【作者】 张杰；

【导师】 赵政；

【作者基本信息】 天津大学 ， 计算机应用技术， 2007， 博士

【摘要】 近些年来P2P系统受到越来越多的关注。P2P网络的一个重要目标就是系统内所有用户共享各自的资源,如计算能力、网络带宽、存储空间、内容。目前大多数P2P系统都是建立在用户愿意提供共享资源的假设之上的,这一假设忽视了节点出于自身利益考虑不按既定协议行事的能力。相关研究发现,理性和自私性是节点不可忽视的本性,节点的自利行为导致了P2P网络内很严重的问题,如搭便车和公共物品的悲剧等。为了解决这些问题,越来越多的研究投入了这个领域。目前的研究成果大致可以分为两个方向:一种是基于概率估计的信誉管理模型,另一种是基于博弈论的激励机制。本文提出的半结构化的解决方案结合了以上两种技术,将节点分为两类:精英节点和普通节点。精英节点组成结构化网络,通过一个微支付平台有偿交换服务;普通节点组成无结构网络,通过基于推荐的信誉管理机制管理服务。其中,微支付平台分为两层:定价层和清算层。在定价层,假设所有参与节点都是理性的和自私的,然后根据经济学已有的激励相容的Vickrey-Clarke- Groves机制提出一个能够最大化网络总体效用的定价机制。此机制可以在O(n)的时间复杂度内满足以下特性:1)激励相容,每个节点都能够如实的汇报自己的网络连接状况;2)个体理性;3)完全分布式,多个服务提供者和多个服务请求者能够同时进行服务和信息交互。在清算层,将每个节点的服务信息存储在多个第三方节点上,这些节点组成一个远程的、分布的、冗余的银行节点集。仿真实验的结果表明了这套解决方案的有效性和健壮性。在避免过多网络开销的情况下能够有效的配置节点资源。另外,虽然此机制是建立在节点理性的假设基础之上,但节点理性并不是一个必要条件,此机制面对节点的恶意行为仍具有一定的健壮性。更多还原

【Abstract】 Peer-to-Peer (P2P) systems are receiving considerable interest in recent years. An important goal in P2P networks is that all peers provide resources, including computing power, bandwidth, storage space, and content. Most of the existing P2P networks are typically designed around the assumption that all peers are most willingly to contribute their resources and assist others. This assumption ignores the peers’ability to modify the behavior of an algorithm for self-interested reasons. However, as experience with P2P networks shows, rationality and selfishness are real issues in P2P networks. Selfish behaviors of peers may lead to serious problems of P2P network, such as free-riding and tragedy of commons.In order to solve these problems, there are increasing considerations on reputation system design in the study of P2P networks. The current work in the field can be roughly divided into two groups. One is reputation-based trust models that rely on the well known probabilistic estimation techniques use only a limited fraction of the available feedback. The other is game theory based incentive mechanisms that rely on aggregating the entire available feedback in the social network in hope achieving as much robustness against possible misbehavior as possible.In our work, we combined both techniques into a semi-structured mechanism which divide all the peers into 2 parts: super peers and normal peers. Super peers compose a structured P2P network using a micro-payment platform that we design to exchange services. While, normal peers compose an unstructured P2P network using a recommonand-based trust model.The micro-payment platform that we mentioned above has two layers: pricing layer and accounting layer.In pricing layer, we provide a general pricing mechanism that can maximize P2P networks’social welfare in a way of Vickrey-Clarke-Groves family, while assuming every peer in P2P networks is rational and selfish. This pricing mechanism has some desirable properties using an O(n) algorithm: (1) incentive compatibility, every peer truly report its connection type; (2) individually rationality; and (3) fully decentralized, we design a multiple-provider multiple consumer model, concerning about the service provider and service consumer individually.In accounting layer, we storage each peer’s account information in several third party peers. These peers are chosed by a remote, distributed, and redundant way.Simulation results show the efficiency and robustness of our mechanism. This solution can deploy peers’resource efficiently with rational overhead. Additional, individual rationality is not necessary condition of our mechanism. This solution can deal with malicious behaviors well.更多还原