P2P网络流媒体关键技术

P2P网络流媒体技术一直是学术界和产业界的研究热点.本文围绕覆盖网络拓扑结构,对现有的P2P流媒体系统作了全面的归类总结,深入介绍和分析了覆盖网络构建、数据块调度策略等P2P流媒体核心技术,并概要讨论视频编码、网络编码、覆盖网络拓扑优化、安全与激励机制等P2P流媒体相关增强技术.对典型P2P流媒体系统的性能进行了比较,...     

无结构P2P网络中一种高效的资源搜索机制

在众多P2P资源搜索技术中,基于语义相关的搜索被重点关注。本文在基于语义分组的P2P网络拓扑下,提出了一种新颖高效的搜索方式SKIP(search with K-Iteration preference),即K-层迭代优先选择算法。查询定位到目标节点后,SKIP系统使用K-层迭代优先选择算法进行搜索。实验表明,SKIP算法具有高效的搜索效率和较低的搜索开销,与现有的基于语义的搜索策略相比,具有更高的查准率和更低的查询开销。     

WIND在P2P网络的应用

P2P应用构建的覆盖网和底层物理网络之间的不一致造成了大量的带宽浪费,WIND（World InterNet Director）是为了解决这一问题而提出的一种服务,它可以给P2P应用提供网络拓扑信息NTI（Network Topology Information）。有了NTI,P2P应用可以选择距离自己最近的用户进行连接,这样既可节省带宽也可提高系统性能。文章针对三种P2P结构：混合式、无结构、结构化P2P,提出了使WIND的方法。     

一种新的基于非结构化P2P网络的语义覆盖网络

在经典的语义覆盖网络中,所有节点都处于对等地位,没有考虑节点间共享资源数量及相对位置的差异,这使网络中节点分组信息的维护与资源搜索成本较高。丈中分析了节点间共享资源数量及相对位置的差异对语义覆盖网络中节点分组信息的维护与资源搜索代价的影响,并在此基础上提出了一种新的基于非结构化P2P网络的语义覆盖网络。该结构利用P2P网络的拓扑匹配与区分索引技术有效减少了经典语义覆盖网络中节点分组信息的维护及资源搜索代价,提升了网络的整体性能。     

一种新型的基于节点类型识别机制的P2P网络拓扑构造协议

现有P2P网络拓扑构造协议大多是基于节点历史行为来决定拓扑的构造方式,在面对P2P节点复杂多变的行为时无法实时地保证拓扑的有效性。该文首先利用博弈论针对不同类型节点的交互行为及收益建立博弈模型。在此基础上,提出了基于节点类型跟踪识别机制的拓扑构造协议TATP。仿真实验表明,TATP协议即使在恶劣的P2P网络环境下也能够让善意节点开始聚集,将恶意节点排斥到网络边缘,使得P2P网络拓扑具有更好的有效性和安全性,同时协议的网络开销较小。     

基于主题和物理位置相近原则的层次化对等语义覆盖网络结构

对等语义覆盖网络构建主要采用索引和超级节点的方法,不可避免地存在瓶颈问题,同时忽略了覆盖网络与实际网络拓扑一致性问题对语义覆盖网络性能的重要影响。该文提出的对等语义覆盖网络结构TPPH充分结合了结构化P2P网络高效的定位和非结构化P2P网络的复杂检索功能,采用分布式哈希表机制将相同主题节点组织成主题区域,在同一主题区域内通过物理位置相近原则进行群的划分,从而在物理网络拓扑基础上建立语义P2P覆盖网络结构。性能分析和仿真实验表明,该结构显著提高了查全率并缩短了平均查询时延,是一种支持复杂查询、高性能的语义覆盖网络结构。     

基于物理网络拓扑的P2P系统模型

一般的P2P系统在构建覆盖网络时。不考虑物理网络的拓扑结构，导致了较大的网络延迟。文章在Chord基础上提出了一种EChord系统模型。利用了物理网络的拓扑结构。实验结果表明EChord相比Chord不论在路由延迟还是覆盖网络的跳数上都有明显的提高。     

P2P系统中一种负载均衡的超级节点选择策略

传统的分层P2P网络拓扑构造存在超级节点服务能力偏低的问题,特别是在对时延要求高的应用中,超级节点的服务能力偏低将不能满足应用的需求。本文研究一种超级节点负载均衡的层次化网络拓扑构造方法,该方法在选择超级节点时不仅考虑节点的容量还将节点的剩余负载作为重要参考指标。在同等条件下,本方法可提高网络吞吐量,减少网络流量开销,为P2P网络的大规模应用提供了实用基础。     

P2P技术与应用浅析

P2P（Peer to Peer）技术是计算机网络中一种新兴的、重要的网络模型,是真正的并行技术、分布式技术,对互联网的广泛应用产生重要的影响。本文首先介绍了P2P技术的特点,比较了P2P技术与C／S网络模型的异同,然后详细讨论了P2P的网络拓扑结构与应用,最后总结了P2P网络的关键技术和面临的挑战。     

基于有向无环图的P2P流媒体播放系统

文中针对P2P流媒体播放中的网络拓扑构建问题,通过抽象和刻画播放节点之间的媒体同步关系,提出了基于有向无环图结构的网络拓扑构建技术。实验表明,该技术具有数据传输率高,播放延迟小等优点。基于该技术实现的P2P流媒体播放系统已经部署在Cernet2网络中。     

SKIP:an efficient search mechanism in unstructured P2P networks

Search efficiency and accuracy of resource are important considerations for search algorithm in peer-to-peer(P2P)network.Most search algorithms use flooding among neighbor nodes to search relevant resource.However,this usually causes great amount of redundant messages,which results in high search costs and low search precision.In this paper,we use vector space model(VSM)and relevance ranking algorithms to construct overlay network,and a novel search mechanism search with K-iteration preference(SKIP)based on semantic group for P2P networks is proposed to efficiently solve these problems.The key idea of SKIP is to reorder the semantic neighbors of nodes according to relevant scores and to utilize preference selection during the process of query.We analysis and implement the scheme and reveal that the SKIP provides a low overhead on topology maintenance,which can be effectively used in P2P searching and verify it outperformanee in higher precision and lower search cost by comparing with current semantic-based searching mechanism gnutella-like efficient searching system(GES).     

DynaMO: A Topology-Aware P2P Overlay Network for Dynamic,Mobile Ad-Hoc Environments

Due to the key differences between wired and ad-hoc wireless networks, traditional networking services and techniques are not always easily portable from an infrastructure based network to a wireless environment. One of the most prominent examples is the TCP transport protocol, which performs only poorly in wireless ad-hoc networks. The Peer-to-Peer (P2P) overlay networks recently developed all target the Internet where a lot of performance issues can be neglected or can be completely ignored. In addition, assumptions made for infrastructure based networks cannot be made in an ad-hoc environment, such as a fixed set of nodes which are always available. This article presents a P2P network tailored towards mobile ad-hoc environments. It utilizes proximity information to efficiently generate an overlay structure which reflects the underlying physical network topology. This way, physical routing path lengths stretched by the overlay routing process are reduced. As a novelty it does not rely on a fixed set of nodes and adapts to changes in the physical network topology. A prominent property of the overlay construction process is that the communication overhead is reduced to a minimum. Additionally, the P2P network presented maintains an even Overlay ID distribution which is deliberately given up by some solutions previously developed for wired networks. The basis of this new overlay network is Pastry, a P2P substrate based on the concept of a distributed hash table. Two different bootstrap strategies were developed and analyzed, both explicitly designed to work in dynamic and mobile networks such as ad-hoc networks.     

基于朋友相关性的P2P快速搜索算法

如何高效地搜索资源是P2P网络中最为关键的问题。对等网络拓扑结构往往不是简单的结构化或非结构化,采用单一的搜索方式效率低下,因此,提出一种改进的搜索算法——基于朋友相关性的搜索算法(FriendSearch),将基于结构化的Chord搜索算法与非结构化的洪泛搜索算法有机结合起来,在网络节点间建立朋友关系。实际系统应用表明本算法较常规Chord算法高效,准确。     

Spiralchord： a space-filling curve based location awareness, cross-layering P2P file sharing system in WMNs

The common characteristics of peer-to-peer (P2P) overlay networks and wireless multi-hop network, such as self-organization, decentralization, hop-by-hop message transmission mode and high degree of dynamicity, lead to research of operating wired P2P applications on wireless multi-hop networks. Wireless mesh network (WMN) as a relative static multi-hop wireless network which is extended from Ad-Hoc networks, has become one of the key technologies for providing increased network coverage of Internet infrastructures. This paper investigates the problem of enabling P2P file sharing in WMNs. A special chord algorithm-spiralchord is proposed to address the major problem in wireless file sharing system-how to efficiently find resources currently available. Spiralchord put forward an identifier (ID) assignment technique based on spiral space-filling curve to integrate location-awareness with cross-layering. Location awareness aims at alleviating the mismatch of physical network topology and overlay network topology, and requires close-by IDs in logical ring of neighboring peers, while cross-layering aims at speeding up resource lookup operations, requires faraway IDs of neighboring peers. Spiralchord uses spiral curve to assign peers’ IDs which meet the contradictory requirements of location-awareness and cross-layering. The simulation results show spiralchord is effective in reducing message overhead, and increasing lookup performance with respect to basic chord.     

Real-Time Streaming Relay Mechanism for P2P Conferences on Hierarchical Overlay Networks

A peer-to-peer (P2P) multimedia conferencing service is operating that users share their resources to each other on the Internet. It can solve the problem in the centralized conferencing architecture, such as the centralized loading, single point error, and expensive infrastructure. However, P2P networks have the problem that a peer has a difference between the physical location and logical location in the overlay network. In the viewpoint of P2P networks, the nearest conference resource may be far away geographically. The P2P-session initiation protocol (P2P-SIP) multimedia conference is to construct an application-based logical multicast network efficiently according to physical network information. Thus, this paper proposes a real-time streaming relay mechanism for P2P conferences on hierarchical overlay networks. The real-time streaming relay mechanism can improve the transportation efficiency of conferencing stream exchange well based on the application-layer multicast (ALM) structure and the hierarchical overlay networks.     

基于语义相似度的P2P平衡路由网络

结构化的路由算法已逐渐成为P2P的一个热点研究领域。针对目前结构化P2P算法中存在的难以有效支持基于内容的定位问题,提出了一种基于语义相似度的P2P平衡路由网络S-Tree,构造了基于平衡网络树的覆盖网络和语义拓扑。模拟实验表明,与已有的结构化P2P算法相比,S-Tree能有效提高网络的查全率,同时降低路由的延迟。