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In order to guarantee the downloading quality requirements of users and improve the stability of data transmission in a BitTorrent-like peer-to-peer file sharing system, this article deals with eigenproblems of addition-min algebras. First, it provides a sufficient and necessary condition for a vector being an eigenvector of a given matrix, and then presents an algorithm for finding all the eigenvalues and eigenvectors of a given matrix. It further proposes a sufficient and necessary condition for a vector being a constrained eigenvector of a given matrix and supplies an algorithm for computing all the constrained eigenvectors and eigenvalues of a given matrix. This article finally discusses the supereigenproblem of a given matrix and presents an algorithm for obtaining the maximum constrained supereigenvalue and depicting the feasible region of all the constrained supereigenvectors for a given matrix. It also gives some examples for illustrating the algorithms, respectively. [ABSTRACT FROM AUTHOR]

This study examines the relationship between interest rate and defunct platform risk of China's peer-to-peer (P2P) lending platforms. P2P lending provides an alternative funding source for individuals and micro-enterprises and offers a new investment tool for households. But the frequent collapses of many platforms were huge losses to market participants and even led to a decline in China's P2P lending industry. In this study, weekly data of 76 platforms from December 3, 2017, to October 6, 2019, are employed, and empirical research based on the normal and skew-normal panel data model respectively is conducted. Statistical indicators prove that the skew-normal panel data model is preferable to another one in modeling the data set of interest rates. The empirical results show that China's P2P market is efficient overall. But the positive correlation between the interest rate and risk is not significant for platforms with excessively high interest rates, whose interest rates are more determined by the types of ownership. The findings and implications are provided in the end. [ABSTRACT FROM AUTHOR]

Construction projects' performance is not self-regulating. Therefore, a continuous progress tracking and monitoring process is highly demanded to avoid potential deviations or misalignments. The current practice for the progress tracking and monitoring process suffers from heavily intermediated workflows, human errors, transfer latencies, inaccuracies, and/or information holes. Such issues could gradually lead to severe delays or even complete project failure. This research introduces a novel Peer-to-Peer (P2P) system that relies on Blockchain Technology (BT) and Inter-Planetary File System (IPFS) for managing progress information and as-built digital assets or files. The system is developed based on a three-step approach. First, two chaincodes are formulated for mapping and governing the data operations. Second, a private blockchain network is configured based on Hyperledger Fabric as a hosting platform, including the relevant stakeholders. Third, a private IPFS network is configured and coupled with a cluster service to manage and distribute the off-chain visuals and as-built digital assets. A case study for a non-residential construction project is utilized to test and verify the system's practicability and assess its performance. The research significance is anticipated in diverse practical areas, including but not limited to; boosting coordination and trust among stakeholders, tracing progressive elaboration of As-built digital assets, accelerating incremental payments processing, assessing overall project performance and on-site productivity, supporting delay analysis and claim/dispute management, and streamlining data flow between the construction phase and the operation and maintenance phase. Further, the system's future is mapped by evolving it as a sub-unit in a more advanced data model. [ABSTRACT FROM AUTHOR]

Blockchain is often compared to the internet as a disruptive technology that will realign economic structures across the world. This analogy extends to law and regulation. Similar to internet-based services, digital assets raise a host of challenges for policymakers. They also pose general questions regarding the desirability and practicality of regulating decentralized systems. Such debates play out against a backdrop of concerns that regulatory action will chill innovation or push market activity to more tolerant jurisdictions. The story of internet policy in the late 1990s and early 2000s therefore provides important lessons for policymakers today when confronting digital assets. Two incidents are of particular significance: the Clinton administration’s 1997 Framework for Global Electronic Commerce and the judicial effort to address peer-to-peer (P2P) file sharing. The early internet regulatory debates demonstrated that action by all three branches of government was important to resolve uncertainties and distinguish legitimate from illegitimate market activity. The history illustrates that policymakers have many tools at their disposal beyond direct prohibitions or exclusions from requirements. Claims that regulation is inherently impossible or damaging to market development are generally overblown. Focusing on policy objectives, rather than starting from traditional categories that were historically developed based on those objectives, will help policymakers develop appropriate rules for novel digital asset markets such as decentralized finance (DeFi). [ABSTRACT FROM AUTHOR]

We are currently witnessing a global increase in the provision of software platforms and services, offered at «no cost» by large corporations, to higher education. The business model behind these services is largely based on the collection and analysis of massive quantities of user data and metadata, collected through educational packages, which include e-mail, videoconferencing, groupware, file sharing, and other integrated services. The penetration of these services in higher education worldwide is largely unknown. In this study we discuss a methodology and a software script developed to collected new data for all 448 public higher education institutions in all 13 countries in South America. The data show that for every ten higher education institutions in the region, eight have services and platforms offered by such businesses. We contend that the adoption of these services is largely due to disinvestment in public education, and threaten the operational autonomy of institutions in regards to research and teaching, while leading to concerns in regards to data control, privacy, and transparency for teachers, administrators and students. [ABSTRACT FROM AUTHOR]

Peer-to-Peer (P2P) networks is a distributed structure, which is widely used in file sharing, distributed computing, deep search engines. Each node plays the dual role of client and server, which makes the P2P network further exacerbates the insecurity of P2P systems. For the behavior of nodes in P2P systems, requesting nodes are abstracted into customers and service nodes are abstracted into servers. An M/M/c queueing model is developed with dynamically changing servers in almost unobservable cases, strategies are introduced, including start-up period, working sleep of service nodes and negative customers, etc. Using the matrix-geometric solution and Gauss-Seidel iteration method, average waiting length, average sojourn time, total energy consumption and throughput are derived. Through numerical experiments, the process of P2P file sharing is simulated, the optimal value of social utility is obtained using Nash equilibrium and social optimal strategy, and a theoretical basis is provided for node scheduling in P2P systems. [ABSTRACT FROM AUTHOR]

Peer-to-peer sharing has become increasingly popular in recent years. Many digital platforms exist that allow individuals to use others' belongings part-time. These platforms explicitly mention their green credentials, as the environmental benefits of such sharing initiatives are often taken for granted. However, there is a recent empirical literature showing evidence of the contrary. We propose a theoretical framework to analyze the economic and environmental implications of peer-to-peer sharing. We present a stylized model where a monopolist supplies a product that is suitable for rent on a sharing platform. Interestingly, we find that the existence of such a platform is typically beneficial for the monopolist, especially in the long run, when she can optimally anticipate the effects of her decisions on the sharing market. Such a scenario may not be beneficial for consumers, especially for those who rent the good rather than buy it. Moreover, the existence of the sharing platform induces higher use and (under some likely conditions) larger production levels and shorter product lifespans. The combination of these three aspects contributes to a worse environmental impact with sharing, which provides a theoretical rationale for the aforementioned empirical studies. [ABSTRACT FROM AUTHOR]

With the increasing number of fibre access users, P2P file sharing download traffic has gradually become one of the enormous bandwidth consumptions for the access network. Localizing traffic could save bandwidth and reduce latency, but it caused optical line terminal (OLT) overload problems. A cloud‐edge collaboration technology (IRS‐CECT) based P2P redirection strategy is proposed for this problem. OLT assumes the role of the cloud computing centre in the strategy. Optical network unit (ONU) serves as an edge computing node to share traffic load for the cloud computing centre. ONU intercepts the upstream query packets for OLT. This strategy can reduce the problem of OLT overload caused by increasing users. Simulation results indicate that the IRS‐CECT strategy can reduce the delay by nearly half and reduce the traffic load on the cloud computing centre OLT. [ABSTRACT FROM AUTHOR]

The article discusses a research study conducted to unravel the reasons piracy thrives in the Nigerian environment in the face of a virile copyright law meant to protect the rights of copyright holders, punish infringers and defaulters of the law. It also analyzes factors responsible for the high level of piracy in Nigeria. Due to technological advancement, the Piracy business has become sophisticated and global in nature and scope.

Transgender peer-to-peer support groups can provide an invaluable space for healing by fostering collective knowledge, resource sharing, and supportive self-determination. Historically, transgender people have facilitated these grassroots mental health and gender transition supports within their communities, picking up the slack where providers and healthcare systems have either fallen short, or worse, have actively sought to bar access. Peer models emerge from these community-based movements but have also started to become more formally integrated into some state-funded models of healthcare. The following article investigates the impacts of clinical work conducted in institutionally funded, peer-to-peer transgender mental health support groups through a narrative-driven conversation between the authors: a transgender service provider and a transgender service user. Drawing on our shared experience, we discuss the benefits and shortcomings of this innovative, yet delegitimized form of healthcare provision for transgender people. [ABSTRACT FROM AUTHOR]

Peer-to-peer streaming has emerged via software developed for swapping and sharing digital content (such as music, films, TV shows and live sports) with others across the internet. Peer-to-peer streaming has become an expedient technique for end-users, because it allows access to digital content without downloading it. However, while it is a novel advancement in technology, peer-to-peer streaming has heralded new challenges for copyright-protected works. This is because peer-to-peer streaming can affect the right of communication to the public, which is the exclusive right of the copyright owners. The process of making digital content available for others through peer-to-peer streaming can result in copyright-protected work being distributed illegally. This paper examines whether peer-to-peer streaming infringes the right of communication to the public in Australia. [ABSTRACT FROM AUTHOR]

Considering the requirement of the biggest download speed, a Peer-to-Peer (P2P) file sharing system can be reduced into a system of max–min fuzzy relation inequalities. In order to decrease the network congestion under some fixed priority grade of the terminals, fuzzy relation lexicographic programming is proposed to model the P2P file sharing system. For solving the proposed problem, we define concept of feasible index set and discuss some simple properties. Based on the feasible index set, a novel algorithm is developed to find the optimal solution with an illustrative example. [ABSTRACT FROM AUTHOR]

Abstract Contemporary e-commerce platforms enable the exchange of idle resources among private individuals directly from peer to peer. The success of peer-to-peer sharing platforms largely depends on the capability of platform providers to understand the users' motives for engagement. To investigate the relative importance of consumer motives for and against peer-to-peer sharing, we develop a theoretical model based on a comprehensive set of potential consumer motives. We validate our model by means of a survey among 745 participants. Our findings suggest financial benefits, trust in other users, modern lifestyle, effort expectancy, and ecological sustainability as the five most important drivers and prerequisites of platform usage intentions. Based on our findings, we suggest directions for future research on peer-based sharing and discuss implications for both theory and practice. Highlights • Overview of user motives for taking part or evading peer-to-peer sharing (PPS). • Development of a corresponding survey-based measurement model. • Identification of the strongest motives for and against PPS usage intentions. • (+) Financial benefits, trust in other users, and modern lifestyle. • (−) Effort expectancy, independence through ownership, and process risk concerns. [ABSTRACT FROM AUTHOR]

• Worm spreading in P2P network is studied using a graph-based model. • Trust management systems are introduced in order to mitigate worm spreading. • We consider a hybrid system where we hybridize file-based and peer-based trust models. • We found that the hybrid trust models could mitigate more efficiently the worm propagation in the P2P networks. • We found also that FileEigen Trust system (A hybrid between FileTrust and EigenTrust) is the most efficient one for mitigating worms in P2P networks. Passive worms spread so quickly in P2P networks that they can cause significant damage and serious security problems. To mitigate worm spreading, we used two classes of trust models: file-based trust and peer-based trust models. Peer-based trust provides to a peer the global trust values of all the other peers using the peers history of uploads. File trust provides to a peer the trust level of its sought file thanks to a process of voting. An hybrid trust model is introduced where we hybridize file-based and peer-based trust models. In this hybrid trust model, a requester peer checks firstly on the safety of the sought file (file trust) and then choose the most reputed peer from the set of peers that own the file (peer-based trust) for the downloading. A detailed simulation analysis is performed to study the performance of these trust models in terms of fraction of infected peers and number of infected downloaded files. Our results show that peer-based trusts could be used to mitigate the spread of worms in P2P networks because they limit downloading from malicious peers; but they are not effective in reducing the download rate of infected files from normal peers. Furthermore, we find that hybrid trust is an adequate security solution for mitigation of worm spreading in P2P network. Moreover, with comparison of several examples of peer-based trusts, we show that if we hybridize any peer-based trust with file trust, we obtain that the hybrid model is more efficient than this peer-based trust. [ABSTRACT FROM AUTHOR]

Internet-mediated sharing is growing quickly. Millions of users around the world share personal services and possessions with others ‒ often complete strangers. Shared goods can amount to substantial financial and immaterial value. Despite this, little research has investigated privacy in the sharing economy. To fill this gap, we examine the sharing-privacy nexus by exploring the privacy threats associated with Internet-mediated sharing. Given the popularity of sharing services, users seem quite willing to share goods and services despite the compounded informational and physical privacy threats associated with such sharing. We develop and test a framework for analyzing the effect of privacy concerns on sharing that considers institutional and social privacy threats, trust and social-hedonic as well as monetary motives. [ABSTRACT FROM AUTHOR]

In the last years peer-to-peer (P2P) networks have become an important and prevalent architecture in the Internet and have been commonly applied into many scenarios such as big data storage and management, cloud computing, vehicular networks and social networking. The overall performance of P2P networks mainly depends on cooperation between peers, so as to encourage each peer to contribute its resource to others and reduce free-riding behaviors. Then each peer has to face a dilemma decision that how much of its available bandwidth it will allocate to uploads for others and how much it will reserve for its own downloads. In this paper we consider bandwidth allocation in P2P networks where both upstream and downstream flows traverse one common access link with finite capacity, and formulate the utility maximization model for bandwidth allocation. The model is difficult to resolve since it is an interplay problem between upload and download decisions of each peer. In order to achieve the optimal bandwidth allocation, we present a heuristic scheme using Particle Swarm Optimization (PSO), and discuss the performance with numerical examples in different network scenarios. Simulation results show that the scheme can achieve the global optimum within reasonable iterations. [ABSTRACT FROM AUTHOR]

Academic libraries are providing technical support and assistance to their patrons using models such as the information commons, learning commons, and designated service points. Applying a constructivist, experiential approach, one small liberal arts college created a team of students to provide peer-to-peer tech support in response to an influx of new technology resources and equipment available for checkout. This team has provided much-needed services to the campus and an important professional development opportunity for its members. This experience offers a useful example for implementing in-house technical support in libraries at similar institutions. [ABSTRACT FROM AUTHOR]

This article re‐examines what constitutes genuine sharing in peer‐to‐peer collaborative transactions by contrasting a pet owner‐borrower matching initiative to other enterprises such as Uber and Airbnb. It argues that aims of public spiritedness and community building through interactions are essential for sustaining peer‐to‐peer collaborations. When money is the focal point of exchange, the collaborative relationship is motivated by profit making rather than goals of sustainability, well‐being or good citizenship. Interactions that create new kinds of connections within communities (rather than replacing traditional connections with cheaper or more accessible ones) are more likely to generate a genuine sharing ethos. The chief implication of the case study is that collaborators need to think carefully about objectives and means of exchange. Capturing new kinds of productive relationships, which are not overly reliant on the exchange of money, may contribute to genuine exchange and enhance community relations, leading to greater cultural citizenship. [ABSTRACT FROM AUTHOR]

Sustainable business models are intended to create economic value while benefitting the environment and society. Their wider adoption and diffusion is necessary to tackle pressing societal problems. How they are implemented and what determines their success (or lack thereof) in the market is not yet well understood, however, and deserves further exploration. To help fill the gap in knowledge, this study examines an emerging and innovative type of sustainable business model based on the peer-to-peer (P2P) sharing of underutilised assets facilitated by digital platforms. Its aim is to identify possible reasons for their commercial success or failure. In particular, the study investigates the values of users of a successful P2P goods-sharing platform and to what extent they differ from values of users of a comparable, yet unsuccessful, platform. Previous research on a UK-based online marketplace, Ecomodo, measured people's motivations for joining and the value priorities of users using Schwartz's Portrait Value Questionnaire. Results were compared with data from a representative sample of the UK population and used to explain the platform's low market uptake. The same study is here replicated with members of Peerby, an online marketplace where people rent, lend and borrow their possessions with each other. The analysis shows similar value priorities and orientation in Ecomodo and Peerby respondents, which suggests that the failure of the former platform and the success of the latter may be more directly attributed to differences in their business model design and execution than the types of user. [ABSTRACT FROM AUTHOR]

A learning rule is completely uncoupled if each player's behavior is conditioned only on his own realized payoffs, and does not need to know the actions or payoffs of anyone else. We demonstrate a simple, completely uncoupled learning rule such that, in any finite normal form game with generic payoffs, the players' realized strategies implements a socially optimal coarse correlated (Hannan) equilibrium a very high proportion of the time. That is, the empirical frequency associated with the players' collective behavior will be consistent with a socially optimal coarse correlated equilibrium. A variant of the rule implements a socially optimal correlated equilibrium a very high proportion of the time. [ABSTRACT FROM AUTHOR]

Device-to-device (D2D) communications are not only featured by high spectral and energy efficiency, but also offer appealing benefits for applications, such as message dissemination, traffic offloading, and coverage expansion. In this paper, we consider a message dissemination scenario where a base station (BS) can direct message requests to be fulfilled by some source devices via D2D communications and thereby save the resource cost. Furthermore, a source device may be subject to a cost budget due to its limited resources. To minimize the overall cost or maximize the BS's cost saving from offloading, it is essential to properly assign the message request(s) for each source and decide the payment to incentivize participation. The request direction is an NP-hard problem, while the payment determination is also nontrivial. The payment should be sufficient to compensate for a source device's resource cost, and meanwhile, incentivize the source to truthfully declare its private cost and budget. Modeling the problem as a reverse auction, we develop both a deterministic mechanism and a randomized mechanism, which are truthful or truthful in expectation, respectively. Both mechanisms are individually rational and subject to a computational complexity lower than that of the well-known Vickrey–Clarke–Groves mechanism or its generalized version. While the deterministic mechanism performs well in an average sense, the randomized mechanism maintains an approximation guarantee for the worst case. Extensive numerical results demonstrate the effectiveness of the proposed mechanisms with various settings in the D2D content distribution scenario. [ABSTRACT FROM PUBLISHER]

This communication presents the results of the first field measurement campaign to characterize the large- and small-scale propagation statistics of the peer-to-peer wireless link in an operating petroleum refinery. Results for ground level transmission and transmission between ground level and devices mounted 18 m from the ground on a distillation stack are included. The measurements characterize the 20-MHz $2 \times 1$ multiple-input, single-output channel at 2.45 GHz. Analysis of the measurement data reveals an environment with severe small-scale fading and multipath dispersion but very mild large-scale signal attenuation given the level of obstruction on the links. [ABSTRACT FROM PUBLISHER]

In BitTorrent network, the bitmap is used to indicate the state of data blocks of file owned by a peer. Before the downloading of the file starts, the file provider first sends its corresponding bitmap to the requester to show which data blocks it owns. This provides the possibility for hiding the identity information in the bitmap and exchanging the identity information secretly. In this paper, we propose a bitmap-based steganographic handshake approach and implement a prototype system based on the BitTorrent network. In our prototype system, the network can operate normally. More importantly, hidden peers successfully exchange their identity information and accurately identify the other hidden peers without being detected by the regular peers. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

Peer-to-peer video on demand (P2P-VoD) is a solution to provide video service to a large number of users on the Internet. Due to the upload bandwidth bottleneck of VoD servers, the streaming capacity in the P2P-VoD system is limited. This paper proposes a new mechanism to improve the video streaming in P2P networks by using the idle peers upload bandwidth and storage, which are called helpers. The proposed method uses an XOR mechanism in the VoD server to encode chunks and reduce bandwidth use. The helpers receive encoded chunks from the VoD server and save them in their storage spaces and cooperate in sharing these chunks with the other peers. Simulation results using OMNET++ are provided to show the efficiency of the proposed mechanism in terms of the required upload capacity requirement of the server and deploying the storage and bandwidth of helpers. The results of simulation show that the upload bandwidth usage of the server has been reduced. On the other hand, the proposed method increases the memory usage of helpers. [ABSTRACT FROM AUTHOR]

Due to the loosely coupled property of cloud computing environments, no node has complete knowledge of the system. For this reason, detecting a Sybil attack in cloud computing environments is a non-trivial task. In such a dynamic system, the use of algorithms based on tree or ring structures for collecting the global state of the system has unfortunate downsides, that is, the structure should be re-constructed in the presence of node joining and leaving. In this paper, we propose an unstructured Sybil attack detection algorithm in cloud computing environments. Our proposed algorithm uses one-to-one communication primitives rather than broadcast primitives and, therefore, the message complexity can be reduced. In our algorithmic design, attacker nodes forging multiple identities are effectively detected by normal nodes with the fail-stop signature scheme. We show that, regardless of the number of attacker nodes, our Sybil attack detection algorithm is able to reach consensus. [ABSTRACT FROM AUTHOR]

Crowdsourced research sharing takes place across social media platforms including Twitter hashtags such as #icanhazpdf, Reddit Scholar, and Facebook. This study surveys users of these peer-to-peer exchanges on demographic information, frequency of use, and their motivations in both providing and obtaining scholarly information on these platforms. Respondents also provided their perspectives on the database terms of service and/or copyright violations in these exchanges. Findings indicate that the motivations of this community are utilitarian or ideological in nature, similar to other peer-to-peer file sharing online. Implications for library services including instruction, outreach, and interlibrary loan are discussed. [ABSTRACT FROM AUTHOR]

The article focuses on music creation and consumption as a starting point to consider underlying dominant assumptions about musical practice and the implications of actual processes of music perception and cognition. It mentions displacement has significant implications for assumptions about musical copyright with attribute to piracy or peer-to-peer (P2P) file sharing. It also mentions dissemination of digital music with increased focus on copyright law.

The article focuses on the role that regulatory bodies in the European Union and the U.S. are playing in making data sharing a compulsory resultant of the marketing approval process. Topics discussed include evolution of data sharing regimes; evaluation of justifications for increased sharing; and the distribution of risk in the data sharing systems.

The article focuses on management of intellectual property legislation with evolution of Internet services. Topics include development of broadcast data firm Outernet for provision of Internet accession services, establishment of the firm by the Media Development Investment Fund (MDIF), dependence of the firm with User Datagram Protocol (UDP) multitasking services, concerns regarding intellectual protection with initiation of peer-to-peer sharing and management of infringement concerns.

The article examines the laws related to electronic possession of child pornography in the U.S. Topics discussed include enforceability of child pornography laws; increasing peer-to-peer (P2P) file-sharing and online streaming worldwide; challenges to criminalization of child pornography; and need of a proper paradigmatic tool for analyzing the electronic possession of child pornography.

The Peer-to-Peer (P2P) architecture has been successfully used to reduce costs and increase the scalability of Internet live streaming systems. However, the effectiveness of these applications depends largely on user (peer) cooperation. In this article we use data collected from SopCast, a popular P2P live application, to show that there is high correlation between peer centrality-out-degree, out-closeness, and betweenness-in the P2P overlay graph and peer cooperation. We use this finding to propose a new regression-based model to predict peer cooperation from its past centrality. Our model takes only peer out-degrees as input, as out-degree has the strongest correlation with peer cooperation. Our evaluation shows that our model has good accuracy and does not need to be trained too often (e.g., once each 16 min). We also use our model to sketch a mechanism to detect malicious peers that report artificially inflated cooperation aiming at, for example, receiving better quality of service. [ABSTRACT FROM AUTHOR]

Incentive schemes are designed to promote cooperation in distributed systems, in which peers are free to decide how much to contribute. A variety of incentive schemes have been proposed in peer-to-peer file-sharing systems, touted to have special advantages in certain scenarios. However, only little research has been done on comparing these incentive schemes under an identical scenario. Fairness is an important indicator to evaluate an incentive scheme, because good fairness can enable proper rewarding to collaborative peers and punishment to strategic peers. In this paper, the correlation map between return and investment of peers is used to depict the fairness degree of different incentive schemes. The fairness and efficiency of several representative incentive schemes are compared under rate-based metrics (all chunks have an identical value) and value-based metrics (different chunks have different values). [ABSTRACT FROM AUTHOR]

This text is a summary of my dissertation where I try to show some key points of the study. I chose to discuss very concisely the motivations that have led me to conduct the study in Bulgaria but also my methodological inspiration and the fieldwork I have done. Here, I also introduce the three main actors in the network of relations, constructed as a result of the ethnographic study: Internet Providers, Torrents Trackers and Subtitling pages. [ABSTRACT FROM AUTHOR]

A network coding based peer-to-peer (P2P) file sharing system has been proposed in recent years. It uses the random combination of encoded pieces to make the file sharing more effective. Most of the conventional P2P file sharing systems adopt a random (or rarest piece first) transmission policy to avoid too many duplicated pieces and rare pieces occurring in the network. Network coding can simply solve this problem. However, some of the studies show that network coding brings the overhead of coding/decoding delay and message overhead; after all, the performance of network coding is not better than other schemes that are without network coding. Therefore, we propose a network coding based file sharing system over unstructured P2P networks considering the overhead from the network coding. We make comparisons with other schemes without network coding. Our simulation results show that the proposed network coding based file sharing system is better than others, when the network coding scheme and non-network coding scheme adopt the same network environment even though the network coding is executed under a limited computation resource. [ABSTRACT FROM AUTHOR]