Due to the explosive growth of the Internet and increasing demand for multimedia information on the Web, streaming video over the Internet has received tremendous attention from academia and industry. Transmission of real-time video typically has bandwidth, delay, and loss requirements. However, the current best-effort Internet does not offer any quality of service (QoS) guarantees to streaming video. Furthermore, for video multicast, it is difficult to achieve both efficiency and flexibility. Thus, Internet streaming video poses many challenges. In this article we cover six key areas of streaming video. Specifically, we cover video compression, application-layer QoS control, continuous media distribution services, streaming servers, media synchronization mechanisms, and protocols for streaming media. For each area, we address the particular issues and review major approaches and mechanisms. We also discuss the tradeoffs of the approaches and point out future research directions.

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Streaming video over the Internet: approaches and directions

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.

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Proxy caching for media streaming over the Internet

For over two decades, video streaming over the Internet has received a substantial amount of attention from both academia and industry. Starting from the design of transport protocols for streaming video, research interests have later shifted to the peer-to-peer paradigm of designing streaming protocols at the application layer. More recent research has focused on building more practical and scalable systems, using Dynamic Adaptive Streaming over HTTP. In this article, we provide a retrospective view of the research results over the past two decades, with a focus on peer-to-peer streaming protocols and the effects of cloud computing and social media.

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Two decades of internet video streaming: A retrospective view

This paper presents a scheduling model for a class of interactive services in which requests are time bounded and lower result quality can be traded for shorter execution time. These applications include web search engines, finance servers, and other interactive, on-line services. We develop an efficient scheduling algorithm, Zeta, that allocates processor time among service requests to maximize the quality and minimize the variance of the response.Zeta exploits the concavity of the request quality profile to distribute processing time among outstanding requests. By executing some requests partially (and obtaining much or most benefit of a full execution), Zeta frees resources for other requests, which might have timed out and produced no results. Compared to scheduling algorithms that consider only deadline or quality profile information, Zeta improves overall response quality and reduces response quality variance, yielding significant improvement in the high-percentile response quality.We implemented and deployed Zeta in the Microsoft Bing web search engine and evaluated its performance in a production environment with realistic workloads. Measurements show that at the same response quality and latency as the production system, Zeta increases system capacity by 29% by improving both average and high percentile response quality. We also implemented Zeta in a finance server that computes option prices. In this application, Zeta improves average response quality by 28% and the 99-percentile quality by 80%. Using a simulation, we also compared Zeta to the offline optimal schedule and other scheduling algorithms. Although Zeta is only close to optimal, it provides better performance than prior algorithms under a wide variety of operating conditions.

Zeta: scheduling interactive services with partial execution

Delivering multimedia over wireless Internet is a very challenging task. Multimedia delivery inherently has strict quality-of-service (QoS) requirement on bandwidth, delay, and delay jitter. However, the current Internet can only support best-effort service, which imposes varying network conditions during multimedia delivery. The advent of wireless networks further exacerbates the variance of network conditions and brings greater challenges for multimedia delivery. To improve perceived media quality by end users over wireless Internet, QoS supports can be addressed in different layers, including application layer, transport layer, link layer, and so forth. This paper presents a framework, which provides QoS support, for multimedia delivery over wireless Internet, across different layers. To provide efficient QoS support for different types of media over the best-effort networks, we first propose a cross-layer architecture, which combines the application-level, transport-layer, as well as link-layer controls, and then review recent advances in each individual component. Specifically, dynamic estimation of varying channel and network, adaptive and energy-efficient application and link-level error control, efficient congestion control, header compression, adaptive automatic repeat request (ARQ) and priority-based scheduling, as well as QoS-adaptive proxy caching technologies are explicitly reviewed in this paper.

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Cross-layer QoS support for multimedia delivery over wireless internet

QoS-adpative proxy caching for multimedia streaming over the Internet

This paper proposes a quality-of-service (QoS)-adaptive proxy-caching scheme for multimedia streaming over the Internet. Considering the heterogeneous network conditions and media characteristics, we present an end-to-end caching architecture for multimedia streaming. First, a media-characteristic-weighted replacement policy is proposed to improve the cache hit ratio of mixed media including continuous and noncontinuous media. Secondly, a network-condition- and media-quality-adaptive resource-management mechanism is introduced to dynamically re-allocate cache resource for different types of media according to their request patterns. Thirdly, a pre-fetching scheme is described based on the estimated network bandwidth, and a miss strategy to decide what to request from the server in case of cache miss based on real-time network conditions is presented. Lastly, request and send-back scheduling algorithms, integrating with unequal loss protection (ULP), are proposed to dynamically allocate network resource among different types of media. Simulation results demonstrate effectiveness of our proposed schemes.

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QoS-adaptive proxy caching for multimedia streaming over the Internet

For efficently caching mixed-media, this paper discusses several network-adaptive cache management schemes. Considering the characteristics of different types of media, we first proposed a multi-level page-size management scheme. Then, a media-characteristic-weighted replacement policy is presented to improve the hit ratio of mixed media including continuous and noncontinuous media. Lastly, a network-condition- and media-quality-adaptive resource management mechanism is described to dynamically re-allocate cache resource for different types of media according to their request patterns. Simulation results demonstrate effectiveness of our propsoed approaches.

Fang Yu

Papers

QoS-adpative proxy caching for multimedia streaming over the Internet

QoS-adaptive proxy caching for multimedia streaming over the Internet

Network-Adaptive Cache Management Schemes for Mixed Media