Dongli Su

Bio: Dongli Su is an academic researcher from University of Minnesota. The author has contributed to research in topics: Local area network & Bandwidth (computing). The author has an hindex of 2, co-authored 3 publications receiving 337 citations.

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

Abstract: 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.

A network-conscious approach to end-to-end video delivery over wide area networks using proxy servers

Abstract: In this paper we present a novel network-conscious approach to the problem of end-to-end video delivery over wide-area networks using proxy servers situated between local-area networks (LANs) and a backbone wide-area network (WAN). We develop a novel and effective video delivery technique called video staging via intelligent utilization of the disk bandwidth and storage space available at proxy servers. We also design several video staging methods and evaluate their effectiveness in reducing the backbone WAN bandwidth requirement. Our results demonstrate that the proposed proxy-server-based, network-conscious approach provides an effective and scalable solution to the problem of the end-to-end video delivery over wide-area networks.

Visual Constructor: Remote Authoring in a Web-based Learning System.

Abstract: This paper describes an authoring tool, Visual Constructor, that is being developed to help users without technical knowledge to create and organize World Wide Web-based course contents. The following goals of Visual Constructor are highlighted: (1) it does not require any knowledge of evolving Web technology; (2) the user interface is easy to understand and operate; (3) it is a Web-based remote authoring environment, so that authors can use a Web browser to accomplish all the tasks at any location; (4) course authors do not need to worry about the physical files; and (5) information can be updated or modified as course content evolves. The underlying methodologies that form the basis of the Visual Constructor authoring environment are summarized, including course layout templates, document templates, logical view, and physical file management. The hierarchical software modules are explained, and the authoring process is illustrated with an example. The three major features supporting presentation and navigation of a Web-based learning environment created by Visual Constructor (i.e., structural layout, service modules, and presentation flow) are described. The paper concludes with a discussion of future work. Three figures present the hierarchy of software modules, and screens for configuring the course layout and authoring the course content. Contains 14 references. (AEF) ******************************************************************************** Reproductions supplied by EDRS are the best that can be made from the original document. ********************************************************************************

Streaming video over the Internet: approaches and directions

Abstract: 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.

A survey of Web cache replacement strategies

Abstract: Web caching is an important technique to scale the Internet. One important performance factor of Web caches is the replacement strategy. Due to specific characteristics of the World Wide Web, there exist a huge number of proposals for cache replacement. This article proposes a classification for these proposals that subsumes prior classifications. Using this classification, different proposals and their advantages and disadvantages are described. Furthermore, the article discusses the importance of cache replacement strategies in modern proxy caches and outlines potential future research topics.

Proxy prefix caching for multimedia streams

Abstract: High latency and loss rates in the Internet make it difficult to stream audio and video without introducing a large playback delay. To address these problems, we propose a prefix caching technique whereby a proxy stores the initial frames of popular clips. Upon receiving a request for the stream, the proxy initiates transmission to the client and simultaneously requests the remaining frames from the server. In addition to hiding the delay, throughput, and loss effects of a weaker service model between the server and the proxy, this novel yet simple prefix caching technique aids the proxy in performing workahead smoothing into the client playback buffer. By transmitting large frames in advance of each burst, workahead smoothing substantially reduces the peak and variability of the network resource requirements along the path from the proxy to the client. We describe how to construct a smooth transmission schedule, based on the size of the prefix, smoothing, and playback buffers, without increasing client playback delay. Experiments with MPEG traces show how a few megabytes of buffer space at the proxy can substantially reduce the bandwidth requirements of variable-bit-rate video. Drawing on these results, we present guidelines for allocating buffer space for each stream, and how to effectively share buffer and bandwidth resources among multiple clients and streams.

Segment-based proxy caching of multimedia streams

Abstract: As streaming video and audio over the Internet becomes popular, proper proxy caching of large multimedia objects has become increasingly important. For a large media object, such as a 2-hour video, treating the whole video as a single web object for caching is not appropriate. In this paper, we present and evaluate a segment-based bu er management approach to proxy caching of large media streams. Blocks of a media stream received by a proxy server are grouped into variable-sized segments. The cache admission and replacement policies then attach di erent caching values to di erent segments, taking into account the segment distance from the start of the media. These caching policies give preferential treatments to the beginning segments. As such, users can quickly play back the media objects without much delay. Event-driven simulations are conducted to evaluate this segment-based proxy caching approach. The results show that (1) segment-based caching is e ective not only in increasing byte-hit ratio (or reducing total traAEc) but also in lowering the number of requests that require delayed starts; (2) segment-based caching is especially advantageous when the cache size is limited, when the set of hot media objects changes over time, when the media le size is large, and when many users may stop playing the media after only a few initial blocks.

Multimedia proxy caching mechanism for quality adaptive streaming applications in the Internet

Abstract: The Internet has witnessed a rapid growth in deployment of Web-based streaming applications during recent years. In these applications, the server should be able to perform end-to-end congestion control and quality adaptation to match the delivered stream quality to the average available bandwidth. Thus the delivered quality is limited by the bottleneck bandwidth on the path to the client. This paper proposes a proxy caching mechanism for layered-encoded multimedia streams in the Internet to maximize the delivered quality of popular streams to interested clients. The main challenge is to replay a quality-variable cached stream while performing quality adaptation effectively in response to the variations in available bandwidth. We present a prefetching mechanism to support higher quality cached streams during subsequent playbacks and improve the quality of the cached stream with its popularity. We exploit inherent properties of multimedia streams to extend the semantics of popularity and capture both level of interest among clients and usefulness of a layer in the cache. We devise a fine-grain replacement algorithm suited for layered-encoded streams. Our simulation results show that the interaction between the replacement algorithm and prefetching mechanism causes the state of the cache to converge to an efficient state such that the quality of a cached stream is proportional to its popularity, and the variations in quality of a cached stream are inversely proportional to its popularity. This implies that after serving several requests for a stream, the proxy can effectively hide low bandwidth paths to the original server from interested clients.