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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]

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]

Encryption methods had been widely used for secure data transmission and communication in both public and private organizations against intruders. Rivest-shamir-adleman (RSA) encryption algorithm is one of the most popular and efficient encryption schemes that has been in used for decades. Due to technological advancement and innovation, there is a threat to this algorithm. It is believed that introduction of quantum computer will break RSA algorithm easily. In view of this, it is pertinent to research into how RSA algorithm could be strengthened against all adversaries. This research aim at protecting client/server communication and file sharing by generating dynamic public and private keys. The proposed method was implemented in visual basic.net 2008. The result shows that dynamic keys do not affect the performance of the system and it is capable of protecting communication and file sharing between client/server. As the key generated keeps changing at an interval, it will difficult for most advance computer to factor any of the keys before another key is generated. This is the basis of the security of the proposed system. [ABSTRACT FROM AUTHOR]

In this paper, we study a new type of fuzzy relation system called fuzzy relational inequalities with addition-min-product composition operations to model a peer-to-peer (P2P) file sharing system. Some properties of this addition-min-product system are investigated. We then characterize the structure of the solution set. Furthermore, to reduce the network congestion and improve the stability of data transmission, a min–max programming problem with constraints of addition-min-product fuzzy relation inequalities is established and investigated. We divide this min–max programming problem into several subproblems with the constraint of a single equation. Based on the optimal solutions to these subproblems, we can solve the original fuzzy relation min–max programming problem. Two algorithms, with polynomial computational complexity, are developed to search for an optimal solution to our studied problem. The validity of the algorithms is examined through a numerical example. [ABSTRACT FROM AUTHOR]

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]

In this paper, we study an optimization problem of minimizing a linear function subject to fuzzy relational inequalities with the addition–min composition. This optimization setting has recently been proposed to model the network cogestion issue when a BitTorrent-like peer-to-peer file-sharing system is used for data transmission. In a 2014 paper, a pseudominimal index (PMI)-based approach was proposed to search for an optimal solution. It turns out that the PMI-based approach may require to solve several to many linear programming problems in order to get an optimal solution. In this paper, we point out that the feasible domain is indeed convex. And we only need to solve a single linear programming problem to generate an optimal solution for the original optimization problem. Furthermore, our approach could be extended to the case with a nonlinear continuous objective function. [ABSTRACT FROM PUBLISHER]

In peer-to-peer (P2P) file sharing networks, it is common practice to manage each peer using reputation systems. A reputation system systematically tracks the reputation of each peer and punishes peers for malicious behaviors (like uploading bad file, or virus, etc). However, current reputation systems could hurt the normal peers, since they might occasionally make mistakes. Therefore, in this paper, we introduce forgiveness mechanism into the EigenTrust reputation system to reduce such malicious treatments and give them opportunities to gain reputation back. Particularly, we take four motivations (the severity of current offence, the frequency of offences, the compensation and the reciprocity of the offender) into consideration to measure forgiveness. The simulation work shows that the forgiveness model can repair the direct trust breakdown caused by unintentional mistakes and lead to less invalid downloads, which improves the performance of P2P file sharing systems. [ABSTRACT FROM AUTHOR]

Reputation systems have been proposed to distinguish malicious peers and ensure the quality of services in P2P networks. How-ever, only relying on global reputation scores to assess the reliability of file providers can weaken the subjective opinions of file requesters, which is vulnerable to some malicious attacks, e.g., camouflage attack. To address this issue, in this paper, we propose a novel hybrid trust model, namely HTM, based on the EigenTrust reputation management system. In HTM, a file requester utilizes a two-phase reference method to take both the global reputation and the direct trust of a file provider into consideration when deciding whether to download from it or not. In particular, in the first phase, a requester selects a provider from the responders based on the roulette wheel selection algorithm; while in the second phase, the requester considers the direct trust on the selected provider with our proposed direct trust evaluation approach. The extended simulation results show that our mechanism can identify and isolate the malicious peers both under individual attack and camouflage attack effectively, thus improving the performance of P2P file sharing networks. [ABSTRACT FROM AUTHOR]

There is a significant growth of the peer-to-peer (P2P) systems over the last few years because of their high potential for sharing file among the peers. Selection of the optimal peer ensures high data transmission rate and reduced network cost. However, it is highly difficult to select the optimal peer because of the variation in the heterogeneous capacity and dynamic capacity of the peers. Efficient peer selection approach is highly required to overcome this difficulty. This paper proposes a particle swarm optimization (PSO)-based optimal peer selection approach for a highly secure and trusted P2P system, based on the bandwidth and trust level of the peers. File replication is performed to effectively tackle the overloading of the hot files. Replacement of the replicated file is performed, based on their demand rates. The success rate and bandwidth rate of the peer are computed. Bandwidth and trust-based PSO is applied to select the optimal peer. This improves the success rate for the peer transmission. After selecting the optimal peer, the replicated file is encrypted and transmitted to the selected peer. Finally, the replicated file is decrypted. Our proposed approach achieves minimum average query delay and ensures a highly secure and trusted environment for the P2P systems. The performance of the proposed approach is evaluated by comparing the proposed approach with the existing techniques. From the comparison results, it is clearly evident that the proposed approach achieves higher success rate and lower link stress, delay, communication overhead, finished time and network cost. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The state of art authentication schemes are tightly linked with encryption or crypto systems, which provides concrete foundations to move towards the concept of access control by confirming the user identity. However the openness of the computer network makes the identity credentials vulnerable even transmitted as cipher text especially in lots of peer-to-peer (P2P) networks. The malicious attackers can possibly steal and fake the user identity by eavesdropping, hijacking, cryptanalysis and forging. In this paper, a novel identity authentication mechanism is proposed based on the reverse usage of the Network Covert Channel (NCC) which is originally designed by attackers to create stealth communication. Different from NCC, where the packet intervals can be exploited as the data carrier to transmit the unauthorized information, we exploit such capability in Network-Covert-Channel-based Identity Authentication (NCCIA) to transmit the identity tag. By validating user identity in a covert manner, we provide a more secure authentication method compared with many existing approaches. A NCCIA demo system is designed on a FTP Platform to verify our method. The experiments demonstrate the NCCIA can prevent the attackers from eavesdropping while maintaining transmission efficiency. [ABSTRACT FROM AUTHOR]

Peer-to-Peer (P2P) technology has experienced its great popularity for resource sharing in current network services. However, lacking of prior experience and knowledge about other peers' reputation, P2P suffer from malicious behaviors launched by malicious peers. Developing effective strategies to establish trust model for the P2P system is a good way to address this problem. In this paper, we propose a novel topological potential weighted community-based recommendation trust (TPCommuTrust) model architecture, which is based on topological potential weighted community credential to score and rate peers' previous data transactions. Contributed by topological potential, which characterizes repercussion effect between peers, the reputation model of the peers is created. The unique and efficient mechanism is proposed to perform data transaction based on credentials intra and inter-community. Moreover, how TPCommuTrust can provide an access control against malicious peers is illustrated as well. Simulation results show that TPCommuTrust model is robust and highly efficient to identify malicious nodes. [ABSTRACT FROM AUTHOR]

Peer-to-peer relay technique provides the opportunity of cooperative communication between users to achieve the transmission diversity. In this paper, the problem of relay selection and subcarrier allocation in peer-to-peer cooperative OFDMA system with channel distribution uncertainty is studied. The quality of service (QoS) requirements are characterized with the probabilistic constraints. The Kullback-Leibler (KL) divergence is adopted to describe the uncertainty of the channel state information (CSI), which follows a distribution deviated within a certain distance from the reference distribution. Since the probabilistic constraint is intractable, we resort to a tractable upper bound instead. The problem is solved by the interior point cutting plane (IPCP) method, which proceeds in round whereby an iterative method is designed to combine both golden section method and interior point method to find the saddle point of the constraint. Simulation results show the effectiveness of our algorithm. [ABSTRACT FROM AUTHOR]

Private BitTorrent community, known as 'BitTorrent Darknet' or 'Private Tracker (PT)', has received much attention in the research literature recently. Different from public BitTorrent community, PT can only be accessed by its registered members, and it can provide ultra-high downloading speed due to its effective Sharing Ratio Enforcement (SRE) incentive mechanism which stimulates members to contribute content as much as possible. Although the downloading performance in PTs with high Seeder-to-Leecher Ratio (SLR) is much better than in public BitTorrent communities, our measurements show that SRE mechanism can induce 'Poor Downloading Motivation' problem for members who want to increase their sharing ratios to survive and thrive in PT. This problem may discourage PT members' enthusiasm from contributing to community. To improve sustainability of PTs, we adopt the Predator-prey model to analyze high SLR phenomenon, study the optimal stable SLR range to PTs. Moreover, we develop a queuing model to simulate the seeding/leeching process in a single torrent in PT, and try to maximize the swarming performance with minimum seeding peers. This solution can help PT achieve the optimal SLR range. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a trust model based on real-time behavior detection scheme was proposed in P2P file-sharing system. It solved the problems in computing trust value only by past performances and choosing service nodes improperly. It took real-time behavior detection both in trust computing and service choosing, improving the accuracy of the trust value and the rationality in service nodes choosing. The experimental results proved the advantage of this scheme. [Copyright &y& Elsevier]

This paper examines recent responses by U.S. university administrators to the volume and legal challenges surrounding on-campus and in-residence peer-to-peer (P2P) traffic. Since the earliest days of online P2P activity, universities have served as key flashpoints in the broader file sharing and intellectual property debates. But while there has been considerable attention to the emerging file-sharing case law, and some attention to the shifting legal and political strategies of IP holders most affected by P2P traffic (or most aggressive in asserting their rights), the multiple, varied, and often ambivalent responses of university network administrators have for the most part escaped sustained attention. This paper draws on published survey and original interview data to explore the distinctive and heterogeneous policy sets put together by campus network administrators and decision-makers in dealing with IP issues associated with on-campus file-sharing practice. Such institutional micro-regimes constitute a crucial and understudied border zone between law and culture, functioning as key translation points through which external IP claims get filtered (e.g., DMCA take-down notices), and strategic sites at which a substantial amount of real-world IP regulation is effectively accomplished. [ABSTRACT FROM AUTHOR]

To investigate the factors that affect incentive mechanism of BitTorrent system, this paper makes a modeling analysis. Because there are random selections, we use Markov process to model the incentive mechanism. We first get the transition probability matrix and then calculate the limit of the transition probability matrix. Theoretical analysis and experiment results show that peers with same upload bandwidth cluster, and adjusting randomly selected nodes can affect the speed of clustering. The model is consistent with the incentive mechanism, and by adjusting parameters we can improve the performance of the system. [ABSTRACT FROM AUTHOR]

The article highlights the legal issues that have evolved since the creation of the fourth generation peer-to-peer (4G P2P) Internet file transmission technology particularly in the copyright era. It explores the similar characteristics between the method of file transmission and traditional broadcasting. The importance of studying the technology together with defining rights of the author over the 4G P2P is explained.

Abstract: In large-scale peer-to-peer (P2P) computing, trust management technology has become a key requirement for network security. However, trust is one of the most complex concepts in network communities. It involves many factors, such as, assumptions, expectations, behaviors, risks, and so on. As a result, trustworthiness has multi-dimensional properties. In this paper, an innovative trust model is proposed for large-scale P2P computing, in which multiple factors are incorporated to reflect the complexity of trust. More importantly, the properties (weights) of these factors are dynamically assigned by weighted moving average and ordered weighted averaging (WMA–OWA) combination algorithms. This model surpasses the limitations of existing approaches, wherein weights are assigned subjectively. The simulation results show that, compared with the existing approaches, the proposed model provides greater accuracy and a more detailed analysis in trust evaluation. [Copyright &y& Elsevier]

This research papers examines the state-of-the-art in the area of P2P networks/computation. It attempts to identify the challenges that confront the community of P2P researchers and developers, which need to be addressed before the potential of P2P-based systems, can be effectively realized beyond content distribution and file-sharing applications to build real-world, intelligent and commercial software systems. Future perspectives and some thoughts on the evolution of P2P-based systems are also provided. [ABSTRACT FROM AUTHOR]

Historically, the use of peer-to-peer (P2P) networks has been limited primarily to user-initiated exchanges of (mostly music) files over the Internet. This traditional view of P2P networks is changing, however, and the use of P2P networks has been suggested for delivering general-purpose content over the Web (or corporate intranets), even in real time. We analyze sharing in a P2P community in this new context under three different congestion measures: delay, jitter, and packet loss. Sharing is important to study in the presence of congestion because most existing research on P2P networks views congestion in the network as a relatively insignificant criterion. However, when delivering general-purpose content, congestion and its relationship to sharing is a critical factor that influences end-user performance. This paper looks at P2P networks from this new perspective by explicitly considering the effects of congestion on user incentives for sharing. We also propose a simple incentive mechanism that induces socially optimal sharing. [ABSTRACT FROM AUTHOR]

Abstract: Recently, Peer-to-Peer (P2P) networks have widely been used to file-sharing applications due to their decentralized architecture and reliability. The popularization of P2P networks also provides peers with ulterior motive an ideal environment to spread malicious files. In the past, many reputation systems have been proposed to differentiate malicious peers and to stop malicious file spreading. However, these reputation systems do not concern with reducing free riders in P2P networks. Free riders are peers who just download files but do not share anything to other peers. They significantly destroy the philosophy of P2P file-sharing networks. In this paper, we propose a free-rider aware reputation system for P2P file-sharing networks. Indeed, our reputation system can degrade the willing of free riders. Compared to most existing reputation systems, our reputation system provides an easy way to reduce malicious file spreading and free riding. [ABSTRACT FROM AUTHOR]

Peer-to-peer overlay networks are widely used in distributed systems. Based on whether a regular topology is maintained among peers, peer-to-peer networks can be divided into two categories: structured peer-to-peer networks in which peers are connected by a regular topology, and unstructured peer-to-peer networks in which the topology is arbitrary. Structured peer-to-peer networks usually can provide efficient and accurate services but need to spend a lot of effort in maintaining the regular topology. On the other hand, unstructured peer-to-peer networks are extremely resilient to the frequent peer joining and leaving but this is usually achieved at the expense of efficiency. The objective of this work is to design a hybrid peer-to-peer system for distributed data sharing which combines the advantages of both types of peer-to-peer networks and minimizes their disadvantages. The proposed hybrid peer-to-peer system is composed of two parts: the first part is a structured core network which forms the backbone of the hybrid system; the second part is made of multiple unstructured peer-to-peer networks each of which is attached to a node in the core network. The core structured network can narrow down the data lookup within a certain unstructured network accurately, while the unstructured networks provide a low-cost mechanism for peers to join or leave the system freely. A data lookup operation first checks the local unstructured network, and then, the structured network. This two-tier hierarchy can decouple the flexibility of the system from the efficiency of the system. Our simulation results demonstrate that the hybrid peer-to-peer system can utilize both the efficiency of structured peer-to-peer network and the flexibility of the unstructured peer-to-peer network and achieve a good balance between the two types of networks. [ABSTRACT FROM AUTHOR]

This paper presents an efficient approach for improving file availability in super-peer-based peer-to-peer (P2P) file-sharing systems. In the super-peer-based P2P file-sharing system, peers are organized into multiple groups. In each group, there is a special peer called super-peer to serve the regular peers within the same group. With this property, the proposed approach utilizes the super-peer to tolerate the departure (failure) of a regular peer in order to protect shared files. Unlike traditional replication-based approaches, the proposed approach keeps track of the file queries in the super-peer to support fault tolerance. The cost of tracking the file queries is much smaller than the cost of replicating the file contents in advance. Furthermore, the proposed approach uses a logical connection technique to consider the departure (failure) of the super-peer. Finally, simulation experiments are performed to quantify the performance and overhead of the proposed approach. [ABSTRACT FROM PUBLISHER]

In peer-to-peer (P2P) on-demand streaming networks, the alleviation of server load depends on reciprocal stream sharing among peers. In general, on-demand video services enable clients to watch videos from beginning to end. As long as clients are able to buffer the initial part of the video they are watching, on-demand service can provide access to the video to the next clients who request to watch it. Therefore, the key challenge is how to keep the initial part of a video in a peer's buffer for as long as possible, and thus maximize the availability of a video for stream relay. In addition, to address the issues of delivering data on lossy network and providing scalable quality of services for clients, the adoption of multiple description coding (MDC) has been proven as a feasible resolution by much research work. In this paper, we propose a novel caching scheme for P2P on-demand streaming, called Dynamic Buffering. The proposed Dynamic Buffering relies on the feature of MDC to gradually reduce the number of cached descriptions held in a client's buffers, once the buffer is full. Preserving as many initial parts of descriptions in the buffer as possible, instead of losing them all at one time, effectively extends peers' service time. In addition, this study proposes a description distribution balancing scheme to further improve the use of resources. Simulation experiments show that Dynamic Buffering can make efficient use of cache space, reduce server bandwidth consumption, and increase the number of peers being served. [ABSTRACT FROM AUTHOR]

In control system, tag table is like a dictionary mapping tagname to address. Therefore, applications on workstation may use tagname to access different data in system. Normally tag table generated by configuration software will transfer to other workstation in system manually after system configuration, which is inconvenient and fallible. The development of peer-to-peer (P2P) network technology and the realization of control system based on P2P network make the auto distribution of tag table possible. In this paper based on file sharing technology the presented method realizes the auto distribution of tag table. [ABSTRACT FROM AUTHOR]

Peer-to-peer (P2P) networks are very popular for large-scale data sharing in today's internet. It is naturally envisioned that the file sharing would also be an important application for civil mobile ad hoc networks in the future. The authors propose the cooperative diversity download methods utilising the wireless medium and common file sources in wireless P2P networks. The designed protocols including multi-source opportunistic direct downloading (MODD) and multi-source opportunistic decode-and-forward downloading (MODFD) can adaptively work in different file distribution scenarios. Both of them rely on the cooperation between the sources or receivers and the proposed distributed source-selection schemes. For the situation with one receiver and multi-source, MODD selects ‘best’ source with most favourite channel condition from available m sources. In the situation with multiple receivers and sources, the multiple receivers could form the cooperative pairs to receive the data from the selected source based on decode-and-forward transmission strategy. Compared with MODD, MODFD saves the source-selection time and provides incentives for the cooperation between the peers. A distributed collision solving scheme for the selection schemes is also proposed. The information theoretic analysis of outage probability shows that the proposed downloading methods can both obtain m times diversity gain. [ABSTRACT FROM AUTHOR]

In wireless mobile peer-to-peer (P2P) networks, multiple sources can provide multimedia file sharing at the same time. The selection of multiple sources is one of the key issues in the design of a multisource-transmission system in wireless mobile P2P networks. In this paper, we propose a distributed multisource sender-selection scheme to maximize the receiving data rate and minimize the energy consumption. Our scheme is based on recent advances in restless-bandit algorithms. The proposed sender-selection scheme has an indexability property that dramatically simplifies the computation and implementation of the policy. In addition, there is no need for a centralized control point, and senders can freely join and leave from the wireless mobile P2P network. Simulation results show that the proposed scheme significantly improves the receiving data rate and energy-consumption performance compared with the existing scheme. [ABSTRACT FROM AUTHOR]

Estimating the global data distribution in Peer-to-Peer (P2P) networks is an important issue and has not yet been well addressed. It can benefit many P2P applications, such as load balancing analysis, query processing, data mining, and so on. In this paper, we propose a novel algorithm which is based on compact multi-dimensional histogram information to achieve high estimation accuracy with low estimation cost. Maintaining data distribution in a multi-dimensional histogram which is spread among peers without overlapping and each part of which is further condensed by a set of discrete cosine transform coefficients, each peer is capable to hierarchically accumulate the compact information to the entire histogram by information exchange and consequently estimates the global data density with accuracy and efficiency. Algorithms on discrete cosine transform coefficients hierarchically accumulating as well as density estimation error are introduced with detailed theoretical analysis and proof. Our extensive performance study confirms the effectiveness and efficiency of our methods on density estimation in dynamic P2P networks. [ABSTRACT FROM AUTHOR]

Existing topology-aware methods have mostly the disadvantages of consuming large. amount of bandwidth, and needing complex calculations. For the purpose of resolving these problems, multi-level chord, or MLC, was proposed as a layered physical location-aware P2P network topology. MLC used a simple method that overlay network structure constructed by directly used physical network topology. This method ensured that nodes which were closer in overlay network were nodes which were closer in physical network, while avoiding the shortcomings of existing methods. Analysis showed through the layered topology mechanism and the role of GL(Group Leader) and SL(Slice Leader), that a better balance of the load can be achieved. With the bottom-up transmitting mechanism, the searching speed improved obviously. Period partial update algorithm can reduce some of the traffic. Experiments showed that MLC is a more effective network topology which has better performance than Chord in areas of hop in logical path, delay-time of physical path and average transfer time. [ABSTRACT FROM AUTHOR]

We consider the problem of update processing in a peer-to-peer (P2P) database network where each peer consists of an independently created relational database. We assume that peers store related data, but data has heterogeneity wrt instances and schemas. The differences in schema and data vocabulary are bridged by value correspondences called mapping tables. Peers build an overlay network called acquaintance network, in which each peer may get acquainted with any other peer that stores related data. In this setting, the updates are free to initiate in any peer and are executed over other peers which are acquainted directly or indirectly with the updates initiator. The execution of an update is achieved by translating, through mapping tables, the update into a set of updates that are executed against the acquainted peers. We consider both the soundness and completeness of update translation. When updates are generated and propagated in the network initiated from a peer, a tree is built dynamically called Update Dependency Tree (UDT). The UDT depicts the relationships among the component updates generated from the initial update. We also discuss the issues of the update propagation when a peer is temporarily unavailable or offline. Our propagation mechanism keeps track of a peer when the peer is not available for a certain period of time and once the peer comes back online the system propagates the updates destined to the returning peer to keep it's database synchronized. Moreover, conflict detection and resolution strategies have been proposed for such a dynamic P2P database network. We have implemented and experimentally tested a prototype of our update processing mechanism on a small P2P database network. We show the results of our experiments. [ABSTRACT FROM AUTHOR]

In this letter, we consider peer-to-peer (P2P) networks, where multiple peers are interested in sharing their content. In the considered P2P system, autonomous and self-interested peers use a Markov Decision Process (MDP) framework to determine their upload bandwidth allocations, which maximize their individual utilities. This framework enables the peers to make foresighted decisions on their bandwidth allocations, by considering the future impact of their decisions. In this letter, we focus on the impact of the peers' bounded rationality on their resource reciprocation strategies and ultimately, on their achievable utilities. Specifically, we consider peers who have only a limited ability to model the other peers' strategies for resource reciprocation, and study how this impacts their own decisions. [ABSTRACT FROM AUTHOR]

This paper presents a detailed examination of how the dynamic and heterogeneous nature of real-world peer-to-peer systems can introduce bias into the selection of representative samples of peer properties (e.g., degree, link bandwidth, number of files shared). We propose the Metropolized Random Walk with Backtracking (MRWB) as a viable and promising technique for collecting nearly unbiased samples and conduct an extensive simulation study to demonstrate that our technique works well for a wide variety of commonly-encountered peer-to-peer network conditions. We have implemented the MRWB algorithm for selecting peer addresses uniformly at random, into a tool called ion-sampler. Using the Gnutella network, we empirically show that ion-sampler yields more accurate samples than tools that rely on commonly-used sampling techniques and results in dramatic improvements in efficiency and scalability compared to performing a full crawl. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In a number of Internet applications, we need to search for objects to download them. This includes peer-to-peer (P2P) file sharing, grid computing and content distribution networks. Here the single object will be searched for in multiple servers. There are many searching algorithms in existence today for this purpose based on the concept of classical physics and classical algorithms. The principles of quantum mechanics can be used to build and analyze a quantum computer and its algorithms. Quantum searching is such an algorithm. In this paper we are proposing a search method based on the quantum physics and quantum algorithms. Our method, the targeted quantum search is found to be more cost effective than any other classical searching algorithms like linear and two-way linear, simulated annealing, including broadcast based searching. Our targeted quantum search method is analyzed and simulated to show the best results. [ABSTRACT FROM AUTHOR]

Network analysis has proved to be very useful in many social and natural sciences, and in particular Small World topologies have been exploited in many application fields. In this article, we focus on P2P file sharing applications, where spontaneous communities of users are studied and analyzed. We define a family of structures that we call "Affinity Networks" (or even Graphs) that show self-organized interest-based clusters. Empirical evidence proves that affinity networks are small worlds and shows scale-free features. The relevance of this finding is augmented with the introduction of a proactive recommendation scheme, namely DeHinter, that exploits this natural feature. The intuition behind this scheme is that a user would trust her network of "elective affinities" more than anonymous and generic suggestions made by impersonal entities. The accuracy of the recommendation is evaluated by way of a 10-fold cross validation, and a prototype has been implemented for further feedbacks from the users. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

BitTorrent has emerged as a very popular peer-to-peer file sharing system, which uses an embedded set of incentive mechanisms to encourage contribution and prevent free-riding. However, BitTorrent's ability to prevent free-riding needs further study. In this paper, we present a fluid model with two different classes of peers to capture the effect of free-riding on BitTorrent-like systems. With the model, we find that BitTorrent's incentive mechanism is successful in preventing free-riding in a system without seeds but may not succeed in producing a disincentive for free-riding in a system with a high number of seeds. The reason for this is that BitTorrent does not employ any effective mechanisms for seeds to effectively guard against free-riding. Therefore, we propose a seed bandwidth allocation strategy for the BitTorrent system to reduce the effect of seeds on free-riding. Finally, simulation results are given that validate what we have found in our analysis and demonstrate the effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

In this paper, we study both positive and negative scale effects on the operations of peer-to-peer (P2P) file sharing networks and propose the optimal sizing (number of peers) and grouping (number of directory intermediary) decisions. Using analytical models and simulation, we evaluate various performance metrics to investigate the characteristics of a P2P network. Our results show that increasing network scale has a positive effect on the expected content availability and transmission cost, but a negative effect on the expected provision and search costs. We propose an explicit expression for the overall utility of a content sharing P2P community that incorporates tradeoffs among all of the performance measures. This utility function is maximized numerically to obtain the optimal network size (or scale). We also investigate the impact of various P2P network parameters on the performance measures as well as optimal scaling decisions. Furthermore, we extend the model to examine the grouping decision in networks with symmetric interconnection structures and compare the performance between random- and location-based grouping policies. [ABSTRACT FROM AUTHOR]

We address the problem of highly transient populations in unstructured and loosely structured peer-to-peer (P2P) systems. We propose a number of illustrative query-related strategies and organizational protocols that, by taking into consideration the expected session times of peers (their lifespans), yield systems with performance characteristics more resilient to the natural instability of their environments. We first demonstrate the benefits of lifespan-based organizational protocols in terms of end-application performance and in the context of dynamic and heterogeneous Internet environments. We do this using a number of currently adopted and proposed query-related strategies, including methods for query distribution, caching, and replication. We then show, through trace-driven simulation and wide-area experimentation, the performance advantages of lifespan-based, query-related strategies when layered over currently employed and lifespan-based organizational protocols. While merely illustrative, the evaluated strategies and protocols clearly demonstrate the advantages of considering peers' session time in designing widely-deployed P2P systems. [ABSTRACT FROM AUTHOR]

Flooding is a fundamental file search operation in unstructured peer-to-peer (P2P) file sharing systems, in which a peer starts the file search procedure by broadcasting a query to its neighbors, who continue to propagate it to their neighbors. This procedure repeats until a time-to-live (TTL) counter is decremented to 0. Flooding can seriously limit system scalability, because the number of redundant query messages grows exponentially during the message propagation. Our study shows that more than 70 percent of the generated messages are redundant in a flooding with a TTL of 7 in a moderately connected Gnutella network. Existing efforts to address this issue have been focused on limiting the use of the flooding operation. We propose a new flooding scheme, called LightFlood, with the objective of minimizing the number of redundant messages and retaining a similar message-propagating scope as that of the standard flooding. In the scheme, each peer keeps track of the connectivities of every immediate and next indirect neighbor peers, which can be acquired locally. LightFlood identifies the neighbor with the highest connectivity and uses the link to that neighbor to form a suboverlay within the existing P2P overlay. In LightFlood, flooding is divided into two stages. The first stage is a standard flooding with a limited number of TTL hops, where a message can spread to a sufficiently large scope with a small number of redundant messages. In the second stage, message propagating is only conducted along the suboverlay, significantly reducing the number of redundant messages. Our analysis and simulation experiments show that the LightFlood scheme provides a low-overhead broadcast facility that can be effectively used in P2P search. For example, compared with standard flooding with seven TTL hops, we show that LightFlood with an additional two to three hops can reduce up to 69 percent of the flooding messages and retain the same flooding scope. We believe that LightFlood can be widely used as a core mechanism for efficient message broadcasting in P2P systems due to its near-optimal performance. [ABSTRACT FROM AUTHOR]

This paper develops a directed generalized random graphs based analytical modeling framework to compare several variations of the basic flooding search strategy in unstructured decentralized peer-to-peer networks. To validate the model predictions, we designed and implemented a distributed crawler architecture that is able to efficiently capture snapshots of the top-level Gnutella overlay topology. The snapshots are used to obtain simulation results that are used to assess the accuracy of our model. The model predictions are then used to compute system-oriented performance indexes (the average and the coefficient of variation of the number of query messages) as well as user-oriented measures (the probability of finding at least one replica of a resource, the average search time). The trade-off between the optimization of system-oriented measures and the improvement of user-oriented quality indexes is investigated for several variations of the basic flooding strategy suggesting that adding control parameters to the basic flooding mechanism might prove beneficial in this class of systems. Copyright © 2007 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The peer-to-peer (P2P) file-sharing applications are becoming increasingly popular and account for more than 70% of the Internet's bandwidth usage. Measurement studies show that a typical download of a file can take from minutes up to several hours depending on the level of network congestion or the service capacity fluctuation. In this paper, we consider two major factors that have significant impact on average download time, namely, the spatial heterogeneity of service capacities in different source peers and the temporal fluctuation in service capacity of a single source peer. We point out that the common approach of analyzing the average download time based on average service capacity is fundamentally flawed. We rigorously prove that both spatial heterogeneity and temporal correlations in service capacity increase the average download time in P2P networks and then analyze a simple, distributed algorithm to effectively remove these negative factors, thus minimizing the average download time. We show through analysis and simulations that it outperforms most of other algorithms currently used in practice under various network configurations. [ABSTRACT FROM AUTHOR]

In this paper, we propose a simple protocol for building heterogeneous unstructured peer-to-peer (P2P) networks. The protocol consists of two parts—the joining process and the rebuilding process. The basic idea for the joining process is to use a random walk to assist new incoming peers in selecting their suitable neighbors in terms of capacity and connectivity to achieve load-balancing. The rebuilding process specifies how the nodes should react when they lose links. In particular, we examine two representative schemes, namely the probabilistic-rebuilding scheme and the adaptive-rebuilding scheme. Furthermore, we provide a detailed analysis to investigate our proposed protocol under any heterogenous P2P environment. We prove that the topology structure of the P2P network depends heavily on the node heterogeneity. The analytical results are validated by the simulations. Our framework provides a guideline to engineer and optimize a P2P network in different respects under a heterogeneous environment. The ultimate goal of this paper is to stimulate further research to explore the fundamental issues in heterogeneous P2P networks. [ABSTRACT FROM AUTHOR]

In recent years, peer-to-peer (P2P) file-sharing systems have evolved to accommodate growing numbers of participating peers. In particular, new features have changed the proper- ties of the unstructured overlay topologies formed by these peers. Little is known about the characteristics of these topologies and their dynamics in modern file-sharing applications, despite their importance. This paper presents a detailed characterization of P2P overlay topologies and their dynamics, focusing on the modern Gnutella network. We present Cruiser, a fast and accurate P2P crawler, which can capture a complete snapshot of the Gnutella network of more than one million peers in just a few minutes, and show how inaccuracy in snapshots can lead to erroneous conclusions-such as a power-law degree distribution. Leveraging recent overlay snapshots captured with Cruiser, we characterize the graph-related properties of individual overlay snapshots and overlay dynamics across slices of back-to-back snapshots. Our results reveal that while the Gnutella network has dramatically grown and changed in many ways, it still exhibits the clustering and short path lengths of a small world network. Furthermore, its overlay topology is highly resilient to random peer departure and even systematic attacks. More interestingly, overlay dynamics lead to an "onion-like" biased connectivity among peers where each peer is more likely connected to peers with higher uptime. Therefore, long-lived peers form a stable core that ensures reachability among peers despite overlay dynamics. [ABSTRACT FROM AUTHOR]

Chapter 3 of the book "Foundations and Trends in Networking" is presented. The chapter explores the pros and cons of alternative peer-to-peer (P2P) computer content distribution networks (CDNs). The nature of the BitTorrent solution compared to the Microsoft Secure Content Distribution (MSCD) system, also known as Avalanche, is discussed. How Avalanche works, its advantages over BitTorrent and the challenges the network faces are outlined.