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Peer-to-Peer Computing (P2P), 2010 IEEE Tenth International Conference on

Date 25-27 Aug. 2010

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  • [Title page]

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  • List of papers

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  • Message from the General Co-Chairs

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  • Message from the Program Co-Chairs

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  • Acknowledgment of Sponsors

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  • Keynote speakers

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (291 KB)  

    Provides an abstract for each of the keynote presentations and a brief professional biography of each presenter. The complete presentations were not made available for publication as part of the conference proceedings. View full abstract»

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  • Online Data Backup: A Peer-Assisted Approach

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (268 KB) |  | HTML iconHTML  

    In this work we study the benefits of a peer- assisted approach to online backup applications, in which spare bandwidth and storage space of end- hosts complement that of an online storage service. Via simulations, we analyze the interplay between two key aspects of such applications: data placement and bandwidth allocation. Our analysis focuses on metrics such as the time required to complete a backup and a restore operation, as well as the storage costs. We show that, by using adequate bandwidth allocation policies in which storage space at a cloud provider can be used temporarily, hybrid systems can achieve performance comparable to traditional client-server architectures at a fraction of the costs. Moreover, we explore the impact of mechanisms to impose fairness and conclude that a peer-assisted approach does not discriminate peers in terms of performance, but associates a storage cost to peers contributing with little resources. View full abstract»

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  • PeerDedupe: Insights into the Peer-Assisted Sampling Deduplication

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (476 KB) |  | HTML iconHTML  

    As the digital data rapidly inflates to a world-wide storage crisis, data deduplication is showing its increasingly prominent function in data storage. Driven by the problems behind the mainstream server-side deduplication schemes, recently there has been a tendency of introducing peer-assisted methods into the deduplication systems. However, this topic is still quite vague at present and lacks thorough research. In this paper, we conduct in-depth and quantitative investigation on the peer-assisted deduplication. Through measurements we observe that the inter-peer duplication accounts for a large proportion of the total duplication, and exhibits strong peer locality. Then based on our observations, we propose PeerDedupe, a novel peer-assisted sampling deduplication approach. Experiments show that PeerDedupe can remove over 98% duplication with each peer coordinating with no more than 5 other peers, and it requires much less server RAM usage than the existing works. View full abstract»

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  • Optimizing Near Duplicate Detection for P2P Networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (682 KB) |  | HTML iconHTML  

    In this paper, we propose a probabilistic algorithm for detecting near duplicate text, audio, and video resources efficiently and effectively in large-scale P2P systems. To this end, we present a thorough cost and probabilistic analysis that allows the algorithm to adapt to network and data collection characteristics for minimizing network cost. In addition, we extend the algorithm so that it can identify similar videos, even if some of the videos are split into different files. A thorough theoretical analysis as well as a large-scale experimental evaluation on networks of up to 100,000 peers using real-world datasets of more than 200 Gbytes demonstrate the viability of our approach. View full abstract»

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  • Availability and Redundancy in Harmony: Measuring Retrieval Times in P2P Storage Systems

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (247 KB) |  | HTML iconHTML  

    Peer-to-peer (P2P) storage systems are strongly affected by churn - temporal and permanent peer failures. Because of this churn, the main requirement of such systems is to guarantee that stored objects can always be retrieved. This requirement is specially needed in two main situations: when users want to access the stored objects or when data maintenance processes have to repair lost information. To meet this requirement, exiting P2P storage systems introduce large amounts of redundancy that maintain data availability close to 100%. Unfortunately, these large amounts of redundancy increase the storage costs, either by reducing the overall net capacity or by increasing the communication required for data maintenance. In order to minimize storage costs, P2P storage systems can reduce data redundancy. However, less redundancy means lower data availability, which leads to increase object retrieval times. Unfortunately, longer retrieval times could compromise data maintenance processes and could penalize user's retrieval times. It is crucial then for P2P storage systems to predict the effects of a redundancy reduction. In order to provide this information, we present a novel analytical framework to measure object retrieval times under different redundancy and churn circumstances. Our framework can be directly used by backup applications aiming to maintain durability at the lower cost, or by data sharing applications that seek to reduce costs by penalizing user retrieval times. We validate our framework by simulation using real P2P traces (Skype and eMule's KAD). View full abstract»

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  • Analyzing the DC File Sharing Network

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB) |  | HTML iconHTML  

    This paper investigates the Direct Connect (DC) file sharing network, which to the best of our knowledge, has never been academically studied before. We developed a participating agent, in order to gather protocol specific information. We quantify network characteristics such as distribution of users in hubs, hubs geography, queries distribution and trends in shared folder size. We also characterize the typical DC user: A heavy downloader with a particularly large shared folder. Most importantly, we discovered a query duplications problem that drains much of the hubs CPU and bandwidth resources. In the DC network, query facilitation is the most demanding task for hubs and the main factor in the protocol's scalability challenges. We show that in some hubs, up to a third of the queries traffic is duplicated and therefore wasteful. Resolving this problem will dramatically improve hubs performances by reducing the amount of relayed queries and thus permitting larger hub communities. View full abstract»

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  • Spring for Vivaldi -- Orchestrating Hierarchical Network Coordinates

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (234 KB) |  | HTML iconHTML  

    Network coordinates have become an important building block for efficient peer-to-peer applications. They allow the peers to determine those other peers to whom they are likely to experience a low round trip time. So they can preferably attach to these selected peers and thereby create efficient overlay structures. Despite the substantial interest in this topic, there is still room for improvement. In this paper we propose Hierarchical Vivaldi, a variant of the popular Vivaldi algorithm. It predicts the peers' embedding error so that it can optimize the peer selection process. We conducted extensive studies with several sets of Internet traffic traces. They compare our proposal to Vivaldi and its previously proposed optimizations. Our results show that Hierarchical Vivaldi can improve the accuracy of the RTT predictions by an order of magnitude. View full abstract»

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  • Measurement and Analysis of BitTorrent Traffic in Mobile WiMAX Networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (477 KB) |  | HTML iconHTML  

    As mobile Internet environments are becoming dominant, how to revamp P2P operations for mobile hosts is gaining more and more attention. In this paper, we carry out empirical traffic measurement of BitTorrent service in various settings (static, bus and subway) in commercial WiMAX networks. To this end, we analyze the connectivity among peers, the download throughput/stability, and the signaling overhead of mobile WiMAX hosts in comparison to a wired (Ethernet) host. We find out the drawbacks of BitTorrent operations in mobile Internet are characterized by lower connection ratio, unstable connections amongst peers, and higher control message overhead. View full abstract»

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  • Do BitTorrent-Like VoD Systems Scale under Flash-Crowds?

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (175 KB) |  | HTML iconHTML  

    The efficiency of BitTorrent for file sharing has inspired a number of BitTorrent-based P2P protocols for Video-on-Demand (VoD). It has been shown that these systems are scalable in steady-state: the service quality provided to the users does not depend on the number of users in the system. However, it is not well understood how these systems scale under flash-crowds. In this work, we model a general BitTorrent-like VoD system and we find that under a flash-crowd the quality-of-service (QoS) degrades with the number of users. Also, our analysis shows that, at the very beginning of a flash-crowd, the maximum number of simultaneous users that can obtain a given service level is intrinsically related to two fundamental system parameters, namely the initial service capacity and the efficiency of piece exchange of the underlying P2P protocol. Finally, we illustrate the impact of peers turning into seeders (i.e peers that have finished downloading and remain in the system to upload) on the system scale. View full abstract»

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  • Waiting for Anonymity: Understanding Delays in the Tor Overlay

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (303 KB) |  | HTML iconHTML  

    Although Tor is the most widely used overlay for providing anonymity services, its users often experience very high delays. Because much of Tor usage is for Web applications, which are sensitive to latency, it is critical to reduce delays in Tor. To take an important step in this direction, we seek an in-depth understanding of delays in Tor. By taking snapshots of the entire Tor network within a short time window, we are able to study the delay distribution of the entire router population. We also monitor delays introduced by individual Tor routers over extended periods of time. Our results indicate that apart from delays introduced by routers, overlay network latency also plays a significant role in delays in Tor. We have also observed that at any time, there exist huge differences in the delays introduced by different routers. Our results reveal key performance characteristics of Tor system behavior and provide valuable insights for improving the Tor performance. View full abstract»

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  • Autonomous NAT Traversal

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (177 KB) |  | HTML iconHTML  

    Traditional NAT traversal methods require the help of a third party for signalling. This paper investigates a new autonomous method for establishing connections to peers behind NAT. The proposed method for autonomous NAT traversal uses fake ICMP messages to initially contact the NATed peer. This paper presents how the method is supposed to work in theory, discusses some possible variations, introduces various concrete implementations of the proposed approach and evaluates empirical results of a measurement study designed to evaluate the efficacy of the idea in practice. View full abstract»

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  • Verifiable Encryption for P2P Block Exchange

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (109 KB) |  | HTML iconHTML  

    Free-riding is an important problem in Peer-to-Peer (P2P) file-sharing networks. When peers refuse to contribute upload bandwidth, the whole network can collapse. A relatively new free-riding vulnerability in BitTorrent is the Large View Exploit, in which a peer connects to as many other peers as possible to increase the chance to get free data. This exploit can not be thwarted by tit-for-tat-like mechanisms which have traditionally been used to ban free-riding. Several approaches have been proposed to combat the Large View Exploit in fully decentralized systems, most of which rely on encryption. However, the use of regular encryption makes it impossible to verify the correctness of received data. In this paper we propose a novel encryption method which does allow verification of the plaintext data without decryption, at the expense of encryption strength. We show that a colluding peer still has to send data that is at least 40% of the size of the original data to allow decryption. View full abstract»

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  • The Impact of Caching on BitTorrent-Like Peer-to-Peer Systems

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (192 KB) |  | HTML iconHTML  

    Peer-to-peer file-sharing systems are responsible for a significant share of the traffic between Internet service providers (ISPs) in the Internet. In order to decrease their peer-to-peer related transit traffic costs, many ISPs have deployed caches for peer-to-peer traffic in recent years. We consider how the different types of peer-to-peer caches - caches already available on the market and caches expected to become available in the future - can possibly affect the amount of inter-ISP traffic. We develop a fluid model that captures the effects of the caches on the system dynamics of peer-to-peer networks, and show that caches can have adverse effects on the system dynamics depending on the system parameters. We combine the fluid model with a simple model of inter-ISP traffic and show that the impact of caches cannot be accurately assessed without considering the effects of the caches on the system dynamics. We identify scenarios when caching actually leads to increased transit traffic. Our analytical results are supported by extensive simulations and experiments with real BitTorrent clients. View full abstract»

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  • Unraveling BitTorrent's File Unavailability: Measurements and Analysis

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (804 KB) |  | HTML iconHTML  

    BitTorrent suffers from one fundamental problem: the long-term availability of content. This occurs on a massive-scale with 38% of torrents becoming unavailable within the first month. In this paper we explore this problem by performing two large-scale measurement studies including 46K torrents and 29M users. The studies go significantly beyond any previous work by combining per-node, per-torrent and system-wide observations to ascertain the causes, characteristics and repercussions of file unavailability. The study confirms the conclusion from previous works that seeders have a significant impact on both performance and availability. However, we also present some crucial new findings: (i) the presence of seeders is not the sole factor involved in file availability, (ii) 23.5% of nodes that operate in seedless torrents can finish their downloads, and (iii) BitTorrent availability is discontinuous, operating in cycles of temporary unavailability. View full abstract»

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  • Can P2P-Users Benefit from Locality-Awareness?

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB) |  | HTML iconHTML  

    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 simultaneously increase the performance from the viewpoint of the P2P users, i.e, shorten download times. This win-win situation should be achieved by a preferred exchange of information between peers which are located closely 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 assume mostly homogeneous peer distributions and that all peers have the same access speed. This is not the case in practice according to several measurement studies. Therefore, we extend previous work in this paper by studying scenarios with real-life, skewed peer distributions and heterogeneous access bandwidths of peers. 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 depends heavily on the used locality-aware peer selection and the concrete scenario. Therefore, we conclude that current proposals need to be refined so that users of P2P networks can be sure that they also benefit from their use. Otherwise, a broad acceptance of the concept of locality-awareness in the user community of P2P networks will not take place. View full abstract»

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  • On Tracker Selection for Peer-to-Peer Traffic Locality

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    BitTorrent (BT) is an extremely successful peer-to-peer (P2P) application providing efficient file sharing over the Internet. The ever-increasing traffic among the peers has also put unprecedented pressure to Internet Service Providers (ISPs). P2P locality has therefore been widely suggested, which explores finding local resources to optimize the cross-ISP/AS traffic. However, the ISPs would fail to reduce the cross-AS traffic if they could not control the neighbor selection of their P2P subscribers. In this paper, we examine the applicability of P2P locality through real-world measurement. We find that the widely deployed load balance trackers will greatly reduce the efficiency of traffic locality. Due to peers' random tracker selection, there is no grantee that the peers will always choose the modified trackers as we expected. To make the matter worse, some Internet trackers involve serious copyright violation and may hardly cooperate with the ISPs. Fortunately, our investigation of the AS-Tracker relationship indicates that if we carefully select the trackers during the locality deployment, most peers can still be controlled by the ISPs with relatively high probability. A machine learning based model is then proposed to quantify the similarity of trackers' peer distribution. Our trace-based simulation shows that, the similarity value can provide useful hints to enhance P2P locality. In particular, the peers are more likely to be optimized with higher probability. Moreover, the learning of tracker similarity does not require the global knowledge of Internet trackers, which can hardly be obtained by the individual ISPs. View full abstract»

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  • Cryptographically Enforced Permissions for Fully Decentralized File Systems

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (552 KB) |  | HTML iconHTML  

    Distributed file systems nowadays work well in many ways. They provide efficient solutions, for example, to distribute data among a global team. But most systems do not address the complex subject of secure user and group management. The systems that do, usually offer only a very limited subset of access permissions that is incompatible to the permissions usually used in Unix-like systems. In this paper, we propose a new system for user and group management, which cryptographically enforces access permissions in fully decentralized file systems. Our proposal is twofold: an integrity verification algorithm checks the validity of the current file system state; a cryptographic data protection scheme, added on top of the integrity verification, preserves the privacy of the file system content. Except for signatures, our system uses symmetric cryptography only. It thus incurs only a reasonable cryptographic cost in the system. View full abstract»

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  • Distributed Access Enforcement in P2P Networks: When Privacy Comes into Play

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (255 KB) |  | HTML iconHTML  

    In open environments such as peer-to-peer networks, the decision to collaborate with multiple users (e.g., by granting access to a resource) is hard to achieve in practice due to extreme decentralization. The literature contains a plethora of examples where a scalable solution for access control is basic to spur their adoption.Motivated by this need, we introduce a novel protocol to enforce access control in a distributed but also privacy-preserving manner - i.e., so as to minimize the disclosure of privileges and of access policies. Privacy is rather scarce in peer-to-peer systems, for which we believe that our protocol is a valuable contribution. Using extensive simulations on top of real Internet topologies, we illustrate the applicability of our protocol, which is efficient both in terms of communication and rounds of interaction. View full abstract»

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