MobiStore: A system for efficient mobile P2P data sharing

MobiStore is a P2P data store for decentralized mobile computing, designed to achieve high availability and load balance. As P2P platforms, mobile devices connected to the Internet through WiFi or cellular networks are different from wired devices in two main aspects: (1) higher churn due to mobility, weak wireless signals, or battery constraints, and (2) significant variability in bandwidth and latency based on the point of attachment. These problems affect the stored content availability and skew the content serving load over the peers. MobiStore structures the mobile P2P network into clusters of redundant peers. The topology uses both algorithmically-defined and random edges among the peers of different clusters. The routing information is updated using a gossip-based protocol. Thus, MobiStore achieves, with high probability, O(1) lookup operations despite high churn and link variability. Inside the clusters, all peers replicate the content, which improves the content availability. Furthermore, based on the current load, MobiStore dynamically changes the number of peers inside the clusters and routes content request to randomly selected peers. These two dynamic techniques along with using consistent hashing to map content to peers balance the load over the peers. While some of these techniques are well known, the main contribution is on the novel ways of applying them to design and implement an efficient mobile P2P data store. Simulation results show MobiStore achieves an availability, i.e., lookup success rate, between 12–48 % higher than two baseline systems built over the MR-Chord and Chord P2P protocols; and it reduces the latency up to 9 times compared to these protocols. Finally, the results show MobiStore adapts to churn and workload to evenly distribute the requests across clusters and peers better than both baseline solutions.     

Adaptive resource scheduling mechanism in P2P file sharing system

Due to the inefficient resource adjustment, the current P2P file sharing systems cannot achieve the balanced relationship between supplements and demands over the resources. In this case, the uploading bandwidth of the system node cannot be utilized efficiently and the overall system QoS is degraded. In this paper, an adaptive resource scheduling mechanism called Push mechanism, is proposed, in which “proactive” strategies are provided to handle the unbalance supplement-demand relationship of some resource. Specifically, the system firstly forecasts which resource will becoming insufficient, then it pre-increase the uploaders over such resource so that the system performance is improved. Through numerical practical experiment in download platform of Tencent, it is proved that the proposed mechanism increases the downloading rate, saves the traffic on the server and optimizes the system performance.     

利用审计方式构建公平的对等文件共享系统

利用审计方式构建了一个公平的对等文件共享系统。该共享模式参考了市场经济的交易模型,结合了文件共享中的限额管理技术,通过描述节点的信任度信息让其能够存储更多的文件,使节点能够发布它的资源使用记录,其他的节点就可以通过某个功能来审计这些记录的情况,以保证交易的正确性和可追溯性,实现资源上传下载的公平性。描述了审计模型的工作机制和代价分析,构建了审计模型的测试环境,性能分析表明,在大量的节点和文件进行上传和下载的时候,系统具有比较小的通信延迟和良好的扩展性,优于同类的非审计模式。     

P2P文件共享系统行为特性分析和研究

P2P文件共享系统的行为特性对于系统的健壮性和可靠性起着重要的作用,在设计和部署P2P文件共享系统时必须考虑这些问题。 为了解P2P文件共享系统中的行为特性,对其形成原因和产生作用进行了分析,并对其中的一些行为做了测量和比较,总结了这些行为的变化特点,以及目前对其有效的应对措施。     

Energy efficient peer-to-peer file sharing

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

P2P as a CDN: A new service model for file sharing

Traditional content distribution networks (CDNs), such as Akamai, replicate content at thousands of servers worldwide in an attempt to bring it closer to end users. Recent years have, however, brought a surge of peer-to-peer (p2p) systems that have demonstrated the ability both to help traditional CDN operations and to effectively disseminate content as independent applications. Unfortunately, this p2p surge has created significant problems to network operators by generating large volumes of inter-AS traffic. In this paper, we demonstrate that stepping back and applying traditional CDN design principles to p2p systems can help solve these emerging problems. In particular, focusing on the BitTorrent swarming protocol, we show that our new service model can, in the common case, reduce inter-AS traffic by 45–75%. Moreover, in scenarios when ISPs are shaping inter-AS traffic, it speeds up download times by 60% for the most popular torrents.Our approach bases on disproving the common wisdom that the current peer altruism in p2p systems (BitTorrent in particular) is insufficient. We thus abandon the common approach of deploying novel incentives for cooperation, and focus on designing methods to effectively utilize existing system resources. We show that controlled regional-based content replication, common for the traditional CDN design, can effectively achieve this goal. We implement our system and demonstrate that it effectively scales. Moreover, it is incrementally deployable and brings significant benefits in partial deployment scenarios. ISPs and network regions in which the system gets deployed can resolve their inter-AS traffic problems instantly and autonomously, i.e., without any inter-ISP collaboration and without requiring that the system gets deployed in the entire Internet.     

基于JXTA的P2P文件共享系统安全性的研究

文件共享是P2P技术主要的应用领域之一,JXTA是P2P应用的一个开发平台,本文在现有的文件共享模型并基于JX-TA协议集、评价反馈机制基础上,加入JXTA用户认证、Poblano安全模型的传播信任机制。实现一个更安全的基于JXTA平台的P2P文件共享系统的应用模型。     

ARES P2P资源共享协议分析技术研究

近年来,内容服务提供商提出离线下载的缓存服务解决方案,旨在大幅度提升对等（Peer-to-Peer,P2P）文件传输性能,解决长期以来由拓扑失配所导致的性能下降问题。而实现缓存服务解决方案的关键在于对P2P协议的分析。针对在南美区域较为流行的ARES协议展开技术研究。首先采用小波支持向量机模型将ARES P2P协议报文从抓取到的网络报文中进行分离,然后综合各类逆向协议分析的方法和技术分析出完整的ARES P2P协议报文格式和报文发送时序。最后,通过ARES离线下载实验验证ARES P2P协议分析的正确性和完整性。     

A conservative strategy to protect P2P file sharing systems from pollution attacks

Despite being currently one of the main Internet applications, P2P file sharing has been hampered by content pollution attacks. To tackle this problem, we introduce a novel pollution control strategy that consists in adjusting the rate in which content is disseminated, according to content version reputation. The proposed strategy is modeled and evaluated using simplifying assumptions. Then, inspired by classic distributed designs, we propose a pollution control mechanism that implements such a strategy. The mechanism is evaluated in terms of the delays imposed on non‐polluted version dissemination, the effectiveness of reducing dissemination when the version is polluted, and the negative impact that collusion attacks can impose on the reputation system upon which our mechanism is built. Simulation results looking at scenarios with several hundred peers indicate that the pollution control mechanism can effectively reduce pollution without substantially affecting the dissemination of non‐polluted content. Copyright © 2010 John Wiley & Sons, Ltd.     

ExtSFR: scalable file recovery framework based on an Ext file system

Multimedia Tools and Applications - As the technologies based on the Internet of Things, the Cloud, Big Data, and mobile technology have recently become the engine of the next-generation fusion...     

基于数据基因的P2P文件共享平台

定义了适用于P2P文件共享的数据基因模型,并给出了基于数据基因模型的P2P文件共享平台的体系结构。这一文件共享平台利用文件的数据基因组来组织和管理共享文件。由于同一文件的不同版本拥有不同的基因信息,它们可同时存在于系统中供用户使用,因此数据一致性问题得到简化。由于可利用文件数据基因组中对相关文件的记录进行查询处理,系统查询实现更高效。文中还给出了此文件共享平台的数据查询算法与更新策略。     

一种嵌入式P2P文件共享系统

论述Windows CE嵌入式平台上一种P2P文件共享系统的实现。并针对嵌入式平台的特点,对该文件共享系统进行了优化,提出两种优化方法：充分利用内存资源和改善排队算法。前者解决嵌入式平台I/O操作速度慢的问题,后者解决嵌入式系统Socket资源受限的问题。测试结果表明,这些优化方法有效地改善了文件共享系统的性能,提高了文件下载速率。     

面向MassStorage类设备的易裁剪文件系统设计

为节约有限的Flash存储资源,快速有效地移植嵌入式文件系统,以满足不同USB主机系统的实际应用需求,在分析Bulk-Only传输协议、MassStorage类协议以及FAT12/16/32文件格式的基础上,提出了一种软件层次清晰、易于裁剪、对操作系统无依赖的嵌入式文件系统设计方法。该方法明确划分了文件系统各功能模块,合理封装了各模块的对外接口函数,并对文件系统类型识别、簇空间分配以及长文件名等问题进行了有效处理。通过设计一个以Freescale ColdFire系列芯片MCF52223为主控芯片的道闸管理系统,表明了该方法的可行性和有效性。     

HD Tree: A novel data structure to support multi-dimensional range query for P2P networks

There are two basic concerns for supporting multi-dimensional range query in P2P overlay networks. The first is to preserve data locality in the process of data space partitioning, and the second is the maintenance of data locality among data ranges with an exponentially expanding and extending rate. The first problem has been well addressed by using recursive decomposition schemes, such as Quad-tree, K-d tree, Z-order, and Hilbert curve. On the other hand, the second problem has been recently identified by our novel data structure: HD Tree. In this paper, we explore how data locality can be easily maintained, and how range query can be efficiently supported in HD Tree. This is done by introducing two basic routing strategies: hierarchical routing and distributed routing. Although hierarchical routing can be applied to any two nodes in the P2P system, it generates high volume traffic toward nodes near the root, and has very limited options to cope with node failure. On the other hand, distributed routing concerns source and destination pairs only at the same depth, but traffic load is bound to some nodes at two neighboring depths, and multiple options can be found to redirect a routing request. Because HD Tree supports multiple routes between any two nodes in the P2P system, routing in HD Tree is very flexible; it can be designed for many purposes, like fault tolerance, or dynamic load balancing. Distributed routing oriented combined routing (DROCR) algorithm is one such routing strategy implemented so far. It is a hybrid algorithm combining advantages from both hierarchical routing and distributed routing. The experimental results show that DROCR algorithm achieves considerable performance gain over the equivalent tree routing at the highest depth examined. For supporting multi-dimensional range query, the experimental results indicate that the exponentially expanding and extending rate have been effectively controlled and minimized by HD Tree overlay structure and DROCR routing.     

Overlay networks: A scalable alternative for P2P

Overlay networks create a structured virtual topology above the basic transport protocol level that facilitates deterministic search and guarantees convergence. Overlay networks are evolving into a critical component for self-organizing systems. Here we outline the differences between flooding-style and overlay networks, and offer specific examples of how researchers are applying the latter to problems requiring high-speed, self-organizing network topologies.     

An efficient scheduling algorithm for scalable video streaming over P2P networks

During recent years, the Internet has witnessed rapid advancement in peer-to-peer (P2P) media streaming. In these applications, an important issue has been the block scheduling problem, which deals with how each node requests the media data blocks from its neighbors. In most streaming systems, peers are likely to have heterogeneous upload/download bandwidths, leading to the fact that different peers probably perceive different streaming quality. Layered (or scalable) streaming in P2P networks has recently been proposed to address the heterogeneity of the network environment. In this paper, we propose a novel block scheduling scheme that is aimed to address the P2P layered video streaming. We define a soft priority function for each block to be requested by a node in accordance with the block’s significance for video playback. The priority function is unique in that it strikes good balance between different factors, which makes the priority of a block well represent the relative importance of the block over a wide variation of block size between different layers. The block scheduling problem is then transformed to an optimization problem that maximizes the priority sum of the delivered video blocks. We develop both centralized and distributed scheduling algorithms for the problem. Simulation of two popular scalability types has been conducted to evaluate the performance of the algorithms. The simulation results show that the proposed algorithm is effective in terms of bandwidth utilization and video quality.     

P2P下的大型流媒体文件分发共享机制研究

利用CDN网络进行大型流媒体的分发会由于代理服务器存贮空间的有限性而造成应用性能的下降。基于文件分段共享方案的提出从一定程度上缓解了这种矛盾,但并没有从根本上解决它。而P2P网络的提出及基于P2P主机来构建CDN网络却为这个问题的解决提供了可行性。正是基于这一观点提出了一种在基于P2P节点主机构建的CDN网络上进行大型流文件分发共享的方案。由于是基于P2P节点主机构建,因此这种网络的存贮容量接近于“无限”,而CDN网络中节点主机的“动态性”促使在选择文件段的存贮位置及其后的流文件调度机制中都需考虑节点的“剩余寿命”。与原有的基于代理服务器构建的CDN网络上的文件段共享方案相比,本方案具有更好的性能,主要体现在具有更加稳定的系统服务容量和更高的服务完成率。模拟实验证明了这一点。