P2P) networks, e.g., BitTorrent. It is intended to reduce the inter-domain traffic, which is costly for Internet service providers (ISPs), and to simultaneously increase the performance from the viewpoint of P2P users, i.e., to shorten download times. This win-win situation should be achieved by a preferred exchange of information between peers which are located close to each other in the underlying network topology. A set of studies shows that these approaches can lead to a win-win situation under certain conditions, and to a win-no lose situation in most cases. However, the scenarios used mostly assume homogeneous peer distributions. This is not the case in practice according to recent measurement studies. Therefore, we extend previous work in this paper by studying scenarios with real-life, skewed peer distributions. We show that even a win-no lose situation is difficult to achieve under those conditions and that the actual impact for a specific peer heavily depends on the used locality-aware peer selection and the specific scenario. This contradicts the principle of economic traffic management (ETM), which aims for a solution where all involved players benefit and consequently have an incentive to adopt locality awareness. Therefore, we propose and evaluate refinements of current proposals, allowing all users of P2P networks to be sure that their application performance is not reduced. This mitigates the unfairness introduced by current proposals which is a key requirement for a broad acceptance of the concept of locality awareness in the user community of P2P networks.

A peer to peer (P2P) computer network relies on direct connections between participants instead of conventional centralized resources. This kind of network is useful for many purposes, but its killer application nowadays is file sharing. BitTorrent is a very popular protocol for this matter. In this paper, we model a BitTorrent network as a multi-agent system. In it, each BitTorrent client is an agent that interacts with other agents and reacts autonomously, following the same decision algorithms as a real client. The clients aim at downloading content files in the shortest time possible and they share them with other agents. The model is programmed in JADE, a software framework in Java language for agent development. The model has been validated by initial tests, and it will be used to study the behavior of BitTorrent networks in diverse situations that are hard to emulate in a real network, or to simulate with other models, like modifications of the protocol or user behaviors.

Recently, video streaming services using P2P (Peer-to-Peer) have attracted attention to solve the problem of load concentration on servers and to reduce large latency. Many P2P streaming systems, like Coolstreaming, however, take a complicated approach to control playback timing severely. This leads to less churn resiliency and less adaptability to fluctuation of network traffic. Therefore, we focus on a simple and robust approach to realize “pseudo” streaming with high quality, which is based on BitTorrent. In the existing methods with the simple approach, peers download pieces just closer to playback timing to decrease the playback discontinuity. However, these methods do not consider the constitution of video structure in sophisticated manner. P2P streaming system must consider several important metrics for high-quality and fair distribution. Therefore, in this paper, we propose a new P2P video streaming system considering the cooperation of three important metrics; video structure, playback timing, and piece dispersion on network. In this system, users vary three piece selections to suit the delivery status. Specifically, users preferentially download pieces which affect the video quality, which are closer to playback timing, and which improve the delivery efficiency. Moreover, we show the effectiveness of the proposed method by computer simulation.

The P2P applications tend to be important in nowadays Internet, and BitTorrent(BT) is one of the most popular P2P applications. This paper analyzes the distribution of BitTorrent seeds and its properties with the data measured from the Web server of BitTorrent. The Gini coefficient is introduced as the index of the distribution of the seeds in BitTorrent system to demonstrate the evolution of the seed distribution. The Largest Lyapunov exponent is also employed to analyze the stability of the emergent structure of the seeds. The results show that in a BitTorrent system the seed distribution is not inequality, but its evolution is steady and the inequality doesn’t enlarge with the participants’ increasing.

Infrastructure-as-a-Service (IaaS) cloud computing is emerging as a viable alternative to the acquisition and management of physical resources. The new main feature of IaaS cloud computing is the virtual machine (VM) technology which improves the flexibility of resource management. VMs use virtual machine images that are preconfigured and ready to run. Typically, VM image management uses local file copy and distribution via a network file system (NFS). This potentially means that a more efficient method can be used for VM image distribution. For efficient VM image management, we have designed and implemented a BitTorrent-based network block device (namely, BitNBD) for provisioning VM images in IaaS clouds. The BitNBD mainly provides a ‘split read/write mechanism’ to deal with concurrent VM instances where the same pieces of a VM are shared. With respect to the legacy BitTorrent protocol, the BitNBD enhances the piece picker policy and energy-saving mode. It is very effective in minimizing VM startup delays and providing a hibernating capability.

The paper reports on a detailed study of the BitTorrent content distribution system. We first present a measurement infrastructure designed to allow detailed, message-level capture and analysis of P2P traffic. An associated modeling methodology is presented as well. These tools have been used to measure and model the BitTorrent protocol, which is observed to exhibit exponential characteristics of session interarrival times. We also observe that session durations and sizes are modeled with a log-normal distribution.

In an n-way broadcast application, each one of n overlay nodes wants to push its own distinct large data file to all other n-1 destinations as well as download their respective data files. BitTorrent-like swarming protocols are ideal choices for handling such massive data volume transfers. The original BitTorrent targets one-to-many broadcasts of a single file to a very large number of receivers, and thus, by necessity, employs a suboptimized overlay topology. n-way broadcast applications, on the other hand, owing to their inherent complexity, are realizable only in small to medium scale networks. In this paper, we show that we can leverage this scale constraint to construct optimized overlay topologies that take into consideration the end-to-end characteristics of the network and as a consequence deliver far superior performance compared to random and myopic (greedy) approaches. We present the Max-Min and Max-Sum peer-selection policies used by individual nodes to select their neighbors. The first one strives to maximize the available bandwidth to the slowest destination, while the second maximizes the aggregate output rate. We design a swarming protocol suitable for n-way broadcast and operate it on top of overlay graphs formed by nodes that employ Max-Min or Max-Sum policies. Using measurements from a PlanetLab prototype implementation and trace-driven simulations, we demonstrate that the performance of swarming protocols on top of our constructed topologies is far superior to the performance of random and myopic overlays.

Despite persistent government and industry efforts to stop the sharing and downloading of media such as files over peer-to-peer (P2P) networks, this activity shows no sign of abating. This research investigated whether psychological reactance could account for variance in the intent to engage in, and the extent of such behaviour beyond that accounted for by the standard Theory of Planned Behaviour (TPB) variables. No support for psychological reactance as a predictor of P2P file downloading intent or behaviour was found in this paper. However, the results did indicate that attitude, subjective norms, and perceived behavioural control each accounted for significant variance in P2P file downloading behaviour, and that these relationships were fully mediated by behavioural intent. These findings are consistent with, and provide strong support for, the use of the TPB within this domain.

BitTorrent has emerged as an effective peer-to-peer application for digital content distribution in the Internet. However, selecting peers in BitTorrent for efficient content distribution still poses a number of challenges due to high heterogeneities of peers with varied rates of uploading bandwidth and dynamic content. This paper presents GA-BT, a genetic algorithm based peer selection optimization strategy for efficient content distribution in BitTorrent networks taking into account both the uploading bandwidth of peers and the availability of content among peers. GA-BT employs the divisible load theory to dynamically predict optimal fitness values to speed up the convergence process in producing optimal or near optimal solutions in peer selection. A BitTorrent simulator is implemented for GA-BT performance evaluation, and the experimental results show the effectiveness of GA-BT in peer selection optimization.

BitTorrent was long believed to be robust to free-riding behavior. Yet, some recent studies show that misbehaving peers download far more than they upload and free riders even upload nothing at all. In order to guarantee the upload fairness among peers, this paper proposes a quota-based encrypted block trading protocol (Quota-Encryption for short). The basic idea is for peers to prepay a ''quota'' of encrypted blocks to each other and then to alternately reveal decryption keys. Simulation results show that it guarantees better upload fairness among peers, making the free-riding behavior impossible in BitTorrent.

The user experience for networked applications is becoming a key benchmark for customers and network providers. Perceived user experience is largely determined by the frequency, duration and severity of network events that impact a service. While today's networks implement sophisticated infrastructure that issues alarms for most failures, there remains a class of silent outages (e.g., caused by configuration errors) that are not detected. Further, existing alarms provide little information to help operators understand the impact of network events on services. Attempts to address this through infrastructure that monitors end-to-end performance for customers have been hampered by the cost of deployment and by the volume of data generated by these solutions. We present an alternative approach that pushes monitoring to applications on end systems and uses their collective view to detect network events and their impact on services - an approach we call Crowdsourcing Event Monitoring (CEM). This paper presents a general framework for CEM systems and demonstrates its effectiveness for a P2P application using a large dataset gathered from BitTorrent users and confirmed network events from two ISPs. We discuss how we designed and deployed a prototype CEM implementation as an extension to BitTorrent. This system performs online service-level network event detection through passive monitoring and correlation of performance in end-users' applications.

The investigation of peer-to-peer (p2p) file sharing networks is now of critical interest to law enforcement. P2P networks are extensively used for sharing and distribution of contraband. We detail the functionality of two p2p protocols, Gnutella and BitTorrent, and describe the legal issues pertaining to investigating such networks. We present an analysis of the protocols focused on the items of particular interest to investigators, such as the value of evidence given its provenance on the network. We also report our development of RoundUp, a tool for Gnutella investigations that follows the principles and techniques we detail for networking investigations. RoundUp has experienced rapid acceptance and deployment: it is currently used by 52 Internet Crimes Against Children (ICAC) Task Forces, who each share data from investigations in a central database. Using RoundUp, since October 2009, over 300,000 unique installations of Gnutella have been observed by law enforcement sharing known contraband in the the U.S. Using leads and evidence from RoundUp, a total of 558 search warrants have been issued and executed during that time.

BitTorrent is a popular peer-to-peer (P2P) file-sharing protocol that utilizes a central server, known as a ‘tracker’, to coordinate connections between peers in a ‘swarm’, a term used to describe a BitTorrent ad-hocfile sharing network. The tracker of a swarm is specified by the original file distributor and trusted unconditionally by peers in the swarm. This central point of control provides an opportunity for a file distributor to deploy a modified tracker to provide peers in a swarm with malicious coordination data, directing peer connection traffic toward an arbitrary target machine on an arbitrary service port. Although such an attack does not generate huge amount of attack traffic, it would set up many connections with the victim server successfully, which could cause serious denial-of-service by exhausting the victim server's connection resource. In this paper, we present and demonstrate such an attack that is entirely tracker-based, requiring no modifications to BitTorrent client software and could be deployed by an attacker right now. The results from both emulation and real-world experiments show the applicability of this attack. Due to the skyrocketing popularity of BitTorrent and numerous large-scale swarms existed in the Internet, BitTorrent swarms provide an intriguing platform for launching distributed denial-of-service (DDoS) attacks based on connection exhaustion. Copyright © 2010 John Wiley & Sons, Ltd.

BitTorrent, the most popular P2P file sharing application over the Internet, has also been widely used for video file distribution, albeit in a download-and-play mode. In this paper, we extensively examine the characteristics of BT swarms with different contents through a large-scale measurement. Our study especially focuses on the existing video file swarms, trying to understand the potentials and challenges of providing streaming service in BitTorrent. Our results from intra-swarm, inter-swarm and AS-level measurements demonstrate that the video file swarms in the BitTorrent system are quite different from the non-video swarms. In particular, the preference bias terminates the long-term relationship between peers and raises a significant challenge to develop BT based streaming service. Fortunately, we find that most peer sets in video file swarms are good enough to support streaming service. Strong relationship between video file swarms is also observed from the inter-swarm measurement. This inter-swarm relationship can provide extra peer information for video file swarms. Therefore, the organization of existing peer information could be the key to mitigate the preference bias. To this end, a hypercomplex based virtual channel mechanism is proposed. We find that, quaternions can provide efficient and meaningful approximation in the bitfield operations. Using quaternion based three space rotation, our approach can help peers to avoid preference bias during the data delivery. This is especially helpful at the beginning of the downloading since the peer only has few local pieces. More importantly, this mechanism is transparent and friendly to the existing BT swarms with both video and non-video contents.

The fast-growing traffic of peer-to-peer applications, most notably BitTorrent, is putting unprecedented pressure to Internet service providers. Understanding the peer distribution over the global Internet thus becomes critical toward building new generation of ISP-friendly peer-to-peer systems. There are unfortunately significant scalability and representability challenges in measuring and understanding realworld peer distribution. In this article we demonstrate a novel hybrid measurement methodology that uses the PlanetLab as a distributed probing platform to interact with BitTorrent trackers and peers in the global Internet. Our design achieves fast real-time scanning of genuine online peers; yet we carefully avoid the potential copyright infringement and traffic overhead for PlanetLab. From three months? data of over 9 million peers, we identify fundamental issues in conventional traffic locality designs, and also shed new light on re-engineering trackers and reusing historically downloaded data to make BitTorrent a better storage system.

BitTorrent nowadays is one of the most important peer-to-peer (P2P) file-sharing applications on the Internet, and it has also inspired many other P2P applications such as live or on-demand video streaming services. On the other hand, Network Address Translation (NAT) has become pervasive in almost all networking scenarios, from residential Internet access to enterprise networks. Despite the effort of NAT traversal, it is still very likely that P2P applications cannot receive incoming connection requests properly if they are behind NAT. To quantify the performance impact of NAT on BitTorrent-like P2P systems, we have created and validated a detailed but tractable mathematical model. We have also proposed and briefly examined a simple but effective strategy to mitigate the negative impact on NAT peers. In this paper, we further extend our model to cover the proposed biased optimistic unchoke strategy, and optimize the system performance in terms of both average peer download time and system finish time. We also create a new, faster Java-based BitTorrent simulator, which is used to validate the extended model and show the optimality of the proposed strategy and its boundary conditions.

Peer-to-peer (P2P) data networks dominate Internet traffic, accounting for over 60% of the overall traffic in a recent study. In this work, we study the problems that arise when mobile hosts participate in P2P networks. We primarily focus on the performance issues as experienced by the mobile host, but also study the impact on other fixed peers. Using BitTorrent as a key example, we identify several unique problems that arise due to the design aspects of P2P networks being incompatible with typical characteristics of wireless and mobile environments. Using the insights gained through our study, we present a wireless P2P client application that is backward compatible with existing fixed-peer client applications, but when used on mobile hosts can provide significant performance improvements.

A distinct trend has emerged that the Internet is used to transport data on a more and more massive scale. Capacity shortage in the backbone networks has become a genuine possibility, which will be more serious with fiber-based access. The problem addressed in this paper is how to conduct massive content distribution efficiently in the future network environment, where the capacity limitation can equally be at the core or the edge. We propose a novel technique as a main content transport mechanism to achieve efficient network resource utilization. The technique uses multiple trees for distributing different file pieces, which at the heart is a version of swarming. In this paper, we formulate an optimization problem for determining an optimal set of distribution trees as well as the rate of distribution on each tree under bandwidth limitation at arbitrary places in the network. The optimal solution can be found by a distributed algorithm. The results of the paper not only provide stand-alone solutions to the massive content distribution problem, but should also help the understanding of existing distribution techniques such as BitTorrent or FastReplica.

In the past few years, there have been tremendous interest in the peer-to-peer(P2P) content delivery. This communication paradigm dramatically increases the traffic over inter-ISP links. In particular, BitTorrent(BT), the most popular P2P application, generates a huge amount of traffic on the Internet. BitTorrent’s performance is limited by the fact that typical internet users have much lower upload bandwidths than download bandwidths. This results in the overall average download speed of a BitTorrent-like file download system to be bottle-necked by the much lower upload capacity. We think about to utilize idle users’ spare upload capacity to largely improve the download speed beyond what can be achieved in a conventional BitTorrent network. In this paper, we design a system that is completely compatible with the already existing clients who conform to the BitTorrent protocol, at the same time, we analyze this system’s steady-state performance and present simulation results.

P2P systems are becoming the dominator of Internet. Such systems are typically composed of thousands to millions of physical computers, which make it difficult to predict their behaviors without a large scale distributed system simulator. This paper is an attempt to predict the behavior of large scale P2P systems by building a novel parallel simulator: AegeanSim, which provides parallel discrete event simulation of such systems on high performance server clusters. We abstract the execution of P2P applications with a specific event model, and parallel the simulation of events in a cluster, thus expanding the simulation scale and boosting the simulation process dramatically. A 1-stage synchronization method is proposed to improve the performance. An event callback interface is designed to implement their application logic easily while keeping the simulator application-independent. We use AegeanSim to predict the behavior of a typical P2P system: BitTorrent. By comparing the simulation behavior of BT with that of related BT studies and verifying its efficiency, scalability and accuracy, we make predictions about the behavior of BT system assuming they are assaulted by different man-made system attacks. Some reasonable results are found: (1) Tracker isolation can hardly work because of its short attacking time window. (2) Limiting the bandwidth of BT may be an efficient way to control it.

Peer-to-peer (P2P) swarm technologies have been shown to be very efficient for large scale content distribution systems, such as the well-known BitTorrent and eMule applications. However, these systems have been designed for generic file sharing with little consideration of media streaming support, and the user cannot start a movie playback before it is completely downloaded. The playing-as-downloading capability would be particularly useful for a downloading peer to evaluate if a movie is valuable to be downloaded, and it could also help the P2P content distribution system to locate and eliminate the polluted contents. In this paper we address this issue by introducing a new algorithm, wish driven chunk distribution (WDCD), which enables the P2P file sharing system to support the video-on-demand (VOD) function while keeping the P2P native downloading speed. A new parameter named next-play-frequency is added to the content chunk to strike a replication balance between downloading and streaming requests. We modify the eMule as the test bed by adding the WDCD algorithm and then verify the prototype implementation by experiments. The experimental results show that the proposed algorithm can keep the high downloading throughput performance of the eMule system with a good playing-as-downloading function.

Recent studies have shown that the Internet-related energy consumption represents a significant, and increasing, part of the overall energy consumption of our society. Therefore, it is extremely important to look for energy-efficient Internet applications and protocols. The largest contribution to this energy consumption is due to Internet edge devices (PCs and data centers). As a particularly significant example, in this paper we address the fact that users leave their PCs continuously powered on for satisfying connectivity requirements of Peer-to-Peer (P2P) file sharing applications, like BitTorrent (currently the most popular P2P Internet platform). To reduce these energy consumptions, without penalizing the Quality of Service of BitTorrent users, in this paper we propose a novel architecture based on the introduction of a BitTorrent proxy. BitTorrent users delegate the download operations to the proxy and, then, power off their PC, while the proxy downloads the requested files. We implemented our solution and validated it in a realistic testbed. Experimental results show that, with respect to the legacy BitTorrent approach, our solution is very effective in reducing the energy consumption without introducing any QoS degradation. Specifically, our results show that the proxy-based solution can provide up to 95% reduction in the energy consumption and, at the same time, a significant reduction in the average file download time.

In this paper, a hybrid approach for identifying the traffic running over BitTorrent (BT) protocol is proposed. Besides the conventional port-based and signature-based methods, another two BT-oriented methods dealing with the peer-information and flow-information of BT traffic are also adopted. The peer-information method makes use of the unencrypted peer-transfer mechanism of BT protocol, and the flow-information method focuses on identifying the encrypted traffic, which evades the above three methods, with low false-positive ratio. The preliminary evaluation shows that our hybrid approach is effective and comprehensive for BT traffic identification.

Since its inception, BitTorrent has proved to be the most popular approach for sharing large files using the peer-to-peer paradigm. BitTorrent introduced several innovative mechanisms such as tit-for-tat (TFT) and rarest first to enable efficient distribution of files among the participating peers. Several studies examining the performance of BitTorrent and its mechanisms have been published in the literature. In this paper, we present a survey of performance studies of BitTorrent from 2003 to 2008. We categorize these studies based on the techniques used, the mechanisms studied and the resulting observations about BitTorrent performance. Many of the performance studies also suggested modifications to BitTorrent's mechanisms to further improve its performance. We also present a survey of the suggested improvements and categorize them into different groups.

Measuring and characterizing peer-to-peer (P2P) file-sharing systems will benefit the optimization and management of P2P systems. Though there are a lot of measurement studies on BitTorrent almost in every important aspect, few of them focus on the measurement issues and the corresponding solutions, which can strongly influence the accuracy of measurement results. This paper analyzes the key difficulties of measuring BitTorrent and presents a measurement system with combination of active and passive ways, which can han-dle with the problems well and balance the efficiency and integrity. Then compared to other work, a more complete and representative measurement was performed for nearly two months and several characteristics are concerned: 1) there are diverse content sharing in BitTorrent system, but multimedia files that are larger than 100 MB are the most. 2) Distributed Hash Tables has indeed enhanced the ability of peer discovery though there are some pitfalls to be addressed. 3) Pieces are distributed uniformly after the early stage and there are few rare pieces. Furthermore, peer arrival rate shows a periodical pattern, which was not well mod-eled before. Then an improved model is proposed and the experiment results indicate that new model is fitted in with actual measurement results with high accuracy.

Content distribution via the Internet is becoming increasingly popular. To be cost-effective, commercial content providers are now using peer-to-peer (P2P) protocols such as BitTorrent to save bandwidth costs and to handle peak demands. When an online content provider uses a P2P protocol, it faces an incentive issue: how to motivate its clients to upload to their peers. This paper presents Dandelion, a system designed to address this issue. Unlike previous incentive-compatible systems, such as BitTorrent, our system provides non-manipulable incentives for clients to upload to their peers. A client that honestly uploads to its peers is rewarded in the following two ways. First, if its peers are unable to reciprocate its uploads, the content provider rewards the client's service with credit. This credit can be redeemed for discounts on paid content or other monetary rewards. Second, if the client's peers possess content of interest and have appropriate uplink capacity, the client is rewarded with reciprocal uploads from its peers. In designing Dandelion, we trade scalability for the ability to provide robust incentives for cooperation. The evaluation of our prototype system on PlanetLab demonstrates the viability of our approach. A Dandelion server that runs on commodity hardware with a moderate access link is capable of supporting up to a few thousand clients. The download completion time for these clients is substantially reduced due to the additional upload capacity offered by strongly incentivized uploaders.

In the recent past, anti-P2P companies have successfully curtailed the distribution of targeted content over a number of P2P file-sharing systems, including Kazaa and eDonkey. More recently, anti-P2P companies have begun to attack BitTorrent. In this paper, we analyze the resilience of BitTorrent leechers to two different kinds of attacks: the connection attack and the piece attack. We present the results of both passive and active measurements. Using passive measurements, we performed a detailed analysis of a recent album that is under attack, and identified the behavior of attackers. For our active measurements, we developed a crawler that contacts all the peers in any given swarm, determines whether the swarm is under attack, and identifies the attack peers in the swarm. We used the crawler to analyze 8 top box-office movies. Based on the measurement results, we discovered that BitTorrent architecture is fundamentally resilient to Internet leecher attacks. Finally, we also propose defense mechanisms to further mitigate the attacks and evaluate their effectiveness using trace-driven simulation.

In 3G networks upgraded with high speed packet access (HSPA) technology, the high access bandwidth and advanced mobile devices make it applicable to share large files among mobile users by peer-to-peer applications. To receive files as quickly as possible is essential for mobile users in file sharing applications, since they are subject to unstable signal strength and battery failures. While many researches present peer-to-peer file sharing architectures in mobile environments, few works focus on decreasing the time spent in disseminating files among users. In this paper, we present an efficient peer-to-peer file sharing design for HSPA networks called efficient file sharing (EFS) for 3G networks. EFS can decrease the dissemination time by efficiently utilizing the upstream-bandwidth of mobile nodes. It uses an adaptive rearrangement of a node’s concurrent uploading transfers, which causes the count of the node’s concurrent uploading transfers to lower while ensuring that the node’s upstream-bandwidth can be efficiently utilized. Our simulations show that, EFS achieves much less dissemination time than other protocols including Bullet Prime and a direct implementation of BitTorrent for mobile environments.

Peer-to-Peer (P2P) networks can reduce the distribution cost of large media files for the original provider of the data significantly. Thereby, the BitTorrent protocol is widely used in the Internet today. Most research work studies the protocol analytically, by simulations at the flow-level or real world experiments. For flow-level simulations the influence of neglecting packet-level characteristics (e.g. TCP) is not yet quantified. Therefore, this paper compares packet-level simulation results with flow-level values and analytically derived bounds. Our findings show that BitTorrent is near to optimal at flow-level for different scenarios. Naturally, packet-level results deviate more from the optimal values but differences are at most around 30% in our simulations. Furthermore, we show that the propagation delay can significantly influence the peer selection in BitTorrent and the download performance of the peers. Hence, the unchoking/choking algorithm in BitTorrent exploits implicitly network proximity.

The transfer of large input data files in P2P computing Grids often leads to delays in Task completion times. Existing research related to this topic has been focused on the spatial grouping of Tasks, i.e. reuse of available data through data caching and data-aware scheduling. However, it tends to decrease the level of parallelism of Task execution. In this paper, this issue is addressed by integrating the BitTorrent P2P file sharing protocol, a novel Task selection scheduling algorithm, an existing online, data-aware Resource selection algorithm (similar to Storage Affinity), and caching support. These algorithms have been implemented in the Lightweight Bartering Grid middleware. The Java implementation relies exclusively on Free and Open Source data transfer software (Azureus, Apache FTP server, edtFTPj). The proposed data transfer architecture does not need Predictive Communications Ordering or an explicit deployment of an overlay network. It is also easily deployable. Our main contribution is the joint use of P2P computing and P2P file sharing technologies, enabling a highly scalable and adaptive data transfer architecture to support P2P computing.

Collusive piracy is the main source of intellectual property violations within the boundary of a P2P network. Paid clients (colluders) may illegally share copyrighted content files with unpaid clients (pirates). Such online piracy has hindered the use of open P2P networks for commercial content delivery. We propose a proactive content poisoning scheme to stop colluders and pirates from alleged copyright infringements in P2P file sharing. The basic idea is to detect pirates timely with identity-based signatures and time-stamped tokens. The scheme stops collusive piracy without hurting legitimate P2P clients by targeting poisoning on detected violators, exclusively. We developed a new peer authorization protocol (PAP) to distinguish pirates from legitimate clients. Detected pirates will receive poisoned chunks in their repeated attempts. Pirates are thus severely penalized with no chance to download successfully in tolerable time. Based on simulation results, we find 99.9 percent prevention rate in Gnutella, KaZaA, and Freenet. We achieved 85-98 percent prevention rate on eMule, eDonkey, Morpheus, etc. The scheme is shown less effective in protecting some poison-resilient networks like BitTorrent and Azureus. Our work opens up the low-cost P2P technology for copyrighted content delivery. The advantage lies mainly in minimum delivery cost, higher content availability, and copyright compliance in exploring P2P network resources.

In Peer-to-Peer (P2P) file sharing systems, the presentation of resource attributes organized in different web features can influence users' selection. However, this has been only qualitatively speculated without concrete analysis. In this paper, we conduct extensive quantitative measurements on the impacts of these attributes by crawling web pages of a BitTorrent site, ''5QZone''. The measurement lasts for 31 days, and 168,610 records containing 11,228 distinct resources have been collected. We further compare it with one-day commercial measurement data from a hybrid file sharing site, ''Xunlei'', which contains 5,473,283 resources for 5,156,696 participating users. The finding is twofold. On one hand, it confirms the above qualitative speculation; on the other hand, it shows more significant results: (1) with the highlight feature on popular items, the downloads of each resource yield to a long-tail distribution, deviated from Zipf Law; (2) publications with attracting titles disseminate substantially faster than others; (3) publisher authority feature has limited influence on depressing low quality resources; (4) other features such as presenting resource categories and sizes also affect user behavior. We further demonstrate the implications of the web feature impact for system design and potential attackers.

BitTorrent achives great success in its high performance for file distribution. It is commonly believed that this owes to Tit-for-Tat strategy adopted in choking algorithm for incentive in BitTorrent protocol. But there are still many issues in incentive mechanism in BitTorrent. In this paper, we study Tit-for-Tat strategy by constructing a game model in P2P environments and deducing the constraint under which the strict Tit-for-Tat is an equilibrium strategy. We then enhance and adapt the Tit-for-Tat strategy to the dynamic property in P2P networks, and deduce the constraint under which it is still an equilibrium strategy. We also study through simulations the performance improvement of the enhanced Tit-for-Tat, and give suggestion on how to choose proper system parameters under different network conditions. Finally, based on the enhanced Tit-for-Tat strategy, we propose a method to improve incentive in BitTorrent networks to cope with free-riding and fairness issues.

With the booming of Internet and consumer electronics industry, there are rising amount of content (audio, video, software) that needs to be distributed to increasing number of end consumers in higher speed. Whereas the explosive growth of data-concentrated applications over Internet contributes to the entertainment electronics, the large-scale distribution of huge data to end consumers with guarantee of Quality of Service (QoS), remains an elusive goal. The potential integration of Peer-to-Peer (P2P) paradigm into the Internet content distribution infrastructure provides a disruptive market opportunity to scale the Internet for higher quality data delivery. While the theoretical benefits of P2P in regular Internet has been widely reported, it remains unknown on its performance for large-scale mass data delivery over high-speed networks, highly promising yet controversial. This paper thus provides an experimental and analytical performance study over BitTorrent-like P2P networks for accelerating large-scale content distribution over booming Internet. Our study explores the unique strength of P2P in high speed networks, identifies performance bottlenecks, and quantifies the special requirements in the new scenario, i.e. file piece length and seed capacity. Further, to enable services before full downloading, this paper proposes a Piece-On-Demand (POD) scheme to modify BitTorrent in integration with Filesystem in Userspace (FUSE) to both decrease file distribution time and increase service availability. To demonstrate the feasibility of adopting P2P as a reliable consumer network for content distribution, we further illustrate our industrial exploration on utilizing P2P in deployment for application/services with huge image, providing unprecedented deployment speed and scalability for enabling on-demand services to large-scale users.

The BitTorrent (BT) file sharing protocol is very popular due to its scalability property and the built-in incentive mechanism to reduce free-riding. However, in designing such P2P file sharing protocols, there is a fundamental trade-off between keeping fairness and providing good performance. In particular, the system can either keep peers (especially those resourceful ones) in the system for as long as possible so as to help the system to achieve better performance, or allow more resourceful peers to finish their download as quickly as possible so as to achieve fairness. The current BT protocol represents only one possible implementation in this whole design space. The objective of this paper is to characterize the design space of BT-like protocols. The rationale for considering fairness in the P2P file sharing context is to use it as a measure of willingness to provide service. We show that there is a wide range of design choices, ranging from optimizing the performance of file download time, to optimizing the overall fairness measure. More importantly, we show that there is a simple and easily implementable design knob so that the system can operate at a particular point in the design space. We also discuss different algorithms, ranging from centralized to distributed, in realizing the design knob. Performance evaluations are carried out, both via simulation and network measurement, to quantify the merits and properties of the BT-like file sharing protocols.