1 / 15

Multimedia Proxy Caching Mechanism for Quality Adaptive Streaming Applications in the Internet

Multimedia Proxy Caching Mechanism for Quality Adaptive Streaming Applications in the Internet. Reza Rejaie Haobo Yu Mark Handley Deborah Estrin. Presented by Di Ma. Overview. Internet multimedia streaming apps using proxy better delivered quality faster startup

tex
Télécharger la présentation

Multimedia Proxy Caching Mechanism for Quality Adaptive Streaming Applications in the Internet

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Multimedia Proxy Caching Mechanism for Quality Adaptive Streaming Applications in the Internet Reza Rejaie Haobo Yu Mark Handley Deborah Estrin Presented by Di Ma

  2. Overview • Internet multimedia streaming apps using proxy • better delivered quality • faster startup • more adaptive than mirroring • Multimedia proxy caching • TCP-friendly congestion control is preferred • Quality of steaming is adaptive

  3. Architecture • Rate Adaptation Protocol (RAP) for CC • Hierarchical encoding for quality adaptation • If BWPC is high, popular streams can have higher • quality by prefectching c1 p s c2 Assumptions • All streams perform congestion control • bottleneck is the linkSP

  4. Delivering Procedure Relaying on a cache miss • Connections between proxy and client, server • and proxy are established • Quality is limited by bandwidth between proxy • and server • Replacement algorithm is used if cache space • is exhausted • The first client does not observe quality improvement • form the presence of proxy cache

  5. Delivering Procedure Prefetching on a cache hit Prefetching is demand-driven • Quality adaptation may attempt to send some • missing segments in cache PlaybackAvgBw <= StoredAvgBw PlaybackAvgBw < StoredAvgBw

  6. Delivering Procedure Challenge • Predict a missing segment that may be required by • quality adaptation Sliding Window Mechanism • Record playout time tp for each session • scan [tp+T, tp+T+] for missing segments • segments in new layer should be also included • prefetching be synced with playout rate • server side: new prefetching request preempts • the previous one

  7. Replacement Algorithm • Goals • average quality is directly proportional to popularity • quality variations is inversely to popularity • Replacement Pattern • Stream: Layer and segments • Victim layer, drop with granularity of segments • segments are flushed from end of layers

  8. Replacement Algorithm Popularity Function Weighted hit (per-layer) Popularity : how many past sessions are considered t: total sessions played so far

  9. Replacement Algorithm • Popularity table: • record popularity per layer for streams • Algorithm: • once the cache space is exhausted, the proxy flushed • the last segments of the least popular layer until • sufficient space becomes available.

  10. Simulations • Goals • qualitatively evaluate the correctness of this mechanism • verify if the mechanism satisfies design goals and how Evaluation metrics Completeness (per-layer) Continuity (per-layer)

  11. Simulations Request sequence generation Mth popular stream have requests where R: number of total requests N: total number of streams Assume different requests are served sequentially by proxy

  12. Simulations Results • Prefetching • goal: verify quality convergence • set cache to infinity (to disable cache replacement) • single client and single stream • bandwidthsp=56Mpbs, bandwidthpc1=1.5Mbps • 15 completed sessions

  13. Simulations Results Replacement • Goal: state of cache converges to an efficient one • Two factors: • Stream popularity ( BWsp<=BWpc ) • BW between client and proxy (BWsp> BWpc ) • 10 streams with lengths uniformly dist. bet. [1..10] min. • Popularity decreases with their index. • (stream 0 is most popular) • cache size = (total size of 10 streams) / 2

  14. Simulations Results Replacement • Effects of popularity • 95% of requests to high bandwidth client 1 • 5% to low bandwidth client 2 • Effects of client-side bandwidth • 95% of requests to low bandwidth client 2 • 5% to high bandwidth client 1 • Mixing together • 50% of requests to low bandwidth client 2 • 50% to high bandwidth client 1 • Note: impact of bandwidth may be less than str. popu.

  15. Conclusion Simulation-based evaluation of our mechanism reveals that interaction between the replacement and prefetching mechanism causes the state of cache to converge to an efficient state, in which the quality of every cached stream is directly determined by its popularity, and its upper limit is defined by the average available bandwidth between the proxy and its clients.

More Related