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View-Upload Decoupling: A Redesign of Multi-Channel P2P Video Systems

View-Upload Decoupling: A Redesign of Multi-Channel P2P Video Systems. Keith Ross. Polytechnic Institute of NYU. Today’s Talk. Overview of P2P Video Streaming View-Upload Decoupling (VUD): A Redesign of P2P Video Streaming Queuing Models for P2P Streaming. More Details…. Patent Pending .

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View-Upload Decoupling: A Redesign of Multi-Channel P2P Video Systems

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  1. View-Upload Decoupling: A Redesign of Multi-Channel P2P Video Systems Keith Ross Polytechnic Institute of NYU

  2. Today’s Talk • Overview of P2P Video Streaming • View-Upload Decoupling (VUD): A Redesign of P2P Video Streaming • Queuing Models for P2P Streaming

  3. More Details… • Patent Pending “View-Upload Decoupling: A Redesign of Multi-Channel P2P Video Systems”, Di Wu, Chao Liang, Yong Liu and Keith Ross, To appear in IEEE Infocom, Mini-conference, 2009. “Queuing Network Models for Multi-Channel P2P Live Streaming Systems”, Di Wu, Yong Liu and Keith Ross, To appear in IEEE Infocom, 2009.

  4. Today’s Talk • Overview of P2P Video Streaming • View-Upload Decoupling (VUD): A Redesign of P2P Video Streaming • Queuing Models for VUD Streaming

  5. 1 6 2 5 3 4 Peer-Assited Video Streaming • Peers redistribute video to each other • exploit peer uploading/buffering capacity • reduces load on server • Large scale deployments on Internet • thousands of live/on-demand channels • millions of world-wide users daily • Leading P2P Video Companies • CoolStreaming • PPStream • PPLive • Sopcast • UUSee

  6. PPStream (http://www.pps.tv) #1 P2P Video System in the World Developed by Liang Lei and Hongyu Zhang (China) in 2005. 350M installations ~12 Million active users each day Thousands of channels Num of Channels

  7. Common Features • MultipleChannels • Channel Churn • Heterogeneous Streaming Rates • HDTV Channels, VCR-quality channels,… • Heterogeneous Channel Popularities • Very few viewers in less popular channels. • Isolated Channel Design: ISO • Viewer only redistributes channel it is viewing

  8. Problems of Traditional ISO Design • Large Channel Switching Delay • Existing P2P video systems: 10-60 seconds • Large Playback Lag • Existing P2P video systems: 5-60 seconds • Poor Small-channel Performance • Inconsistent and poor performance in small channels. • Root causes: channel churn and resource imbalance

  9. 1 6 3 1 F A viewers 2 5 B E C F 3 4 C D Channel Churn in ISO Design Channel 1 Channel 2

  10. Channel Churn in ISO Design Drawback: distribution systems disrupted when peers switch channels 6 3 1 A viewers 2 5 B E C F 4 D Channel 1 Channel 2 after channel switching

  11. Resource Imbalance in ISO Design • Recall the instantaneous resource index for a channel of rate r with n viewers: • Ratio of available upload rate to required download rate • Channel in trouble if • Resource index can be imbalanced across channels • Small channels particularly volatile.

  12. Today’s Talk • Overview of P2P Video Streaming • View-Upload Decoupling (VUD): A Redesign of P2P Video Streaming • Queuing Models for P2P Streaming

  13. A Redesign of Multi-Channel System:View-Upload Decoupling (VUD) New Rule:each peer is assigned to semi-permanent distribution groups; independent of what it is viewing. distribution swarms channel2 substream1 channel 1 substream1 channel1 substream2 channel2 substream2 6 F 3 C 1 4 D A 2 5 E B viewers F D E 6 C 4 5 A B 3 1 2 Channel 1 Channel 2

  14. A Redesign of Multi-Channel System:View-Upload Decoupling (VUD) Advantage:distribution swarms not modified when peers switch channels distribution swarms channel2 substream1 channel 1 substream1 channel1 substream2 channel2 substream2 6 F 3 C 1 4 D A 2 5 E B viewers D E 6 1 C 3 4 5 A B F 2 Channel 1 Channel 2 after channel switching

  15. Advantages of VUD design • Channel Churn Immunity • Distribution swarms unaffected by channel churn • Cross-Channel Multiplexing • Distribution swarms can be provisioned and adapted to balance resource indexes across channels • Structured Streaming • Scheduling and routing can be optimized within the stable VUD swarms

  16. Key Challenges of VUD design • VUD Overhead • In ISO, peer only downloads video it is watching. • In VUD, each peer downloads its assigned substreams as well as the video it is watching. • Solution: substreaming • Adaptive Peer Assignment • Bandwidth allocation • Peer reassignment

  17. Simulation Experiments • Simulated features: • Channel switching • Peer churn • Heterogeneous upload bandwidth • Packet-level transmission • End-to-end latency • Zipf-like channel popularity • Comparison • ISO: using Push-Pull scheduling • VUD: using Push-Pull scheduling

  18. Simulation Parameters • 50 channels • Video rate 400 kbps each channel • Server rate 1 Mbps for each channel • 2,000 peers • Peer upload rates 128-768 kbps • Avg peer system time: 67 minutes • Channel churn follows IPTV study • 5 substreams per channel

  19. Channel Switching Delay Switching delay = time to acquire 5 seconds of new channel • VUD achieves smaller channel switching delay.

  20. Playback Lag • VUD achieves smaller playback lag.

  21. Today’s Talk • Overview of P2P Video Streaming • View-Upload Decoupling (VUD): A Redesign of P2P Video Streaming • Queuing Models for P2P Streaming

  22. Motivation • Develop a tractable analytic theory for multi-channel P2P live video systems. • Use model to study how to optimize VUD performance and perform bandwidth dimensioning • PS = probability of universal streaming = fraction of time resource index > 1for ALL channels

  23. Queuing Network Model • Each channel can be thought of as a queue • Each viewer as a customer • When viewer changes channels, routed to new queue • Customers move about channels independently: • infinite server queues • Let pij is probability of switching channel i to j. P = [pij ] • Let average sojourn time in channel j • Can do all kinds of cool things with this model! • Inspiration from the queuing and loss network literature.

  24. Closed Queuing Network Model • Peers never leave (e.g., set-top box peers) • Now just apply the standard closed Jackson network theory • Traffic equation • Relative channel popularity: • n is the total number of peers • Mj= # of viewers in channel j.

  25. Open Queuing Network Model • Applicable for systems with Peer Churn • Peers arrive at constant rate and join channel j with prob p0j • Peer leaves system with probability pj0. • In this talk, we focus on Closed Queuing Network Model.

  26. Analysis of VUD Design • Resource Index for substream s of channel j • Probability of system-wide universal streaming where and Mj= # of viewers in channel j

  27. Asymptotic Analysis of VUD • Under what conditions do all channels perform well when number of peers becomes large? • Fix number of channels J. • Let number of peers • Assume for simplicity no substreaming • Asymptotic regime: nj = Kj n • How to dimension Kj for large n?

  28. Asymptotic Analysis for VUD • Initially assume homogenous upload rates: ui = u. • Critical parameter: • Theorem: If α > 1, then PS goes to 0 for all choices of Kj. If α < 1, then PS goes to 1 if

  29. Asymptotic Analysis for VUD • Heterogeneous peer types: low uland high uh. • f = fraction of low peers (fixed) • Can find optimal peer allocations by solving: • If the value < 0, then PS goes to 0.

  30. Analysis of ISO Design • Let Mj be the random set of nodes viewing channel j. • Once again: • Can be solved used Monte Carlo methods and importance sampling.

  31. Asymptotic Analysis of ISO • Heterogeneous peer types: low uland high uh. • f = fraction of low peers (fixed) • Critical Value: • PS goes to 1if α≤ 1 and goes to 0 otherwise.

  32. Asymptotic Analysis: Example • uh = 4r, ul = 2r, f = ½ • r1 = 5r, r2 = r,ρ1 = .2, ρ2 = .8 • ISO: α > 1 • PS goes to 0 • VUD: • allocate high-bandwidth peers to channel 1; low bandwidth peers to channel 2. • PS goes to 1

  33. Numerical results • Results from analytical equations • 1,800 peers • 20 channels • ul = .2r and uh = 3r • Use asymptotic heuristic to dimension substream swarms

  34. Numerical Results • Probability of System-wide Universal Streaming (PS) • Vary Zipf parameter Many small channels

  35. Numerical Results of VUD Design • Probability of Universal Streaming in each channel Leastpopular channel • VUD achieves higher probability of universal streaming (PUj) in small channels.

  36. Refined Heuristic for VUD • Basic idea: equalize probability of universal streaming for all substreams: • Assume normal distribution for Mj • Use known mean and variance • Assume all streams of same rate r

  37. Refined Heuristics for VUD Num. of high-bandwidth peers in substream s of channel j Num. of low-bandwidth peers in substream s of channel j

  38. Refined Heuristic for VUD Streaming • Probability of universal steaming in each channel. • Refined VUD can achieve higher probability of universal streaming in small channels.

  39. Summary • Introduced a new design of P2P Video systems: View-Upload Decoupling (VUD) • Developed a tractable analytic theory to study ISO and VUD streaming • More insights about ISO and VUD designs. • Guidelines and Efficient Heuristics for VUD provisioning

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