P4P：P2P的替代者

P2P网络的出现,成功地实现了可扩展的网络应用设计,并且已经成为一种新的范式。然而,P2P也面临着如何高效和公平地利用网络资源的挑战。特别是,缺乏明确地与网络供应商进行沟通,P2P的应用程序可能会消耗太多的带宽,使网络运营商负担不起,导致供应商采取很多限制P2P的措施。文章提出了一个简单,轻量的P4P结构,以便更有效地与网络供应商合作,最终更加高效地利用网络资源。     

由P2P技术展望P4P

P2P技术在短短几年之内经历了从初生到成熟再到大规模普及的飞速发展,其为广大互联网网民带来了极为丰富的资源和高速的体验,然而面对P2P带来的侵犯版权、信誉以及隐私保护等问题,P4P技术的出现似乎带来一些生机。本文从当前P2P技术的基本情况、面临难题谈起,介绍了P4P技术的原理,并对其发展前景做了展望。     

P2P技术

本文简要介绍了P2P技术的实现原理.文章以对SKYPE软件进行黑盒分析的结果为基础,深入剖析了SKYPE的实现技术,包括网络结构、呼叫接续、被叫寻址以及语音编码等各方面.对研究P2P语音技术的人员有一定的参考价值.     

P2P运营模式及P2P业务发展策略

目前主要P2P业务的运营模式主要有:Skype模式、广告模式、商贩模式、网格计算模式、电子商务模式。这些业务运营模式可以降低应用提供门槛,实现系统自激励机制,实现资费分担,增加用户"黏"度。未来,P2P的一个可能的方向是平台化,即形成一个基于P2P的资源交换平台,这个平台对用户进行抽象,对资源进行统一建模,并以一致的方式进行资源标识、注册、索引和搜索。用户之间的交互协议,可以采用标准的会话初始化协议(SIP)方式进行,实现标准化。交互接口可以按照可扩展标记语言(XML)的方式进行定义。不同的应用将基于这个平台构建不同的资源交换模型,并生成不同的应用逻辑。     

P2P参考模型研究

The security of critical data is an important issue for distributed storage system design, especially for long-term storage. ESSA (An Efficient and Secure Splitting Algorithm for Distributed Storage Systems) is presented, which takes advantage of a two level information dispersal scheme to strengthen the security of data. In ESSA, the approach of knight’s tour problem, which is NP-Complete, is introduced to scramble data at the first level, and a split cube is used to split scrambled data at the second level. Thus, it is very difficult for the malicious user to get information because the task of reconstructing the original data needs more computation than they can tolerate. We prove that the security of ESSA is better than encryption algorithm and not inferior to erasure codes and secret sharing. Experimental results show that distributed storage systems exploiting ESSA has greater efficiency than that exploiting keyed encryption, erasure codes and
secret sharing     

P2P仿真综述

随着P2P技术的飞速发展,出现了大量的P2P算法和协议,验证算法正确性和评价P2P系统性能的需求推动了P2P模拟器的发展.现详细介绍了几种常用的P2P模拟器,对其优缺点进行了评价.     

P2P与IPTV

目前,多数IPTV网络采用CDN作为支撑,即将内容根据需要传递到一个或一批用户端。CDN不仅可以完成对多媒体内容的存储、调度、转发、播放等,还可以降低服务器和带宽资源的消耗并提高服务质量。由于现有的CDN是从基于PC的流媒体业务发展而来的,在多个用户同时选择吲一内容时存在服务效率低、重定向机制复杂等问题,因此它对直播电视、时延电视等增值业务的支持能力有限。     

P2P流媒体技术

P2P技术是一种打破了传统的Client／Server模式，基于对等节点非中心化服务的平台方案。其“去中心化特点符合WEB2．0技术潮流，特别在流媒体领域，由于采用Peer之间对等计算的模式，大大提高了资源共享的利用率，能在较低的成本下，充分利用空闲时间分发数据，避免拥塞，提供具备高实时性、容错性能的流服务，为流媒体开辟了一条崭新的道路。     

P to P和软交换

电话网发展的第一阶段是逐步过渡到以软交换为核心的网络,但软交换在许多地方沿用了电话网的思路,并不是纯粹以IP为基础通信网的最佳选择。它作为电话网向IP网演进的权宜之计和过渡方案而登场,但是IP网的无连接特性和开放性注定了软交换的作用将是昙花一现的;未来发展的趋势是网络将趋于简单,而终端将越来越复杂,功能越来越强大;在电话网发展的第二阶段,在纯IP的环境中具有更高效率的通信模式,将会成为通信的主流。     

Robust mobile video streaming in a peer-to-peer system

In a peer-to-peer (P2P) video streaming system, peers not only consume video, but also route it to other peers in the system, where ordinary peers are assumed to have sufficient downlink speed and media capability. This assumption often fails when the P2P system consists of peers that are heterogeneous in their computing power, hardware, and media capability.In this paper, we address a problem of streaming video to mobile devices, which are less capable than ordinary peers. In order to stream video to mobile devices, transcoding is often required to render video suitable for their small display, limited downlink speed, and limited video decoding capability. However, performing transcoding at a single peer is vulnerable to peer churn, which leads to video disruption. We propose interleaved distributed transcoding (IDT), a robust video encoding scheme that allows peers more capable than mobile devices to perform transcoding in a collaborative fashion. IDT is designed in such a way that transcoded substreams are assembled into a single video stream, which can be decoded by any H.264/AVC baseline profile compliant decoder. Extensive simulations and its implementation in a real P2P system demonstrate that the proposed scheme not only reduces computational load at a peer, but also achieves robust streaming in the case of peer failure or packet loss due to adverse wireless channel conditions. We confirm this finding by analyzing the effect of distributed transcoding under peer failure.     

Evolved data scheduling scheme based on layered P2P streaming in mobile network

To relieve the negative effect brought by the intricate wireless network environment and unstable user behavior in layered mobile peer-to peer(P2P) streaming service,an evolved layered P2P (E-LP2P) dat...     

分层P2P实时流媒体系统中基于演进博弈的超级组对等节点选择算法

针对分层混合式P2P实时流媒体系统中的超级组对等节点选择问题,提出了以一种基于演进博弈论的分布式超级对等节点选择算法。首先使用演进博弈框架对P2P实时流媒体系统中的超级对等节点选择问题进行了建模,并对其演进稳定策略进行了求解分析。然后通过得到的混合策略设计了一种基于Q-Leaning的分布式SGP选择算法ESS-SGP,以达到激励对等组内的对等节点之间互相协作的目的。实验结果表明,与传统的随机选择超级对等节点方法相比,使用ESS-SGP算法所选择产生的超级组对等节点能够稳定地为系统提供更高的流媒体上传速率,使整个P2P流媒体系统的上传能力随着对等节点数目的增加而稳定增加,并为每个对等节点带来更好的收益。     

一种可控对等网络流媒体直播系统

在基于随机覆盖拓扑的对等网络直播系统中,全分布式资源定位和数据传输难以有效利用网络资源和提高直播应用性能。本文提出一种可控对等网络直播系统,其采用集中与分布相结合的方式和地域优先策略实现资源节点的有效定位,通过引入服务器补偿传输策略解决ADSL接入链路上载带宽不足问题和提高直播应用性能,数据传输采用改进的推拉结合方式。仿真分析表明,本文系统在播放连续度、启动播放时延和流量负载等方面均优于CoolStreaming。     

P2P流媒体技术原理及应用

基于P2P的流媒体技术是一项非常有前途的技术,该技术有两方面的优点:不需要互联网路由器和网络基础设施的支持,因此性价比高且易于部署;流媒体用户不只是下载媒体流,而且还把媒体流上载给其他用户,因此,这种方法可以扩大用户组的规模,且由更多的需求带来更多的资源。由于P2P流媒体系统中节点存在不稳定性,因此P2P流媒体系统需要在文件定位技术、节点选择技术、容错以及安全机制方面有所突破。此外在如何管理节点并建立发布树、如何应付不可预知的节点失效、如何适应网络状态变化方面也面临着一些挑战。     

P2P流媒体中的多发送端选择算法

 在多对单P2P流模式下,如何选择多个发送端,并为其最优地分配发送速率和数据是一个难题.为此,提出了一种新的多发送端选择和最优速率及数据分配算法(MSRDA).首先把待解决的问题模型化为线性最优化问题,然后给出了求解最优化问题的算法.不同于已有的算法只按链路的丢包率来选择发送端,MSRDA根据到各发送端链路的丢包率与链路的可用带宽比升序排序来选择多发送端,并最优地分配发送速率和数据.理论分析和仿真实验结果表明:在不同的网络条件下MSRDA能有效地减少聚合带宽的丢包率,并具有自适应性,优于现有同类算法.     

Network-aware P2P file sharing over the wireless mobile networks

With the coming wireless mobile networks era and the popular use of P2P applications, how to improve the resource retrieval and discovery for P2P file sharing applications in wireless mobile networks becomes a critical issue. In this paper, we propose a novel network-aware P2P file architecture and related control schemes that can provide continuous resource retrieval and discovery for mobile users over the wireless network environment. The proposed architecture divides a P2P file sharing network into multiple network-aware clusters, in which peers are assigned to a network-aware cluster using a network prefix division. Accordingly, there are two designs for supporting mobile peers to retrieve files in wireless mobile networks. First, a novel file discovery control scheme named mobility-aware file discovery control (MAFDC) scheme is devised to obtain fresh status of shared peers and find the new resource providing peers in wireless mobile networks. Second, a resource provider selection algorithm is devised to enable a mobile peer to select new resource providing peers for continuous file retrieval     

Modeling and application of moderate prefetching strategy based on video slicing for P2P VoD systems

In peer-to-peer (P2P) video-on-demand (VoD) streaming systems,each peer contributes a fixed amount of hard disk storage (usually 2 GB) to store viewed videos and then uploads them to other requesting p...     

基于联合调度和DHT补偿的P2P直播系统播放质量改善策略

In Peer-to-Peer (P2P) streaming systems, video data may be lost since peers can join and leave the overlay network randomly, thereby deteriorating the video playback quality. In this paper we propose a new hybrid mesh and Distributed Hash Table (DHT) based P2P streaming system, called HQMedia, to provide high playback quality to users by maintaining high data dissemination resilience with a low overhead. In HQMedia, peers are classified into Super Peers (SP) and Common Peers (CP) according to their online time. SPs and CPs form a mesh structure, while SPs alone form a new Streaming DHT (SDHT) structure. In this hybrid architecture, we propose a joint sched-uling and compensation mechanism. If any frames cannot be obtained during the scheduling phase, an SDHT-based compensation mechanism is invoked for retrieving the missing frames near the playback point. We evaluate the performance of HQMedia by both theoretical analysis and intensive simulation experiments on large-scale networks to demonstrate the ef-fectiveness and scalability of the proposed system. Numerical results show that HQMedia significantly outperforms existing mesh-based and treebased P2P live streaming systems by improving playback quality with only less than 1% extra maintenance overhead.