对等网中的流媒体

对等网中的流媒体是当前视频处理及通信领域的研究热点,该技术的开发和应用有着非常广阔的前景但同时也面临极大的技术挑战。本文针对对等网中的流媒体技术及其相关技术作了较为全面的介绍和分析。     

PRIME: Peer-to-Peer Receiver-Driven Mesh-Based Streaming

The success of file swarming mechanisms such as BitTorrent has motivated a new approach for scalable streaming of live content that we call mesh-based Peer-to-Peer (P2P) streaming. In this approach, participating end-systems (or peers) form a randomly connected mesh and incorporate swarming content delivery to stream live content. Despite the growing popularity of this approach, neither the fundamental design tradeoffs nor the basic performance bottlenecks in mesh-based P2P streaming are well understood.      

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流媒体关键技术研究

探讨在Peer节点服务能力的异构性、节点的动态性以及流媒体本身的特殊性下,使P2P流媒体系统保证服务质量的关键技术.从拓扑构建、调度策略、缓存机制三个方面总结P2P流媒体系统涉及的节点选择算法、节点定位方法、数据调度算法、缓存的替换和中继算法等关键技术,分析其存在的问题,指出P2P流媒体关键技术的未来研究方向,对P2P流媒体系统的研究和开发具有重要意义.     

Advances in Peer-to-Peer Streaming Systems [Guest Editorial]

The eleven papers in this special issue are devoted to advancements in peer-to-peer streaming systems.     

Deployment Issues in Scalable Island Multicast for Peer-to-Peer Streaming

The Scalable Island Multicast protocol integrates Internet Protocol multicast and overlay delivery for media streaming.     

一种改进的基于等级的P2P流媒体激励机制

P2P流媒体系统中自私节点的不合作行为严重破坏了P2P流媒体系统的整体性能.分析了Habib等人提出的基于等级的鼓励用户贡献转发资源的激励机制的缺陷,提出了一种改进的基于等级的激励机制.仿真实验结果表明,改进后的算法具有更好的性能,能更有效的抑制自私节点的行为.     

Resilience in live peer-to-peer streaming [Peer-to-Peer Multimedia Streaming]

The success of peer-to-peer overlays for live multicast streaming depends on their ability to maintain low delays and a low ratio of information loss end-to-end. However, data distribution over an overlay consisting of unreliable peers is inherently subject to disturbances. Resilience is thus inevitably a key requirement for peer-to-peer live-streaming architectures. In this article, we present a survey of the media distribution methods, overlay structures, and error-control solutions proposed for peer-to-peer live streaming. We discuss the trade off between resilience and overhead and argue that efficient architectures can be defined only through thorough performance analysis.     

VMesh: Distributed Segment Storage for Peer-to-Peer Interactive Video Streaming

Provisioning random access functions in peer-to-peer on-demand video streaming is challenging, due to not only the asynchronous user interactivity but also the unpredictability of group dynamics. In this paper, we propose VMesh, a distributed peer-to-peer video-on-demand (VoD) streaming scheme which efficiently supports random seeking functionality. In VMesh, videos are divided into segments and stored at peers' local storage in a distributed manner. An overlay mesh is built upon peers to support random forward/backward seek, pause and restart during playback. Our scheme takes advantage of the large aggregate storage capacity of peers to improve the segment supply so as to support efficient interactive commands in a scalable manner. Unlike previous work based on "cache-and-relay" mechanism, in our scheme, user interactivity such as random seeking performed by a peer does not break the connections between it and its children, and hence our scheme achieves better playback continuity. Through simulation, we show that our system achieves low startup and seeking latency under random user interactivity and peer join/leave which is a crucial requirement in an interactive VoD system.     

P2P大规模流媒体调度技术研究

随着宽带、IPV6、3G等技术的日渐成熟,流媒体应用已成为Internet承载的重要业务.调度技术是保证大规模可信流媒体服务质量的关键问题之一.对典型流媒体调度和分发技术进行综述,归纳分析了基于P2P网络环境下树型、网状以及混合拓扑结构的流媒体技术的优缺点,对mesh网下的资源发布于查找、服务节点选择、数据块调度等进行了重点分析和评述.依据流媒体应用的发展趋势,预测了P2P大规模可信流媒体调度技术在适应复杂网络,及结合云技术等方面的研究方向与内容.     

Peer-to-peer streaming for networked consumer electronics [Peer-to-Peer Multimedia Streaming]

Applications such as multimedia communications and entertainment make media streaming a key feature for peer-to-peer (P2P) technology embedded in networked consumer electronics. In this article, we discuss some key issues that are relevant to enabling peer-to-peer streaming in networked consumer electronics and address possible technical solutions to the issues of interoperability, NAT/firewall traversal, and codec inflexibility. We also address how to improve overall system performance by introducing a notion of node coordinates into the discovery of services on a P2P network and confirm the effectiveness of our approach using simulation. We conclude with a discussion of our prototype CE-oriented P2P streaming system.     

移动P2P流媒体中基于有效容量的邻居节点选择机制

For Peer-to-Peer (P2P) streaming services in mobile networks, the selection of appropriate neighbour peers from candidate peers with demanding data is an important approach to improve Quality-of-Service (QoS). This paper proposes a novel Effective Capacity Peer Se-lection (ECPS) scheme based on effective capacity. In the ECPS scheme, the neighbour peer selection problem was modeled using the Multiple Attribute Decision Making (MADM) theory, which considered multiple factors of candidate peers, including Signal to Interference and Noise Ratio (SINR), residen-cy time, power level, security, moving speed, and effective capacity. This model could increase the suitability of ECPS for wireless mobile environments. Then, the Technique for Order Preference by Similarity to Ideal Solu-tion (TOPSIS) was used to solve the MADM problem and identify the preferred neighbour peers. Simulation results show that the ECPS scheme can improve the network throughput, reduce packet delay by about 82%, and al-most double the packet delivery ratio of the mobile P2P streaming service.     

Will IPTV ride the peer-to-peer stream? [Peer-to-Peer Multimedia Streaming]

The great success of P2P systems for the purpose of file-sharing set the path to the next killer application on the Internet, P2P video streaming. Although it solves scalability issues, P2P technology experiences problems of a long start time and churn-induced instability that can greatly affect the user experience. Moreover, technical and business solutions for digital rights management are still under investigation. Great efforts are underway in both academia and industry to solve these problems, whose solution will offer a scalable, affordable, and legal TV-quality-like broadcast of content. In this article, we analyze what is available to the end user in terms of P2P video-streaming products and determine which of these are the most promising for IPTV and content distribution companies. In the following, we offer: (1) A survey of the available architectures. (2) A set of experiments on a popular peer-to-peer system, SopCast. (3) Guidelines for large scale deployment.     

支持变速率视频流传输的重协商优化算法

针对变速率视频流在多个时间尺度上突发的性质,本文提出了基于多级整形和多时间尺度带宽分配与准入的重协商优化算法.算法通过视频源与边缘网关的重协商过程,对进入网络的数据流进行包络,提高数据流的控制性和预测性,从而减少突发对网络所造成的破坏;并且对中小规模的数据流复合的情况,可以取得接近VBR流的复用增益.     

R2: Random Push with Random Network Coding in Live Peer-to-Peer Streaming

In information theory, it has been shown that network coding can effectively improve the throughput of multicast communication sessions in directed acyclic graphs. More practically, random network coding is also instrumental towards improving the downloading performance in BitTorrent-like peer-to-peer content distribution sessions. Live peer-to-peer streaming, however, poses unique challenges to the use of network coding, due to its strict timing and bandwidth constraints. In this paper, we revisit the complete spectrum in the design space of live peer-to-peer streaming protocols, with a sole objective of taking full advantage of random network coding. We present R², our new streaming algorithm designed from scratch to incorporate random network coding with a randomized push algorithm. R² is designed to improve the performance of live streaming in terms of initial buffering delays, resilience to peer dynamics, as well as reduced bandwidth costs on dedicated streaming servers, all of which are beyond the basic requirement of stable streaming playback. On an experimental testbed consisting of dozens of dual-CPU cluster servers, we thoroughly evaluate R² with an actual implementation, real network traffic, and emulated peer upload capacities, in comparisons with a typical live streaming protocol (both without and with network coding), representing the current state-of-the-art in real-world streaming applications.     

Enabling adaptive video streaming in P2P systems [Peer-to-Peer Multimedia Streaming]

Peer-to-peer (P2P) systems are becoming increasingly popular due to their ability to deliver large amounts of data at a reduced deployment cost. In addition to fostering the development of novel media applications, P2P systems also represent an interesting alternative paradigm for media streaming applications that can benefit from the inherent self organization and resource scalability available in such environments. This article presents an overview of application and network layer mechanisms that enable successful streaming frameworks in peer-to-peer systems. We describe media delivery architectures that can be deployed over P2P networks to address the specific requirements of streaming applications. In particular, we show how video-streaming applications can benefit from the diversity offered by P2P systems and implement distributed-streaming and scheduling solutions with multi-path packet transmission.     

Deploying P2P networks for large-scale live video-streaming service [Peer-to-Peer Multimedia Streaming]

Peer-to-peer (P2P) networks have been adopted for Internet live video-streaming service, and several practical systems have been deployed in past years due to the inherent scalability and ease of deployment. However, most of these systems are commercial and proprietary, and hence little research was done in the area of characterizing practical system performance properties. In this article, we mainly present our experience on a practical P2P-based live video- streaming system called GridMedia, which was employed to broadcast live the Chinese Spring Festival Gala show over the Internet. Benefiting from two sets of flush-crowd traces with about 15,239 and 224,453 concurrent users in a 300 kb/s streaming session in 2005 and 2006, we perform a trace study to understand the service capacity, quality of streaming service, connection heterogeneity, user geographic distribution, and request and online duration characteristics. Our observations shed light on those systems and further improvements in the arena of large-scale live video-streaming service over the Internet.     

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.     

基于深度报文检测和深度流检测的骨干网流量特征分析

Based on the massive data collected with a passive network monitoring equipment placed in China's backbone, we present a deep insight into the network backbone traffic and evaluate various ways for improving traffic classifying efficiency in this paper. In particular, the study has scrutinized the network traffic in terms of protocol types and signatures, flow length, and port distribution, from which meaningful and interesting insights on the current Internet of China from the perspective of both the packet and flow levels are derived. We show that the classification efficiency can be greatly improved by using the information of preferred ports of the network applications. Quantitatively, we find two traffic duration thresholds, with which 40% of TCP flows and 70% of UDP flows can be excluded from classification processing while the impact on classification accuracy is trivial, i.e., the classification accuracy can still reach a high level by saving 85% of the resources.     

Peer-to-peer live video streaming on the internet: issues, existing approaches, and challenges [Peer-to-Peer Multimedia Streaming]

Live video streaming is perhaps the greatest unfulfilled promise of the Internet. There have been tremendous efforts in the design and experimentation of video-streaming systems in the past two decades; there have been no shortage of technical innovations, yet no single system has delivered the scale and service quality. The fundamental problem that throttles the large-scale deployment of Internet video streaming is the dissatisfaction end-users experience with performance. This is caused by a combination of many factors, such as the autonomous nature of the Internet, inherent instability, and lack of a service guarantee. This is further challenged by sustainable bandwidth and the stringent continuity requirements of streaming applications. Recent development of P2P-based streaming technology brings unprecedented new momentum to Internet video streaming, which has been shown to be cost-effective, scalable, and easy to deploy. This article reviews the state-of-the-art P2P live video-streaming technologies and their development from a historic perspective. Based on our earlier success with a large-scale P2P streaming system, Coolstreaming, we summarize the main innovations and discuss the key trade offs in the system design. We present our observations on the future development and offer a few insights for further discussion.