【作者】 田慧蓉；

【导师】 程时端；

【作者基本信息】 北京邮电大学 ， 计算机应用技术， 2006， 博士

【摘要】 随着Internet的广泛普及，端用户系统资源的丰富，以及网络带宽的快速增加，传统的Client／Server网络应用模式中服务器的性能瓶颈以及单点失效的问题不仅限制了端系统资源的充分利用，同时越来越无法满足新的分布式应用的需求。而Peer-to-Peer(P2P)网络在协同工作，分布式信息共享，大规模并行计算等方面显示出独特优势，使其成为新的发展热点。P2P网络是基于节点愿意共享资源这一基本假设的，但实际情况是P2P网络这种公共物品的私人提供导致了P2P网络中存在着free-riding问题和公共物品的悲哀问题。事实上，P2P网络的理性用户更多地表现出自兴趣和自主性，其根本目的是最大化自己效用，而并不考虑网络的整体效用。此外，P2P网络中存在着大量不可靠的服务质量以及欺诈行为。因此，要提高P2P网络的性能必须考虑节点的自主行为，激励节点之间有效合作并合理使用网络资源。本论文围绕P2P网络中节点自主行为造成的不可靠服务质量和不合作问题进行了研究，主要工作包括以下几个方面： (1)针对P2P网络拓扑构造时没有充分考虑free-rider和恶意节点的问题，提出了基于节点互惠能力的自适应P2P拓扑构造协议RC-ATP。该协议充分考虑节点构造拓扑的理性，即节点只愿意与能为其带来利益的节点建立连接，基于节点提供服务的能力和推荐服务提供者的能力定义了节点的互惠能力，使得具有互惠关系的节点能够充分建立连接。同时，RC-ATP响应选择机制减小了节点下载不可信文件的概率。仿真分析表明，利用该协议构造的拓扑实现了对合作节点的激励以及对free-rider和恶意节点的遏制，具有激励一致性。此外，该网络拓扑比已有同类拓扑APTP具有更好的有效性和抗攻击能力。尽管RC-ATP拓扑调整开销比APTP稍大，但RC-ATP的整个网络开销更小。 (2)针对大规模P2P网络中节点之间由于兴趣的不对称发生重复交易的可能性较小，而导致节点之间难以直接建立信任关系，使得网络容易受到恶意节点攻击的问题，本文提出了基于群组的信任模型GroupRep。该信任模型将信任关系划分为群组之间的信任关系，群组与节点之间的信任关系和节点之间的信任关系三个层次。节点利用本地信任信息或有限时间内可获取的所属群组的推荐信任信息更多还原

【Abstract】 Peer-to-Peer(P2P) has become the overwhelming technology for the internet as its benefits over traditional client-server approaches to cooperative working, data sharing and large scale parallel computing. The basic assumption of P2P networks is that peers are willing to share resoures with others. However, the realitiy is that the private provision of public goods causes free-riding and the tragedy of the commons in P2P networks. In fact, the rational users of P2P networks are self-interest and self-determination. The object of them is to maximize the personal utility without considering the whole network productivity. In addition, there still exist a large amount of P2P services with unreliable qualities and malicious actions. Therefore, to improve the performance of P2P networks, the peers’ voluntary operations must be taken into account as well as the incentive mechanism which incent peers cooperate and consume resources rationally. This dissertation studies the problems of unrealiable services and uncooperation in P2P networks, and results in the following achievements:(1) A Reciprocal Capacity based Adaptive Topology Protocol (RC-ATP) for P2P networks is proposed in this thesis. It is based on the rational belief that a peer is only willing to maintain connections with those which will benefit it in future. Reciprocal capacity is defined based on peers’ capacity of providing services and of recommending service providers. As a result, reciprocal peers connect each other adequately. In addition, a response selction mechanism is proposed to reduce the probability of trying to download files from malicious peers. Therefore, the resulting topologies are more efficient and resilient than Adaptive Peer-to-Peer Topologies (APT). Furthermore, RC-ATP has the intrinsic incentive to active peers as they are more advantaged and important in the network than free-riders and malicious peers. Although the overhead of the topology adaptation is a bit higher, RC-ATP works more efficiently with less cost compared with the Adaptive Peer-to-Peer Topologies Protocol (APTP).(2) A group based reputation system GroupRep for P2P networks is proposed. In更多还原