基于段流行度的移动流媒体代理服务器缓存算法

提出了一种基于段流行度的移动流媒体代理服务器缓存算法P2CAS2M2(proxy caching algorithm based on segment popularity for mobile streaming media),根据移动流媒体对象段的流行度,实现了代理服务器缓存的接纳和替换,使移动流媒体对象在代理服务器中缓存的数据量和其流行度成正比,并且根据客户平均访问时间动态决定该对象缓存窗口大小。仿真结果表明,对于代理服务器缓存大小的变化,P2CAS2M2比A2LS(adaptive and lazy segmentation algorithm)具有更好的适应性,在缓存空间相同的情况下,能够得到更大的被缓存流媒体对象的平均数,更小的被延迟的初始请求率,降低了启动延时,而字节命中率接近甚至超过A2LS。     

Cache Optimization on Hot‐Point Proxy Caching Using Weighted‐Rank Cache Replacement Policy

The development of proxy caching is essential in the area of video‐on‐demand (VoD) to meet users' expectations. VoD requires high bandwidth and creates high traffic due to the nature of media. Many researchers have developed proxy caching models to reduce bandwidth consumption and traffic. Proxy caching keeps part of a media object to meet the viewing expectations of users without delay and provides interactive playback. If the caching is done continuously, the entire cache space will be exhausted at one stage. Hence, the proxy server must apply cache replacement policies to replace existing objects and allocate the cache space for the incoming objects. Researchers have developed many cache replacement policies by considering several parameters, such as recency, access frequency, cost of retrieval, and size of the object. In this paper, the Weighted‐Rank Cache replacement Policy (WRCP) is proposed. This policy uses such parameters as access frequency, aging, and mean access gap ratio and such functions as size and cost of retrieval. The WRCP applies our previously developed proxy caching model, Hot‐Point Proxy, at four levels of replacement, depending on the cache requirement. Simulation results show that the WRCP outperforms our earlier model, the Dual Cache Replacement Policy.     

Efficient web content delivery using proxy caching techniques

Web caching technology has been widely used to improve the performance of the Web infrastructure and reduce user-perceived network latencies. Proxy caching is a major Web caching technique that attempts to serve user Web requests from one or a network of proxies located between the end user and Web servers hosting the original copies of the requested objects. This paper surveys the main technical aspects of proxy caching and discusses recent developments in proxy caching research including caching the "uncacheable" and multimedia streaming objects, and various adaptive and integrated caching approaches.     

Considering User Behavior and Multiple QoS Supports in Multimedia Streaming Caching

With the prevalence of video-on-demand (VOD) services as well as the diffusion of various multimedia devices, caching in a multimedia streaming server is becoming increasingly important. However, due to some peculiar characteristics of multimedia objects and user activities in streaming services, design of an efficient caching system becomes a more challenging problem compared to the traditional caching systems. This paper discusses some important issues that are of interest in the domain of multimedia streaming caching and presents a new cache management scheme for multimedia streaming servers. Our new scheme considers different streaming rates of multimedia objects as well as the inter-arrival time between two consecutive requests on an identical object. It also considers user activities in requesting and playing multimedia contents. Trace-driven simulations with real world VOD traces show that the proposed scheme improves the performance of multimedia streaming systems significantly.     

Proxy-assisted techniques for delivering continuous multimedia streams

We present a proxy-assisted video delivery architecture that can simultaneously reduce the resources requirements at the central server and the service latency experienced by clients (i.e., end users). Under the proposed video delivery architecture, we develop and analyze two novel proxy-assisted video streaming techniques for on-demand delivery of video objects to a large number of clients. By taking advantage of the resources available at the proxy servers, these techniques not only significantly reduce the central server and network resource requirements, but are also capable of providing near-instantaneous service to a large number of clients. We optimize the performance of our video streaming architecture by carefully selecting video delivery techniques for videos of various popularity and intelligently allocating resources between proxy servers and the central server. Through empirical studies, we demonstrate the efficacy of the proposed proxy-assisted video streaming techniques.     

An empirical study on user access to entertainment streaming media

I. Introduction Streaming media has been widely used over the Internet in recent years. However, the growing use in streaming media, which generally has large size, can have a significant impact on the user perceived latency and network congestion. A popular approach to reduce the response time and backbone bandwidth consumption is to deploy proxy caches at the edge of the Internet. Due to the large size and different popularity for different part of the streaming video, it is not practical …     

Scalable proxy caching of video under storage constraints

Proxy caching has been used to speed up Web browsing and reduce networking costs. In this paper, we study the extension of proxy caching techniques to streaming video applications. A trivial extension consists of storing complete video sequences in the cache. However, this may not be applicable in situations where the video objects are very large and proxy cache space is limited. We show that the approaches proposed in this paper (referred to as selective caching), where only a few frames are cached, can also contribute to significant improvements in the overall performance. In particular, we discuss two network environments for streaming video, namely, quality-of-service (QoS) networks and best-effort networks (Internet). For QoS networks, the video caching goal is to reduce the network bandwidth costs; for best-effort networks, the goal is to increase the robustness of continuous playback against poor network conditions (such as congestion, delay, and loss). Two different selective caching algorithms (SCQ and SCB) are proposed, one for each network scenario, to increase the relevant overall performance metric in each case, while requiring only a fraction of the video stream to be cached. The main contribution of our work is to provide algorithms that are efficient even when the buffer memory available at the client is limited. These algorithms are also scalable so that when changes in the environment occur it is possible, with low complexity, to modify the allocation of cache space to different video sequences.     

Segment-based proxy caching for Internet streaming media delivery

The proliferation of multimedia content on the Internet poses challenges to existing content delivery networks. While proxy caching can successfully deliver traditional text-based static objects, it faces difficulty delivering streaming media objects because of the objects' sizes as well as clients' rigorous continuous delivery demands. We present two techniques supporting segment based proxy caching of streaming media. We evaluated these techniques in simulations and real systems.     

Partial video sequence caching scheme for VOD systems withheterogeneous clients

Video on demand (VOD) is one of the key applications in the information era. A hinge factor to its widespread use is the huge bandwidth required to transmit digitized video to a large group of clients with widely varying requirements. This paper addresses issues of heterogeneous clients by proposing a program caching scheme called the partial video sequence (PVS) caching scheme. The PVS caching scheme decomposes video sequences into a number of parts by using a scalable video compression algorithm. Video parts are selected to be cached in local video servers based on the amount of bandwidth that would be demanded from the distribution network and central video server if it was only kept in the central video server. We also show that the PVS caching scheme is suitable for handling vastly varying client requirements     

Video staging: a proxy-server-based approach to end-to-end videodelivery over wide-area networks

Real-time distribution of stored video over wide-area networks (WANs) is a crucial component of many emerging distributed multimedia applications. The heterogeneity in the underlying network environments is an important factor that must be taken into consideration when designing an end-to-end video delivery system. We present a novel approach to the problem of end-to-end video delivery over WANs using proxy servers situated between local-area networks (LANs) and a backbone WAN. A major objective of our approach is to reduce the backbone WAN bandwidth requirement. Toward this end, we develop an effective video delivery technique called video staging via intelligent utilization of the disk bandwidth and storage space available at proxy servers. Using this video staging technique, only part of a video stream is retrieved directly from the central video server across the backbone WAN whereas the rest of the video stream is delivered to users locally from proxy servers attached to the LANs. In this manner, the WAN bandwidth requirement can be significantly reduced, particularly when a large number of users from the same LAN access the video data. We design several video staging methods and evaluate their effectiveness in trading the disk bandwidth of a proxy server for the backbone WAN bandwidth. We also develop two heuristic algorithms to solve the problem of designing a multiple video staging scheme for a proxy server with a given video access profile of a LAN. Our results demonstrate that the proposed proxy-server-based approach provides an effective and scalable solution to the problem of the end-to-end video delivery over WANs     

Proxy caching for media streaming over the Internet

Streaming media has contributed to a significant amount of today's Internet traffic. Like conventional Web objects (e.g., HTML pages and images), media objects can benefit from proxy caching; but their unique features such as huge size and high bandwidth demand imply that conventional proxy caching strategies have to be substantially revised. This article discusses the critical issues and challenges of cache management for proxy-assisted media streaming. We survey, classify, and compare the state-of-the-art solutions. We also investigate advanced issues of combining multicast with caching, cooperating among proxies, and leveraging proxy caching in overlay networks.     

Video delivery technologies for large-scale deployment of multimedia applications

Deployment of a large-scale multimedia streaming application requires an enormous amount of server and network resources. The simplest delivery technique allocates server resources for each specific request. This technique is very expensive and is not scalable to support a very large user community such as the Internet. Hence, the past decade has witnessed tremendous research efforts to facilitate cost-effective, large-scale deployment of multimedia streaming applications. In this paper, we describe three complementary research approaches: server transmission schemes using multicast, streaming strategies with application layer multicast, and proxy caching techniques. We discuss pros and cons of these technologies and provide our observations on current business solutions.     

基于Linux的Squid代理系统的研究和实现

Squid是Linux平台下流行的高性能应用层代理服务器软件,常用于搭建代理服务器或者网页服务器的前置缓存服务器。文中主要介绍了在Linux系统下使用Squid建立代理服务器,通过缓存、访问控制等机制来实现高效、安全、低成本的代理服务。在此基础上,结合企业具体情况,研究实现了多级架构、双机互备、访问日志分析等功能。最后对代理加速、反向代理在企业的应用实现进行了展望。     

Traffic Modeling and Proportional Partial Caching for Peer-to-Peer Systems

Peer-to-peer (P2P) file sharing systems generate a major portion of the Internet traffic, and this portion is expected to increase in the future. We explore the potential of deploying proxy caches in different Autonomous Systems (ASes) with the goal of reducing the cost incurred by Internet service providers and alleviating the load on the Internet backbone. We conduct an eight-month measurement study to analyze the P2P traffic characteristics that are relevant to caching, such as object popularity, popularity dynamics, and object size. Our study shows that the popularity of P2P objects can be modeled by a Mandelbrot–Zipf distribution, and that several workloads exist in P2P traffic. Guided by our findings, we develop a novel caching algorithm for P2P traffic that is based on object segmentation, and proportional partial admission and eviction of objects. Our trace-based simulations show that with a relatively small cache size, a byte hit rate of up to 35% can be achieved by our algorithm, which is close to the byte hit rate achieved by an off-line optimal algorithm with complete knowledge of future requests. Our results also show that our algorithm achieves a byte hit rate that is at least 40% more, and at most triple, the byte hit rate of the common web caching algorithms. Furthermore, our algorithm is robust in face of aborted downloads, which is a common case in P2P systems.      

针对移动视频终端的基于感兴趣区域的快速转换编码

提出一种针对移动终端,基于感兴趣区域(ROI)的快速转换编码方案.首先,根据移动终端的显示尺寸,在视频服务器端利用视觉关注度模型从H.264视频流自动地检测出ROI.然后,在代理服务器端根据ROI转换编码生成适合于移动终端的视频流.此外,针对此转码体系提出了一种快速模式选择算法.仿真实验结果表明,本方案可在降低网络占用带宽的情况下,获得较好的主观视觉效果,并且计算量小.     

A dynamic quality of service framework for video in broadbandnetworks

A dynamic framework for QoS control of video in distributed multimedia applications is presented. The framework allows flexible and efficient video delivery with application-level QoS support. Key components of the framework are client QoS renegotiation, server source rate control, and dynamic bandwidth allocation. The coordinated functionality of these distributed components provides soft QoS to adaptive applications. A proof-of-concept prototype of a video browser with user-level control of soft QoS is implemented within the proposed framework. The implementation uses a distributed software architecture that represents soft QoS requirements by software objects called service contracts. These objects are exchanged among servers, network nodes, and clients to achieve distributed soft QoS control. Experiences with the prototype and its performance are discussed     

Hierarchical storage management in a distributed VOD system

The article describes the storage management algorithms in the Berkeley Video-on-Demand System, a hierarchical storage management system designed to support transparent access to thousands of hours of video material. Storage management algorithms handle continuous media objects stored on video servers within a hierarchical distributed video-on-demand system. Media objects stored permanently on tertiary storage devices are moved to video servers when needed. Algorithms manage the distributed cache in the video servers and select a video server on which to place a requested object. The object-placement algorithm uses server load, network load, and service-wait times to optimize system performance     

Optimal multicast smoothing of streaming video over the Internet

A set of applications such as Internet video broadcasts, corporate telecasts, and distance learning require the simultaneous streaming of video to a large population of viewers across the Internet. The high bandwidth requirements and the multi-timescale burstiness of compressed video make it a challenging problem to provision network resources for streaming multimedia. For such applications to become affordable and ubiquitous, it is necessary to develop scalable techniques to efficiently stream video to a large number of disparate clients across a heterogeneous Internet. In this paper, we propose to multicast smoothed video over an application-level overlay network of proxies, and to differentially cache the video at the intermediate nodes (proxies) in the distribution tree, in order to reduce the network bandwidth requirements of video dissemination. We formulate the multicast smoothing problem as an optimization problem, and develop an algorithm for computing the set of transmission schedules for the tree that minimize the peak rate and rate variability, given buffer constraints at different nodes in the tree. We also develop an algorithm to compute the minimum buffer allocation in the entire tree, such that feasible transmission to all the clients is possible, when the tree has heterogeneous rate constraints. We show through trace-driven simulations that substantial benefits are possible from multicast smoothing and differential caching, and that these gains can be realized even with modest proxy caches.     

基于网络代价的流媒体缓存策略研究

该文构造了一种新的流媒体缓存效用函数,该函数综合考虑流媒体节目的流行度特性及传输网络的代价参数;设计了一种针对多视频服务器、基于网络代价的流媒体缓存分配与替换算法(Network Cost Based cache allocation and replacement algorithm, NCB)。仿真实验结果显示,NCB算法有效提高了缓存命中率,降低了传送流媒体所消耗的总体网络代价;该算法在网络结构复杂、节目数量庞大的Internet流媒体应用环境中表现出较优越的性能。     

QoE‐based pseudo heartbeat message compression mechanism for future wireless network

Wireless multimedia services are increasingly becoming popular, which boosts the need for better quality‐of‐experience (QoE). However, there are many aspects leading to the degradation of real‐time video QoE, especially, a large number of always‐on‐line (AOL) applications existing in future wireless networks transmit heartbeat message periodically to keep always‐on, and hence induce heavy signaling costs and overload wireless networks. In this paper, we propose QoE‐based pseudo heartbeat message compression mechanism to reduce the number of signaling loads in the radio access network by intercepting the heartbeat message at a certain frequency in the proxy client. To maintain the protocol feature of the AOL applications, the heartbeat messages are reconstructed by the proxy server and sent to the application server. Furthermore, to analyze the influence of this mechanism on the video user, a new QoE perception model is proposed. Finally, combined the QoE perception model for video services with AOL services, the utility function for joint optimization multi‐services is developed to determine the optimum compression frequency. The simulation results show that the proposed mechanism greatly alleviates the signaling load and leads to a significant performance improvement on the QoE of video users, while a slight decrease in the QoE of AOL users. Copyright © 2016 John Wiley & Sons, Ltd.