SDHT:面向P2P直播系统的高效单跳分布式哈希查找策略

Video data location plays a key role for Peer-to-Peer (P2P) live streaming applications. In this paper, we propose a new one-hop Distributed Hash Table (DHT) lookup framework called Streaming-DHT (SDHT) to provide efficient video data location service. By adopting an enhanced events dissemination mechanism-EDRA+ , the accuracy of routing table at peers can be guaranteed. More importantly, in order to enhance the performance of video data lookup operation without incurring extra overhead, we design a so-called Distributed Index Mapping and Management Mechanism (DIMM) for SDHT. Both analytical modeling and intensive simulation experiments are conducted to demonstrate the effectiveness of SDHT framework. Numerical results show that almost 90% requested video data can be retrieved within one second in SDHT based systems, and SDHT needs only 26% average bandwidth consumption when compared with similar one-hop DHT solutions such as D1HT. This indicates that SDHT framework is an appropriate data lookup solution for time-sensitive network applications such as P2P live streaming.     

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.     

状态缓存机制在结构化P2P系统中的应用

P2P系统存在大量节点的频繁活动，导致很高的网络维护代价。文章提出了一种状态缓存机制SCM（state cache mechanism），有选择的记录和维护那些可能很快回到网络中来的离开节点的路由信息．使系统能够简化自组织性，提供高质量的路由服务。     

Inferring Network-Wide Quality in P2P Live Streaming Systems

This paper explores how to remotely monitor network-wide quality in mesh-pull P2P live streaming systems. Peers in such systems advertise to each other buffer maps which summarize the chunks of the video stream that they currently have cached and make available for sharing. We demonstrate how buffer maps can be exploited to monitor network-wide quality. We show that the information provided in a peer's advertised buffer map correlates with that peer's viewing-continuity and startup latency. Given this correlation, we remotely harvest buffer maps from many peers and then process these buffer maps to estimate the video playback quality. We apply this methodology to a popular P2P live streaming system, namely, PPLive. To harvest buffer maps, we build a buffer-map crawler and also deploy passive sniffing nodes. We process the harvested buffer maps and present results for network-wide playback continuity, startup latency, playback lags among peers, and chunk propagation patterns. The results show that this methodology can provide reasonably accurate estimates of ongoing video playback quality throughout the network.     

具有位置感知和语义特征的P2P网络模型

 非结构化P2P网络中常用的泛洪搜索方法造成了严重的通信消耗.提出一种基于位置感知和语义的P2P网络模型,在覆盖网络的构建过程中考虑底层的物理网络拓扑,同时兼顾拓扑结构与共享资源之间的相关性.该网格模型基础上,给出了语义搜索算法.实验结果表明,提出的网络模型能够减少覆盖网络与底层物理网络拓扑不匹配带来的网络开销,并且在查找性能和网络开销之间取得了良好的平衡.     

CDNPatch: a cost‐effective failover mechanism for hybrid CDN‐P2P live streaming systems

Among the most well‐established live media distribution technologies is content delivery network (CDN), which improves user‐perceived quality of service by delivering content from proxy servers deployed at the Internet's edge. In recent years, CDN providers started to tap into their subscribers' peer‐to‐peer (P2P) capacity to alleviate their server costs. Under the inherent peer dynamics, a major challenge of these hybrid CDN‐P2P systems is to provide efficient failure recovery with good quality of service guarantees at a reduced server cost. In this work we propose a cost‐effective failover solution named CDNPatch to address the aforementioned problem. CDNPatch enables peers to periodically precompute a few backup content suppliers by efficient information exchange and maintenance algorithms, and leverages auxiliary CDN servers and an economic server provisioning algorithm to reduce the chance of playback interruption occurring to peers. Our simulation results show that CDNPatch can mask the impact of peer dynamics of 3 real P2P systems, namely, SOPCast, PPStream, and PPTV, with 100 % failure recovery success rate and a failure recovery time less than 1 second at a cost of small P2P communication overhead of less than 1 kilobits per second, while using only 10%, 21%, and 51%, respectively, of the pure CDN scheme's server consumption.     

Reliability-oriented ant colony optimization-based mobile peer-to-peer VoD solution in MANETs

Mobile peer-to-peer (MP2P) has emerged as a state-of-the-art technology for video resource sharing in mobile ad-hoc networks (MANETs), building on the advantages of P2P data exchange and providing a feasible solution for large-scale deployment of media streaming services. Fast search for video resources and low maintenance overhead of overlay networks to support the mobility of nodes are key factors in MP2P video on demand solutions. In this paper, we propose a novel reliability-oriented ant colony optimization (ACO)-based MP2P solution to support interactivity for video streaming in MANETs (RACOM). RACOM makes use of highly innovative algorithms such as the peer status-aware mechanism and peer-centric overlay maintenance mechanism to support high-efficiency video resource sharing. The peer status-aware mechanism includes the user reliability measure model which is used to identify the peers having reliable playback status in order to find stable potential resource suppliers and a new ACO-based prediction model of playback behavior which provides the accurate prediction of playback content in the future to ensure the smooth experience and optimize the distribution of resources. In order to balance the fast supplier discovery and low maintenance overhead, RACOM makes use of peer-centric overlay maintenance mechanism composed of the time window-based detection strategy and encounter-based synchronization strategy to reduce the maintenance overhead of reliable peers, obtain quasi real-time status of peers and support the mobility of mobile nodes. Simulation results show how RACOM achieves higher hit ratio, lower seek delay, lower server stress, lower peer load and less overlay maintenance overhead in comparison with another state of the art solution.     

GigaManP2P: an overlay network for distributed QoS management and resilient routing

Management of long‐distance, high‐speed optical backbones spanning multiple administrative domains requires new solutions for challenging tasks. In particular, it is not trivial to negotiate, monitor and continuously enforce the required quality of service (QoS) for applications that span multiple domains. This paper proposes GigaManP2P: a novel peer‐to‐peer (P2P) management architecture for high‐speed QoS‐aware backbones. GigaManP2P peers provide management services in a ubiquitous fashion through modules that interface with both the communication infrastructure and network users. In particular, we describe management services for on inter‐domain QoS monitoring and resilient routing. After detecting a QoS constraint violation trend, a proactive rerouting strategy is triggered based on redundant virtual circuits, allowing both full and partial rerouting. The P2P overlay implementation is the basis for allowing transparent communication across autonomous systems. Experimental results showing the overhead of the P2P infrastructure in comparison to raw Simple Network Management Protocol, and the performance of the rerouting strategy, are presented. Copyright © 2011 John Wiley & Sons, Ltd.     

CAR：一种MANET环境下的P2P资源定位与获取算法

针对移动自组网(MANET)环境的特殊性,引用DHT思想,设计了一种适于MANET环境的基于地理位置信息的分层散列索引结构GH2I。基于该结构,设计了一种移动对等(MP2P)覆盖网络资源定位与获取算法CAR。从而实现一种MANET环境下的具有较好可扩展性、资源查找与获取高效性以及移动环境适应性的MP2P网络。     

Residual-Based Estimation of Peer and Link Lifetimes in P2P Networks

Existing methods of measuring lifetimes in P2P systems usually rely on the so-called Create-Based Method (CBM), which divides a given observation window into two halves and samples users ldquocreatedrdquo in the first half every Delta time units until they die or the observation period ends. Despite its frequent use, this approach has no rigorous accuracy or overhead analysis in the literature. To shed more light on its performance, we first derive a model for CBM and show that small window size or large Delta may lead to highly inaccurate lifetime distributions. We then show that create-based sampling exhibits an inherent tradeoff between overhead and accuracy, which does not allow any fundamental improvement to the method. Instead, we propose a completely different approach for sampling user dynamics that keeps track of only residual lifetimes of peers and uses a simple renewal-process model to recover the actual lifetimes from the observed residuals. Our analysis indicates that for reasonably large systems, the proposed method can reduce bandwidth consumption by several orders of magnitude compared to prior approaches while simultaneously achieving higher accuracy. We finish the paper by implementing a two-tier Gnutella network crawler equipped with the proposed sampling method and obtain the distribution of ultrapeer lifetimes in a network of 6.4 million users and 60 million links. Our experimental results show that ultrapeer lifetimes are Pareto with shape alpha ap 1.1; however, link lifetimes exhibit much lighter tails with alpha ap 1.8.